I know that just like a doctor's diagnosis, figuring out the source of an automotive problem involves picking away at the obvious. But its seems like with this example, they were into some pretty serious repairs, swapping out alternators and such. Perhaps a glance at the car's structure might have been in order? Seems like this is a classic example of every anti-best practice, from manufacture on the assembly floor to service in the shop.
I would hardly call a missing crankshaft bearing support 'obvious'. If the technicians had suspected the engine was assembled improperly or incompletely, my guess is that they would have replaced the engine and sent it to the engine manufacturer for analysis and tear-down. Even if they had a suspicion of a crankshaft support problem, I doubt they could have found it by dropping the oil pan for a visual inspection.
Glenn, how can they miss a part while assembling, that too crankshaft bearing. If it's a mistake from the service person, then obliviously they have to bear the expenses for repair and replacing the damage parts. Am not clear about when this story had happened; now a day's most of the service stations are automated and they used to maintain a check list for the spare parts.
Mydesign; First, I doubt it was the service person that forgot to install the bearing support. The engine was probably built at the Engine Plant, and then shipped to the Assembly Plant. At the Engine Plant this engine may have been partially assembled and then shift change happened, and the worker that continued to assemble the engine didn't notice the missing support and continued to the next step of the assembly. On the assembly lines that I have seen, one missing or extra part would not be noticed, especially not right away.
GlennA, how can we tolerate such ignorance from the service person? If they fail or ignored in tightening the brake screw, what will happens to the passengers. Moreover, most of the service centers are offering one or two test drives at different levels, before delivering the vehicle. This can make sure that your vehicle is in perfect condition.
MyDesign; Seriously ? How many times do you think a service technician gets a problem like an engine assembled but missing part(s) ? This is possibly a once-in-a-lifetime scenario. But now they have the benefit of experiencing this arcane problem. Also, many repair shops are now flat-rate. Hopefully the tech was hourly and got paid for the time spent on this problem.
MyronB; You want to run the engine without the water pump ? How will you cool the engine for the duration of the testing ? Actually it is not simple cooling, as the thermostat is probably set to open at about 180 F. so it is also an operating temperature issue.
How many people responding on this post to criticize the tech have real-world experience doing car repairs vs. second-guessing ?
Good question, but recall that a test for vibration takes but a few seconds, so starting with a cold engine should not cause any problem at all. Keep in mind that dragsters (top-fuel class cars running nitromethane fuel and superchargers putting out several thousand horsepower) use no coolant at all. Yes, I know they only need to run for the burn-out, staging, and a 5-second race, but as I said, testing for vibration only needs a few seconds.
GlennA says "I doubt they would have noticed it (missing main bearing cap) even if they dropped the oil pan"
Really Glenn? did you mean "I'm SURE they would have noticed a missing main bearing cap if they had dropped the oil pan."
...because I absolutely cannot imagine a competent mechanic pulling an oil pan and not noticing a missing main bearing cap! That's like going to a dentist complaining of "finding some blood in my mouth and a sore place" and him not noticing that you have a tooth knocked out.
Ockham; Part of my comment was that a missing main bearing cap would be a rare occurence and not an obvious problem to look for. Since you believe the missing part would have been obvious, please forward a picture looking up into the engine from below with the oil pan off.
Beth, good observation. I have had lots of excperiences like this, although I was doing the wprk myself. After replacing a number of parts it tuens out that a major assembly has a problem that one did not expect. Once it was a cracked head. The push rods were bending. It turns out tha the head had been milled to raise the compression. This was a valid performance enhancement on another type of engine, but not on the one I had (an MG B). So, similar to the leaving out of a bearing, my friend had done something that was not valid. I treated the symptoms, not the disease. This is all too easy with an internal combustion engine.
Good observation, Chuck. Quite amazing. I wonder if the car company would take responsibility for this even outside of a warranty. Seems this type of error would extend responsibility to the car maker even outside the standard warranty.
< I wonder if the car company would take responsibility for this even outside of a warranty. Seems this type of error would extend responsibility to the car maker even outside the standard warranty>
Reminds me of an incident in a major motorcycle magazine in the 80's. It was the bad old days of Harley-Davidson. The magazine bought a bike anonymously for a long-term test of the product and dealer support. They got to evaluate dealer service pretty quickly...the bike had a mysterious vibration that a string of dealers were unable to diagnose. The magazine finally tore down the bike themselves and figured out the crank was assembled with two LH weights! H-D refused to honor the warranty since the engine was serviced by an unauthorized party!
The major national mag did a scathing article, H-D pulled their ads for awhile, and I'm sure the two actions lost the Motor Company thousands of prospective customers!
I remember that if you bought a Harley, you had to buy 2 = one to ride and one to strip for parts. And the local Harley distributor was convicted of being the ringleader of a price fixing scheme with other motorcycle shops. I have also been told that Honda is the abbreviation for "Harley Owners' Need Dependable Alternative". The last time I had my Moto Guzzi at the motorcycle shop I was looking at the Harley's and Gold Wings. One of the staff commented that the new Harleys had improved so much they were almost as good as a Honda. Harley does make a nice bike, but I just can't justify the premium paid for the name.
@Rob- From what I've heard, Harley customer support is pretty good nowadays. The problem the magazine had was in the 80's...I believe HD was owned by AMF at the time, and it almost put them out of business.
Fortunately, it was still under warranty. This was quite a while ago - I think the engine was a 350. 350's were (and are) pretty tough motors. You really have to beat on one to hurt it. I've watched people try to blow them up (no oil, no water, full throttle - for an hour). It still ran. Smoked a bit though...
Pretty tough to diagnose this sort of thing. One always assumes that things are built correctly in the first place, and something has gone wrong.
Where should one start when diagnosing a vibration like that? When do you give up and pull the motor? I wouldn't want to be the one to make that call.
I once changed a water pump on the 350 in my Suburban. The motor shook like crazy with the new pump. How much rotating mass could there possibly be in a water pump? Evidently enough to shake the motor. A real GM pump solved the problem.
Many years ago (too many to admit) I worked for a local Heathkit Electronic Center on the "Jiffy Bench". I would take a look at kits that customers couldn't get to work, and try to fix them 'in a jiffy'. Usually it was just crappy soldering.
Sometimes, it was a bit more involved, and they had to sit in the Service Dept. for a few weeks before we could look at them.
One thing about fixing a kit - you must use a totally different approach to problem solving, as you could never assume that it was built right in the first place.
Some true horror stories (and some very funny ones) were generated in that place...
One kit I fixed had horrible soldering, but had worked for 25 years (poorly). I re-soldered everything, and turned it on. Bad idea. Some of the wiring mistakes weren't actually there due to bad joints. It blew up when I turned it on. Oops.
The clue was lower than normal oil pressure in addition to vibration; though one might suspect an oil pump or oil pressure relief valve issue before an internal leak (e.g. a missing crank bearing shell, block casting pinhole/crack into an oil gally) in the oil distrubution system, and might reasonably suspect two unrelated problems, one in the oil system another in rotating part balance. A missing bearing shell is a pretty unlikely cause, though *perhaps* could have been caught if the pan and perhaps valve covers too were removed to investigate the oil pump and distribution system).
Clearly though once broken and the missing bearing shell was found, assuming prior engine overhauls this is clearly a manufacturing defect, even if beyond the usual drivetrain warrenty when the problem (engine drive train vibration at sertain RPM's) was first logged.
I find it hard to believe it didn't have this problem from day one, let alone some point in time 'down the road'. With the bottom cap missing, the lower half of the bearing shell would also be missing. This would lead to an immediate lost of oil pressure. I can't remember for certain, but I believe the center bearing has a radial groove for oil distribution, and is also the one responsible for end play float.
Article leaves out what year impala this is... if it was a late model, I guarantee it wasn't a 350... and it's also front wheel drive.
Someone needs to find a new Service Crew! That's the trouble with having service personnel diagnosing engine issues. Since the advent of the "crate engine" no one gets inside the engine anymore. They replace the entire engine. There is very limited understanding of the engine design and it's operation.
In this case the low oil pressure is the overriding clue (as it so often is). There is only one thing in a Priority Main oiled engine that can cause the oil pressure to behave that way. In all modern engines the oil pump design is capable of producing far more oil volume and pressure than there is demand, by-passing the reserve.
With a full understanding of the design and operation of the engine the first thought that came to my mind was crankshaft.
BTW, 350 Chervolet engines use the 5th main bearing as the thrust bearing, not the 3rd.
Thanks for your thoughts. The driver transistor is a diamond package 2N3055 NPN that uses a mica insulator. It looked good but, may have a flaw or puncture that would result in path to ground that could destroy the 2N3055, the small signal NPN, and the regulator chip. I'll replace the blown stuff and install a new mica insulator. I'll let you know what happens. Thanks again for the tip.
Kleetus, I agree with you. It would seem as if this car would be unlikely to survive very long this way. Yet the issue of warranty has not been mentioned, which makes me think it lasted quite awhile. I don't understand.
To clear up a few things - this was a new, unmolested car - but this was 1970 or thereabouts - well before computers took over service departments. The main bearing caps were all installed - just the lower bearing shell from the #3 main journal was missing.
The upper shells in 350s have a groove, the lower shells are solid. There would obviously be a leakage path at the ends of the groove, but as mentioned, the pumps in 350s can put out a lot of oil. It's also likely that the upper bearing shell turned slightly, which would at least partially cover the oil passage in the block - in which case there would be minimal, if any loss of pressure.
The only thing that stops bearing shells from spinning is the crush between the upper and lower shells. No lower shell, no crush. There are tangs on them, but they really don't do that much, other than as assembly aids.
I don't think that a missing bearing could be construed as a common occurrence, so a service tech could be forgiven for not considering it as a possible cause. A weak bypass spring in the pump, or even a piece of crud stuck in the bypass valve could cause the low oil pressure. I don't know exactly how low it was, but it was evidently high enough to dissuade them from pulling the motor.
The engine lasted about 6 months from new before the crank broke. If it was run at higher RPM, it would probably failed sooner, but this was a family car - it probably never saw more than 3000 RPM in its life.
And yes, it was fully warrantied, and probably would have been even if it had lasted past warranty.
If it had a forged crank, they would probably never have found it, as it never would have broken.
In about 1979 I designed a system at Sun Electric, for installation on engine test stands as part of the new engine hot test system, that examined amplitudes of engine vibration at the crank, canshaft, and firing frequencies. It was determined that the system would detect any missing bearing part in the V-8 engine 100% of the time. The customer declined to purchase this option, even though it did work very well and was both reliable and not very expensive. A missing bearing half is a fault that gets very expensive to repair as soon as the engine is installed, but the claim was that it was so rare that there was no economy in checking for it. Go Figure.
To xti: May I digress here? The readers have made good comments on the shaking engine to which I really can't add, so I'd like to ask xti a Heathkit question. Do you recall working on an IP-2715 regulated power supply? I am repairing one for a friend. It has good unregulated DC output, but no regulated DC. The output transistors are OK and by injecting a current into their bases I get an output voltage. I replaced the blown driver transistors and replaced the blown regulator chip (no longer available) with a 741 op amp and modified circuit. The supply worked fine for a while and then the chip and drivers blew again. Perhaps they are overloaded trying to deliver the required base current to the output transistors. Components and soldering job all check OK. Heathkit forum contributors say the supply was a piece of junk from the get-go and to s-can it, but I say it's worth salvation--it seems well-built and the transformer is husky with plenty of copper and iron. I don't want to re-invent the wheel, but unless you have any helpful hints, I'm ready to redesign it from a series-pass transistor system to a switch-mode design.
We never had any of these come in for service, so I don't have any direct knowledge of them. They seem to be very simple, and should be rock solid, though. Heathkit very rarely built turkeys, and I don't think that was one of them.
We did however, have a power supply with a similar problem that eluded us for quite some time. We were never ones to give up on a problem, though.
This supply would run unit it got hot, then it would blow the output fuse. Nothing we tried worked.
As ridiculous as it sounds, the Service Manger finally decided to tear the unit apart - all the way to its individual bits and rebuild it from scratch - using only the components that came out of the 'carcass'.
He shredded it, grabbed a manual, and rebuilt it from the ground up, testing every single part as he put it back in.
As he went to mount the output transistor on the heatsink, the manual said to install it using a mica insulator. There was no insulator in the pile of parts.
It turned out that the original builder had neglected to install the insulator. Every time we tested the output transistor, it was fine, so we never took it off the heatsink.
The heatsink was black anodized, and therefore technically non-conductive, however there was a tiny burr on it that would evidently short the collector to ground - but only when the sink got hot enough to expand a little bit.
A huge amount of energy went into this repair, which could - and probably should, have taken no more than 5 minutes on the jiffy bench.
The moral of the story? - ALWAYS look for the most complicated possible causes first. It's more fun that way, and guarantees you will have a job for some time to come. Just don't tell anybody what the real problem was when it turns out to be the first thing you SHOULD have looked at.
Make sure that the outputs are the correct Heath parts. They may have been swapped out for devices with higher drive requirements.
We did have a run of TI MJ-802 output transistors in AR-1500 receivers that did not meet spec. We had to go into every kit in stock and put in a giant red notice, along with a bag of new Motorola replacements to prevent the ensuing carnage if the TI ones were used.
It wasn't practical to remove the TI ones from the package, as they were buried too deep. I never saw any kits come back because of this probem, so I guess everyone read the notice.
It's possible that the same thing happened with the IP-2715. The 2715 came out toward the end of my time with Heathkit however, so I'm unaware of that actually being an issue.
A friend has the entire HEATHKIT "PROFESSIONAL" rack & panel series of stereo equipment that he built in the 1970s, 1980s. Some of the chassis are in need of repair, including the midrange speakers. He claims that he had the name & tele. # of a former HEATHKIT technician in Michigan, who had a "side business" repairing HEATHKIT products. My question to you is, do you know anyone who currently is knowledgeable in legacy HEATHKIT products that he can send the items for repair & retuning?
The problem with the speakers is that the polyurethane foam "spring" at the edge of the cones has disintegrated, and so the speakers do not reproduce the sound correctly anymore. However, he told me once that there is a local speaker repair shop, so addressing that problem is not an issue. But, he doesn't want to invest in the speaker repair until he gets the remainder of the electronics repaired.
IF my memory serves me, they have the AM-FM tuner, the preamp, active crossover chassis, the base crossover, & two final amplifiers, one for the large bass speakers & the 2nd for the midrange & tweeter speakers. The speaker enclosures are the (6ft) tall cabinets that HEATHKIT sold.
Wow - this seems to have turned into a Heathkit thread. I don`t know of anyone that still fixes Heathkits personally, but Heathkit still exists, and they apparently still have most of the manuals available. Go to Heathkit.com and send them an email.
They do not have repair parts, and do not repair old kits, however.
There seem to be lots of people that do repair old Heathkits, though. Just do a search online for `Heathkit Repair`.
Once you have the manuals, any decent tech should be able to repair one, though.
Speakers are easy to repair, you can also get foam repair kits online or through eBay.
A cautionary note to your friend, though. If the power amplifiers are the large 200W per channel ones, DO NOT ship them anywhere with the power transformers installed.
The transformers will tear out of the `chassis` and destroy the amplifier.
Personally, I wouldn't even drive them across town with the transformers installed.
A minor drop in the Living room can also be disastrous. They have a wire frame chassis that was an incredibly stupid piece of engineering - I don`t know what they were thinking. It seems to be made from old coathangers.
These amps also have an unusual output stage configuration. It is essential that you have a manual before attempting repairs.
The best thing to do with these amps is save the nice front panel and trash the rest of it.
Put the panel back in the rack and hide an old JBL 6260 or 6290 behind it. Your ears will be in heaven. 6200`s were some of the best amps ever made.
xti: THANX very much for that info. I will pass it on. I do not know if they have the manuals yet, although comments were made that he did build all of this equipment from the kit products, and not as preassembled units. I know the amplifiers are heavy, and sit at the bottom of the 19" cabinet, but I do not know about the "internals" of the power amps. Although he was an excellent engineer in his day, they are older now, and I know he doesn't have any test equipment beyond a simple V-O-M, so I suspect that he'd just as soon send the units to someone w/ the proper audio generators, o-scopes, etc. to tune & adjust as necessary.
Regarding the speakers, I know he's already checked w/ a shop in this area, who specializes in speaker reconing, etc. I believe they told him to bring them in for inspection, and that IF they thought it would be more economical to replace w/ new ones than to recone the old ones, they would advise him.
Although the internet can be a GREAT "device" for searching, it can also be a giant black hole! I've gotten totally frustrated more than once myself doing google searches, only to end up with 4,000 "hits", NONE of which led me to a solution. I guess my online persona, OLD_CURMUDGEON is indeed a very accurate description. When it comes to manufacturers' product specs, I can't tear myself away from a printed catalog!
xti: Your comment above was funny ... the one about how this blog has morphed into a HEATHKIT subject. I suspect that there are more people who've experimented with building various HEATHKIT products in the past 40+ years than those who have had the center main bearing cap of their 350 Chevys missing!!!!! Now, IF it was a "4-bolt main" motor w/ a forged steel crank, ala Camaro & Corvette, then I suspect it might be still running! (Ha! Ha!)
I know HEATHKIT is "back in business", but it ain't the same HEATHKIT as we all knew so fondly, and therein lies the difference. I wonder how many HAMS are still using some of the those transceivers (SB ***), etal.? Or their scope kits, etc.?
To xti and OLD CURMUDGEON: Hmmm..... morphed into a Heathkit thread? True enough, but thanks to Design News we have this freewheeling exchange of ideas and subjects, and we've all had a chance to meet, albeit virtually. By the way, I haven't yet tried the suggestions; with our local (Chicago area) weather so nice, my wife somehow co-opted me into helping get our little garden ready for planting, etc. I did find some other Heathkit forums, and one suggested that an LM317 is a better substitute for the unobtainable Heath regulator chip.
Morphing back to engine vibration, it seems the repair guys could have disconnected the external rotating components by unhooking the fan and accessory belts first. This would eliminate the alternator, water pump, smog pump (if equipped), power steer pump, and air conditioning compressor as a vibration source. That would leave the transmission and engine as a vibration source. Then, carefully block the engine, and unbolt the tranny, and run the engine. If vibration remained, it would then be isolated to the engine. If vibration went away, then the trans was the likely culprit. Watcha think?
Morphing back to the Heathkit, I recall many years ago, my boss said, "We need a two channel, precision DC-coupled scope for product development, so I bought a Heathkit, and you put it together!" At that time we were doing some pioneering work in solid-state alarm and telemetering systems and the 'scope would be handy. Anyway, I built the 'scope, and it worked OK, but ironically it had to be sent to a facility with a precision 'scope for calibration! Between the kit cost, my labor, and the calibration and shipping, we would have saved time and money with a commercial oscilloscope.
I think that this happened so many decades ago that it doesn't matter what they SHOULD or SHOULD NOT have done. But, continuing this thread leads me to suggest that the proper plan of attack should have been to call a district CHEVROLET troubleshooter into the discussion, who maybe would have suggested a different plan for attacking the vibration problem, instead of wasting precious time, resources & parts on "maybe" fixes. All the auto companies maintain a cadre of highly qualified supervisory personnel to deal with the esoteric & arcane problems that arise with auto diagnosis.
On a personal note regarding this situation, I had an uncle who purchased a new Cadillac in the early 1960s. The vehicle never ran correctly from day one. With 472 cu. in. under the hood, it should have flown, but didn't. He brought it back to the dealer for service. They kept the vehicle for the better part of a week, testing everything they could think of. Then, they called a Cadillac troubleshooter, who inspected the vehicle. While it was on the lift, with the engine running & a mechanic in the driver's seat, this troubleshooter was under the vehicle observing the operation. As he passed by the rear of the vehicle, he noticed that the exhaust on one side was far more pronounced (volume of air. NOT sound), so he directed the mechanics to disassemble the entire exhaust system all the way to the exhaust manifolds. What did they find? Well, they found a 6 1/2 oz. green COKE bottle stuffed in one tailpipe near the inlet to the muffler. They removed it, reassembled the exhaust system, and delivered the vehicle to my uncle's estate. The family drove the car for several years WITHOUT a hint of a problem! The ONLY question remained, "was it a Monday car or a Friday car?"
To OLD CURMUDGEON, you are correct about woulda, shoulda, etc. being moot. The real value of our discussions is that it adds to our knowledge base so that we hopefully don't repeat those earlier mistakes, But, (loud sigh here) human history is littered with repeated blunders, hence fallen bridges, burst dams, and yes, even a few wars.
Wow! They replaced a waterpump, steering pump, alternator, and a whole bunch of other stuff before figuring this out? Man, sounds like they took your credit card for a ride. Hope all those replaced parts didn't cost you a cent. Sounds like an afternoon of poping the oil pan off and inspecting the crank and bearings would have solved the question of the day.
As far a crate engines goes, I'd say they have become popular because no body knows how to rebuild an engine and if they do, it's hard to find an engine machine shop.
John; When you are troubleshooting, do you replace the most difficult and most expensive part first ? I start with possible adjustments, working through the most likely and the most easily replaced parts. Only after the easy and cheap stuff didn't work, would I look at the difficult and expensive stuff. However, that does not mean changing parts for the sake of changing parts = the part must be related to the problem.
Even if one of the tech's was a paranormal, that does not mean that the missing support would have been readily visible with the oil pan off. Monday morning quarterbacking is always easier.
No, I don't always get the diagnoses correct the first time, but I know an accessory on the engine wouldn't cause erratic engine speed unless it was locking up completely of which is going to burn the belt up. A flat spot on the crank can cause engine vibration and even noise. Anyway, I think a mechanic would know right away if one of the accessories was having a problem by simply spinning the pully with the belt off and feeling for roughness. No doubt, it is a unique problem that you wouldn't expect a new engine to have and probably not the easiest problem to solve since your probably looking for a hair line crack somewhere on the crank.
John; What about the clutch on the air conditioning compressor ? It engages and disengages with the demand for cooling, and can be also be configured to disengage on heavy acceleration. So that is not a fixed load. I don't know how much load variation there would be from the power steering pump between straight ahead vs. turning. Are you getting an intermittent load from the power brake booster vacuum draw ? I think this problem was before serpentine belts and belt tensioners, but there is still the possibilty of a bearing running freely when cold and binding when hot. Many problems seem simple, but then you get down into the weeds and the finer details come into play.
According to an article in today's ELECTRONIC DESIGN blog by Louis Frenzel, HEATHKIT has once again closed shop. So, it would seem that the euphoria is short-lived. Too bad, too, since having such companies might help to reinvigorate the investigativeness of the young mind. Of course there are others in this market, some doing quite well, so one has to wonder, 'what was wrong with the new HEATHKIT'S business model?'
That's sad to hear that Heathkit is gone again. I loved it when I was a kid, as well as many other science and engineering toys -- erector sets, chemistry sets. My guess is that kids now take a software approach to innovation play. We can see from Gadget Freak that kids are incorporating smartphones into their engineering play. Don't know if Heathkit could have kept up with that.
From Louis Frenzel's post: "Yet other do-it-yourself companies like Make and SparkFun are doing well."
My question remains, 'what was wrong with the new HEATHKIT'S business model that they failed?' IF you read NUTS&VOLTS magazine with any regularity, you'll see that kitbuilding IS alive & well, AND very sophisticated. Although much of the magazine is devoted to coding & using the new-age microcontrollers for robotic projects, there are many other entries which do NOT fall into that category. So, on the face of it, it would seem that HEATHKIT wasn't targeting the modern audience for their product line.
Because HAM radio has become so specialized, it's easy to understand why building a "ham shack" nowadays means going to a catalog of manufactured products. Even the stalwarts of the industry, EIMAC for transmitting tubes, is long since gone, so it's become a challenge to assemble component parts. Consider the stereo industry, another HEATHKIT profit center. No one builds components anymore. It's too easy to go to WAL*MART or some other outlet for an off-the-shelf setup.
In other arenas where HEATHKIT dominated, those markets do not exist any more. For example, home entertainment equipment. With the home theatre phenomenon, WiFi, DVRs, etc., there's nothing for them to sell in kit form. Plus, the sophistication of modern equipment no doubt would make any offerings very limited in functionality. And, finally, in test equipment, you have the same phenomenon. For someone truly interested in electronics research & hobby, one can buy excellent test equipment at ridiculously inexpensive prices. Why would anyone want to spend untold hours assembling an analog 100 MHz o-scop, when a 1 GHz digital scope can be had for very little?
Since we're morphing around, try this one. And no, you can't read ahead to see what the problem turned out to be. Mainly because I'm not going to tell you until we see what the "masters" would have done to solve the problem.
Lets see how long it takes someone to figure it out.
The things I will tell you are simply facts about the vehicle, or where / how it was driven. They may or may not have anything to do with the actual problem.
Here we go:
Vehicle in question is a 1973 Chevrolet Monte Carlo with a 275 HP 350 engine and TH350 transmission. Car is totally stock. I purchased it used (from a GM Dealer) in about 1975 with approx 40,000 miles on it. I live in Vancouver, BC. It rains a lot here.
The car was used as a daily driver.
I drove the car for approx. 10K miles, and decided to do a few minor upgrades to it. I installed a set of Hedman headers (hooked up to the stock dual exhaust), put in a bit more cam, installed a Cloyes True Roller Timing Chain, an MSD 6A Multi-Spark ignition, upgraded the cap, rotor, wires, etc., and installed the big Goodyear Wingfoots and 15x8 rims off of my '69 L88 Corvette. (I had just blown the 10th rearend out of it and decided to park it for a while)
Nothing terribly special, but it made a noticeable improvement in performance, and dramatically improved the handling and appearance. It may have increased the power by 50-75 HP over stock. Not a lot, but a nice little bump.
I didn't tear down the transmission, but I pulled the pan, and didn't see anything nasty, so I just put in a new filter and fluid. I probably put in a shift kit - can't remember for sure.
The car ran fine for about 15,000 miles. I drove it all over the place - even down to LA and back with no issues at all.
One day, it seemed that the power was down a little bit. Hardly perceptible, but down nonetheless. Maybe lost 5-10 HP, but hard to quantify. Might just have been one of those days.
The next day, it seemed a bit worse.
By the end of the week, it was very noticeable, and was starting to piss me off.
A week later, the car was a dog, and would barely get out of it's own way.
It got so bad, I had to avoid steep hills. I eventually had to park it, as it was no longer useful as transportation.
Basic symptoms were - push down the throttle, and bugger all happens. You might as well push on the brakes for all the good it did.
A cursory inspection of the engine, air filter, transmission and exhaust system revealed nothing. No smoking guns to be found.
What would you have done to figure this out?
PS - it's perfectly acceptable to ask any diagnostic question you want.
PS - If anyone happens to guess the correct answer right away, I'm not going to let on - to give other people a chance to chime in with their thoughts on the matter. Don't ask if such-and-such was the problem. Tell me how you would go about diagnosing it.
Since you say nothing happens when the throttle is pressed I am assuming the engine speed does not increase - rev up. First thing to check is the throttle linkage and the carburetor butterfly. Manually actuate the butterfly. Check the fuel system - is the carb getting gasoline; fuel filters, fuel pump pressure and flow.
Rob Spiegel; I was replying to xti's tangent on the Monte Carlo problem. I don't think it was a crankshaft issue also. I doubt that I would have identified the missing crankshaft bearing support before the engine died.
Timing is good, mechanical advance works as expected. Ignition system checks out OK. (MSD 6A's will easily fire plugs gapped at .150 - even if they're immersed in oil.)
- PS if you ever work on a car that has an MSD ignition - be EXTREMELY careful. NEVER go near the plug wires with the engine running; and NEVER even go near the PRIMARY side of the ignition unless the battery is disconnected. Experience is speaking.
Brakes are fine. Parking brake is fine. Car rolls very easily.
Engine does not miss, backfire, or run rough. Just has no power. Starts easily hot or cold. No strange noises in the engine, no vibrations. Oil pressure is fine. Temp is fine.
So where are all the people that were telling us how they could have found the missing bearing in 15 minutes, and how dumb the mechanics were to be changing all those parts?
C'mon guys - step up and tell us how to fix the Monte Carlo. No wild guesses - only a methodical, reasoned approach is allowed.
I will even give you a hint. Three things that troubleshooters often seem to ignore in favour of a purely technical approach. What, When, and Where. But you have to ask the right questions. Customers rarely recognize that something they did might have caused a problem. Oops, did I just see a cat run out of that bag?
If nobody seems to be getting warm, I'll define exactly what I mean by those terms.
GlennA - thanks for playing along. At least someone has big enough, er, "dual, low-hanging, spheroid" objects to step into the fray.
Nice to see some activity here. Thanks for taking the time to think about it. I should mention that I will take the suggestions as they come in and try to relate them to what we did at the time to solve the problem. It`s likely that someone will (or maybe even has) come up with the cause of the problem, but I`d like to expand on exactly how the potential cause should be diagnosed as well, as some tests that might have helped us diagnose it faster were either difficult or impossible to perform. (At least for us at the time, being backyard mechanics with limited access to cool test stuff)
GlennA: Aha! Another Cleese fan, I see. Nice!
LoKi; MyronB; We checked the fuel system and the filter in the QJet. Pressure was OK in the shop, but we had no way to test it under load, as it is a steel fuel line all the way to the carb, and I didn`t want to cut it to install a fuel pressure gauge that could be used on the road. The thought of running a rubber fuel line to a gauge on the outside of the car didn't thrill me very much, either.
I tried to think of some way to test the fuel pressure under load, and realized it was really only a matter of trying to figure out whether the float bowl was full or not. Holley carbs have little sight plug holes in the bowls to check fuel level, but no such hole in QJets, and the bowls are buried too deep in the carb to drill any.
I thought about swapping the QJet for a Holley (I had about 50 of them at the time), but I couldn't find any of my Holley to QJet adapters for some reason.
The accel pump was working. I had rebuilt the carb when I did the engine work, and I did (past tense) know my way around a QJet. Secondaries were fine, and the vacuum pot was functioning correctly.
I have to admit to removing all the evap stuff, so that wouldn`t have been a problem. Good call on the gas cap. But we swapped it for a new one (of the correct model), but it made no difference.
We shall say for the purposes of this discussion that the fuel and ignition systems were not the cause of the problem.
GlennA; Good call on the transmission. I did have a car that exhibited similar problems, and it turned out to be the torque converter. But not on this car. The trans, converter and rear end were all fine. Fluid was clean and didn't show any sign of burn.
CRITIC: We checked the compression, it was fine across all cylinders. We considered exhaust problems, so we pulled the mufflers, shook them, and peered inside them. There were no strange noises coming from them, and no evidence of visible problems, but without cutting them up, there was really no way of being certain.
The pipes appeared to be fine, and were very solid when hit with a hammer. The outside of the pipes had some surface rust, but were in great condition, so we moved on. The headers were inspected, and showed no signs of damage. (I have seen low hanging headers crushed before, but these ones had no such damage).
We looked up inside the pipe to the header, and didn't see any problems, but we couldn't see past the first bend in the pipe.
Being a 1973, it didn't have any cats. We considered trying to measure backpressure, but were unable to think of any way to do it, and weren't sure what measurements to expect even if we could figure out a way to do it.
I'd like to expand on this thought though. How would you test for restriction? We will assume the mufflers are OK. The car has true FACTORY dual exhaust with no crossover pipe. All components seem to be in slightly rusty, but otherwise excellent condition. No visible dents or holes anywhere from the headers to the tips of the tailpipes. If memory serves me correctly, the system had 2 1/4" pipes. Might have been 2" though.
What might explain the cause of such a restriction? Remember, this was a gradual loss of power. It didn't happen overnight. It took between several weeks and a month to kill the car. There was only a barely discernible difference from one day to the next, and it would always start and run fine at idle. It did seem to deteriorate much faster as it approached the end, however. Sort of an exponential curve.
It should be mentioned that we had retained the stock cast iron intake manifold when we changed the cam, and used new factory gaskets when we re-installed it.
I sprayed some ether around the edges of the manifold, but the RPM didn't change, so we discounted manifold leaks as the problem. We also figured that any leak big enough to kill the engine would have killed the idle as well.
Bob Salter - I had a 1987 IROC Camaro that was running crappy. I asked the dealer how they went about figuring out what the problem was (remember, these cars had computers, but with very limited diagnostic capabilities).
Their answer? "We just keep throwing new parts at it until the problem goes away". At which point I asked - who pays for the parts that didn't fix the problem? Answer - "You do".
xti; This is now beyond my depth. But I do have a guess. You didn't say whether the engine rev's when in drive, or what happens with the rear wheels off the ground. You did say the transmission, torque converter, and differential were okay.
My guess is that there is a vacuum line between the transmission and the engine that reduces engine power during transmission shifting. In neutral the engine doesn't care, but in drive it would need that handshake. So that vacuum line was blocked, pinched, or disconnected, leaking, so the engine was at 'no-power' thinking the transmission was shifting (forever).
Thanks for staying in the game. Interesting guess. The TH350 transmission does have a vacuum modulator line that goes from the intake manifold to the transmission. It basically changes the shift points and shift 'ferocity' according to engine vacuum. The lower the vacuum, the later the shifts, and the harder the shifts. The thinking was that if the manifold vacuum is low, then you probably have your foot in it so to speak, and you would probably want it to shift harder and later.
But it's only a one-way system, and the line has a very small orifice at the end of it to limit the speed of the vacuum signal. Even if the line came off the transmission, it wouldn't affect anything other than to make the transmission shift very hard and very late.
If it came off at the motor, it would create a vacuum leak that might affect the engine's operation slightly, but it wouldn't change over time.
Good try, though.
If you re-read my last post, the answer was actually correctly guessed, but I'd like to give our group of shadetree mechanics a fling at a final diagnosis of cause and effect before I cap off the story.
It's back to what, when and where.
What & when is a mid 70's GM vehicle with a basically stock exhaust system that shows no outward signs of trouble. Where - is Vancouver, BC - famous for our rain. And the attendent puddles it generates. Some of them can get big. And deep.
So how did these things conspire to gradually kill our car?
The saga will end tomorrow night - even if nobody figures it out by then.
Sounds like the same problem my folks had with a 1967 Buick LeSabre, one section of the exhaust was double wall pipe and gradually the inner wall collapsed (rusted) enough to restrict airflow. It was a insiduous problem that none of the dealer mechanics had ever seen before. It took a long time to track down that problem.
I've seen a variant on this theme with rebuilt engines where somebody align bores one of the crankshaft main journals off center from the others, and again you get a crank that flexes on every rotation. The ultimate failure is similarly spectacular.
For a few years now folks have been using the horizontally opposed six engine for the Chevy Corvair in aircraft applications, and crankshaft failure is a similar concerne there, partially because the crank and bearings weren't designed for thrust loading (which is what a propeller will put on it) and because there's a pretty big moment arm involved when you're swinging 75" of propeller instead of turning 24" of transmission flywheel.
After a few crank failures in that application, it wasn't long before somebody went back and designed an engine add-on to solve the problem:
Ok, I'll take a stab at this. You've said it's not a fuel or ignition problem, so I'll assume timing is ok too. Compression was good, and from what you're telling us it sounds like exhaust restriction was to spec. A cam lobe may be slowing wearing away, but this would only affect one cylinder (never heard of all the lobes going flat) and I doubt one cylinder down on power would have this much of an effect.
The timing chain could be stretching too causing valve (and hence ignition) timing to be retarded more and more, and it's finally slipped a tooth or two? I think you mentioned it had a "racing" type double roller timing chain didn't you? I hate those things - they might be stronger than a stock factory chain and maybe the chain doesn't stretch as much, but the teeth depth is much shallower, so just a little bit of stretch will make those type of chain sets skip a tooth. Yes, I know that from experience - the durability on those double rollers is lousy. I've seen them fail in 10K-20K miles A stock factory chain & gear has really deep teeth, and the chain has to stretch a lot (and usually the nylon on the nylon coated ones has to be mostly chipped off) before it'll finally skip a tooth.
You hint that water intrusion might be the culprit. I've experienced this on a high performance fuel injected car (86-87 Buick intercooled turbo) where the owner had installed a high flow cold air intake which sucked in air from under the bumper and had driven through pouring rain. The air filter was soaked and was throwing water on the mass airflow sensor causing it to read inaccurately. However, since this is an old school carburated engine with an old school air filter above the carb, I can't imagine it getting soaked or being able to throw enough water down the carb to cause the issues you're seeing.
But, staying with your water intrusion hint, the factory air cleaner housing had a Thermac didn't it? This is the thing with a flap that redirected the air intake from the normal path to sucking air off the exhaust manifold when the engine was cold (to try to get warmer air into the carb). So maybe the Thermac was corroded so that it was stuck in that position, and maybe the air hose to the exhaust manifold was crushed or blocked with debris and the engine was starving for air?
That's my best guess given the available info. Looking forward to hearing what the answer is!
After rereading your hints about the deep puddles and the exhaust, did you perhaps park with the tailpipes immersed in a puddle, and when you shut her down maybe it sucked a bunch of water into the muffler, causing restriction? But I'd think any trapped water would just push out with a few revs of the engine. Just grasping at straws based on your hint.
If water has nothing to do with it, I'd go with the stretched timing chain / skipped teeth. Been there, done that!
I may have missed this in the various emails, but did you lads check the camshaft? Gradual power loss may be the result of camshaft/lifter incompatibility (camshaft was changed, as I recall) resulting in cam lobes so worn that they can't open the valves.
Also, was cam and crank timing checked? A worn timing chain may result in the chain jumping a tooth or more resulting in retarded cam timing. The result is reduced low-end performance, but noticeably perky high rpm performance. You would find that the distributor would have to be advanced every time the chain jumped a tooth. After a while the cam timing would become so retarded that the engine would not start or run very weakly if it did.
I had first hand experience of these very symptoms on a 1971 Dodge with a 318 ci V-8 that used a plastic-coated cam gear that started to degenerate at the 125,000 mile mark. I presume this coating was for quiet operation, like the infamous Flathead Ford molded fiber cam gear.
Another thought here; was there good oil flow to the lifters? Low oil pressure could result in collapsed lifters and again, valves don't open or open a very small amount. Forget this idea though, if you changed to solid lifters with the camshaft change.
Myron – I once worked on a mid 60's Pontiac Parisienne (the Canadian version of a Bonneville, but it was actually just an Impala with different sheet metal). It was owned by one of my neighbours - she was an Avon Lady (hint). It had incredibly low mileage, as she only drove it from one house to the next one, and then eventually, drove it home.
It was a 275HP 327 with a QuadraJet carb. The car had NO power.
I started it up in her driveway, and it was virtually silent. I wasn't absolutely sure that it was even running. About the only way you could tell it was running was listening to the squeak of the fanbelt, and noticing that the fan was turning, albeit VERY slowly.
If you opened the throttle, you were rewarded with a sigh, and a barely perceptible increase in engine RPM.
For some reason, I decided to pull the valve covers, and started the engine again. The rocker arms were, well, wiggling. Sort of. Most were moving up and down no more than 1/4", some not at all.
I pulled the intake manifold, and saw what appeared to be the most perfectly crafted valley cover I had ever seen. It was an exact duplicate of the underside of the intake manifold.
This was a phenomenal find, as I had never seen one like it before, at least not one this well crafted. I had no idea that GM had ever made anything like it, and was very curious as to why they would bother.
It fit so perfectly into the block that there were no spaces around it to even lift it out.
I took a screwdriver and attempted to insert it between the block and the "cover".
It wasn't a cover at all. It was BLACK GOO 6" thick.
She had never changed the oil in the car since it was new – just added more. The car had probably never reached operating temperature even once in its entire life due to her driving habits.
The cam had no lobes on it at all. Some of the lifters were worn so badly that the valves inside the lifter were literally hanging out the bottom, as the bottom of the lifter was completely worn away.
Thanks for giving us the chance to exercise our little grey cells, as Detective Poirot would have put it. Brain teasers have always been with us as the following story will show.
Years ago I saw this story in a 1910s-1920s era automotive (maybe SAE) magazine. I apologize for not being able to give full attribution, but I believe it to be true.
It seems this auto manufacturer was developing a new engine for a new model car. The prototype engine was set up on a test stand to run it in before dyno testing. The order was given to fire it up and the engine seemed to crank and crank until it fired up. It ran fine for a while, then huffed and puffed and died. This happened two or three more times and the enginers and mechanics went into their full diagnostic mode just as we have all tried to do in xti's mystery. It was to no avail as the engine did its crank & crank, fire up & run, and puff & die show.
The order was given to tear down the engine. All parts seemed to be in spec, and while head-scratching was going on, a mechanic started to pick up and look at, and measure, and touch the parts. After some time, he discovered that the camshaft gear had extra teeth so that there was no longer a 2:1 ratio between the crankshaft and camshaft. After cranking for some time, the cam would come into correct phasing with the crank, and the engine would fire and run. It ran long enough to run itself out of phase and the engine would die. A new camshaft gear with the right tooth count solved the problem!
Best regards to all and enjoy the Memorial Day weekend,
xti: the gradual loss of power tells me that there is probably an exhaust restriction, such as a clogged catalytic converter. However, I would start by running a comprssion test, and if the compression is OK, then check for exhaust and intake-air restrictions. If compression and airflow are good, then the next step would be to check the air/fuel ratio under power. Ignition timing could also be a concern, and should be checked as well (probably before the fuel mixture) at all RPMs.
Since other factors, timing, ignition, etc., seem OK, I suspect the problem may be in the fuel system. If this is a fuel injection vehicle, I would check the pressure in the injector fuel rails. If low or non-existent, I would check to see if the in-tank pump is running or the in-tank filter is clogged; remember, if the engine doesn't start, the fuel pump will run only a few seconds. These are not easy to check, I know.
If carbureted, check for (usually mechanical) fuel pump pressure and also the small filter at the fuel inlet to the carburetor. Also, for either fuel system, check the fuel tank evaporative emission controls and fuel tank venting. Without venting the tank won't flow. I would also check the engine air filter as well. And, oh yes, you did check to see if there was fuel in the tank, right??
I think that Myronb is on the right track, the problem may be with the fuel system. Check to see if there is water in the gas. Pull the main fuel filter and dump it into a container, water should show up readily.
Check to see if the accel pump in the Qjunk carb is functioning.
I would check for vacuum leaks, it sounds as if it may be running lean under load. Are the secondaries opening too soon on the carb?
This story does the heart good of this do-it-yourself and tinkerer when Mr. Goodwrench can't figure out the cause of a problem and who's diagnostic is to throw parts at the problem hoping one of them will be the solution. This makes me wonder how many times this method was applied to cars out of warranty and the owner was charged for every single part plus labor.
Haven't read through all the posts but I would have thought the oil pressure light coming on would have been a clue. One reason I like a pressure gage versus a light (or too late light) is that you can monitor the actual pressure.
I suspect if the oil pressure was checked you would have seen low oil pressure throughout the rpm range.
I've seen several people noting that the mechanics would have noticed a missing main bearing cap if the pan were pulled.
All the main bearing caps were in place. Only the center main bearing lower shell was missing. This part is only about 1/8" thick, and is completely hidden by the cap.
The only way to see if it was installed would be to remove all the main bearing caps.
But this infers that the mechanics should have expected this type of problem.
I highly doubt that more than a couple of the more than 1 million small block Chevy engines built ever suffered from this error.
To have a mechanic consider a literal 'once in a million' chance as an occurrence that should be investigated first seems to be asking a bit much.
How many of us would have connected a slight low oil pressure issue with a vibration problem anyway?
It would seem far more likely to me that some out of balance rotating part would be the culprit, as the oil pressure variance was evidently within reasonable tolerances. With no lower shell to hold it in place, the upper bearing shell may have rotated enough to partially block the oil passage in the block, making the loss of pressure relatively small. Maybe they cured the light by increasing the idle speed slightly.
The oil pressure might have been considered a separate minor problem that would be figured out after they cured the vibration.
What if the oil pressure light was burned out? Then how would you diagnose it? Who would even consider checking oil pressure when looking for a vibration?
I can hear it now -
Customer: "I have a vibration".
Service Tech: "OK. We'll tear the motor apart and look for missing bearing shells. I've never heard of it happening, but let's look there anyway - I'm sure GM will understand and pay us for our time."
As someone who has owned, raced and worked on a fair number of small and big block Chevrolets I just have to disagree with the idea that this is some mysterious problem beyond an experienced mechanic. On a sbc/bbc with low oil pressure symptoms coupled with deep engine vibration the very FIRST place i would look would be the bottom end. A properly working s/bbc oiling system is pretty robust. No i would not trust the light. I would do what my 1966 factory service manual said. If low oil pressure is suspected, Install a temporary mechanical gauge and ascertain system pressure". When i saw the 6-7lbs oil pressure at idle, that would be it. Bottom end trouble. And yes, I can guarantee you I would spot a missing main cap - even laying under the car. I have a 427 and a 454 out in the shop right now and if you buy the gaskets and pay the labor I'll be glad to shoot the demo photo and post it up.
The missing bearing shell WOULD be hard to see - but i wouldnt find it by looking for it anyway. See, the low oil pressure and the vibration would scream to me "main and/or rod bearing issue" so it wouldn't matter WHAT the issue was. It would be found in the tear down - because any small or big block Chevrolet with a deep engine vibration and low oil pressure's got a bottom end problem and that babies coming out!
Of course I don't just post about them - I actually work on them.
This one had me scratching my head too. Nothing we tried seemed to be getting us any closer to a solution.
After 'exhausting' every other possibility, the only things left that we couldn't absolutely verify were the fuel level in the float bowl under load, and the remote possibility of a restriction somewhere in the exhaust system.
QuadraJet carbs have a composite float, and I have seen them soak up fuel and sink too low, so we put in a new one to be safe. No change.
I decided to remove the mufflers and fire up the engine to see if the mufflers were somehow plugged up.
The sound that came out of the theoretically 'open pipes' was anything but what I expected.
There was a weird whistling / hissing sound along with the expected open exhaust sound.
As the engine was revved, the hissing sound nearly drowned out the open exhaust sound.
I shut down the motor, crawled under the car, and took a very close look at the two roughly 5' long pipes between the headers and the mufflers.
I realized that one was dead round for it's entire length, but the other one was slightly oval for about 12" in the middle of the pipe. It was only about at most, 1/2" out of round, but it was noticeable.
I grabbed a hacksaw and cut the pipe off about 1/2 way through the 12" long slightly oval section of the pipe.
What I saw completely dumbfounded me.
The pipe was standard mid 60's-mid 80's GM double wall construction (a fact that I knew, but discounted as having anything to do with the problem).
Even though the outside wall of the pipe was virtually untouched, the inside pipe was completely crushed flat. As an example, take a 3" diameter x 1/4" wide rubber band, and put it inside a similar 1 1/2" diameter rubber band. The loop it forms looks exactly like what the inside of my pipe looked like.
Except my pipe was much worse.
Evidently, I had at some point driven through a deep water puddle. The sudden cold shock on the outside pipe had caused it to contract. The inside pipe was still hot, and had nowhere to go, so it buckled and separated slightly from the outside pipe. When the pipe cooled overnight, there was a small gap left between the walls of the pipe. This meant that a slight vacuum formed, which of course pulled in moisture-laden air to fill it back up.
The next morning, the moisture flashed to steam and, since it was impossible to stretch the outside wall, it further enlarged the space by crushing the inner pipe a little bit more.
Every time the car was parked, the cycle would repeat. As the space between the pipes grew, larger and larger volumes of 'wet' air were drawn in, and when it flashed into steam, the inner pipe was rapidly crushed until it was completely flattened against the outer wall.
The only reason the engine ran at all was the fact that I had re-used the stock intake manifold and used stock gaskets to put it back on. These manifolds have a heat riser passage that connects one exhaust port of each head together. Normally, there was a thermostatically controlled valve on the passenger side exhaust manifold that forced all the exhaust on one side of the motor to go through the intake manifold to the other side when the engine was cold. This was intended to prevent icing of the carburetor in cold weather.
Ironically, if I had used an aftermarket aluminum manifold, the engine wouldn't have run at all, as they usually don't have a heat riser passage in them.
Thank you all for trying to wrap your heads around this. For me, it was simultaneously one of the most frustrating, but ultimately rewarding diagnostic sessions I have ever experienced.
I have a 2000 Mustang with 3.8-liter V6 engine and automatic transmission that had about 180,000 miles when it gradually developed a severe vibration. The vibration could be felt with the car parked or while driving, but it was worst at about 1,200 RPM.
I was being sent out of town on a long business trip when I decided to take the car to a Ford dealership to have the vibration diagnosed. I called several local Ford dealers, trying to find one that had a vibration analyzer. In the hands of a trained and experienced technician, a good vibration analyzer can help determine the approximate location of the vibration, and in some cases pinpoint the cause of the vibration.
I dropped the car off at the dealer, and after a couple of days, they called and said that they wanted to replace the engine mounts, which were a little cracked. I knew that the mounts were not the cause of the vibration, but I let the dealer replace them to the tune of $450, so they would proceed with the vibration diagnosis.
I soon found out that the service manager had lied about having a vibration analyzer. They disassembled the front of the engine to inspect the balance shaft and its drive chain. They also replaced the torque converter and flex plate. They were kind enough to only charge me labor for the remainder of the diagnosis, returning the old torque converter and flex plate to the car after they discovered that these were not the cause of the vibration. After they burned through another $400 in labor, they gave me their diagnosis of the problem: they had isolated the vibration to the engine. Their solution was to replace the engine with a rebuilt one, which I thought was not necessary, so when I returned from my business trip, I drove the car home.
I removed the engine from the car, removed the rotating assembly (crankshaft, rods, pistons, flexplate, and harmonic damper) from the engine, and took it to a machine shop to have its balance checked. The machine shop quickly found the cause of the vibration.
Would you care to guess the cause of the vibration, or offer what would have been your proposed diagnostic plan? Did I really have to disassemble the engine?
Sometimes flexplates or torque converters have welded on balancing weights that can come off, but that would give you a sudden, rather than a gradual increase in vibration - besides, they replaced them with no improvement.
A quick inspection of these parts usually shows spot weld marks surrounded by nice clean metal that indicates the former presence of such welded weights.
My guess as to a gradual increase would be that the outer ring of the balancer had come loose from the rubber liner and was rotating relative to the crank.
If this is an internally balanced motor, not much would happen if this occurred, however if it is an externally balanced motor, all hell would break loose as it rotated.
The outer ring of these balancers typically have an intentional out-of-balance condition built into them to counteract the natural out-of-balance condition of the motor. There would most likely also be weights welded to the flexplate.
That is about the only way I could think of that would cause a gradual increase in vibration.
Oil on balancer + 180,000 miles = deteriorated rubber. The hint would be the broken motor mounts - that rubber came apart as well. The vibration of the motor probably helped kill the mounts and the balancer even faster than normal.
Another possiblity is that the damper turned relative to the crank due to a sheared key. Some engines don't even have a keyway anymore, although that's pretty unlikely with an externally balanced motor.
xti: the motor was running fine, except for the vibration. It was not misfiring. There were no strange noises. Oil pressure and coolant temperature were normal. There was no loss of power. The vibration developed over a period of 3 - 4 months.
I did not check the ignition timing because it is a "distributorless" ignition system, and there is no timing adjustment.
I'm not familiar with that particular motor, but since you've apparently ruled out the damper and flexplate, I can't think of anything in crank, rods or pistons that could cause a gradual increase in vibration over a period of several months.
Cranks are typically balanced by drilling holes in the counterweights, and I doubt there are any counterweight eating bacteria around, so that's out.
Rods are either pressure cast from powdered metal (pre-balanced) or forged and ground on the ends for balance. Nothing I can foresee would gradually change the weight of any of the rods. Unless the aforementioned bacteria developed a propensity for munching on con rods.
Pistons are one piece, and unless the rings are slowly disintegrating, I can't see them gradually changing weight either. If they were coming apart, you would hear it or lose power.
I think you would have noticed any loose con rod or main cap bolts when you tore it down.
If a bearing or wrist pin was going away, you would have heard it.
The only thing left that I can think of would be a bent crank, but that seems even more unlikely than the bacteria solution.
Is this an even-fire V6 with offset crank pins, or an odd-fire with straight crank pins? I have seen offset journal cranks crack in the area between the two offset bearing surfaces, but it's extremely rare, and usually causes a lot more problems than just some vibration. And I think you would have noticed if the crank came out in two pieces.
If the problem was with the crank, rods or pistons, you've got me on this one.
My first move in diagnosis would have been to drop all the belts off the motor, and fire it up to see if anything had changed.
I then would stick it on a scope and see if the firing pulses were showing up at the right times.
Assuming that nothing was found, and assuming the engine was running normally, inspection of the flexplate and converter would probably be next on my list. If I suspected the convertor for some reason, I would unbolt it from the flywheel, push it back out of the way and fire the motor again.
Assuming it was still vibrating, I would re-inspect each balance weight location on the flywheel to make sure it was still there.
After that, I would probably try a new balancer before tearing into things any further.
The next step would necessitate tearing down the motor, but with 180K on it, it's probably time for a new one anyway, and it's rarely economical for a dealer to rebuild an old motor, as rebuild shops can do it faster and usually much cheaper.
You might be able to rebuild it cheaper yourself, but only if you value your time at zero $/hr. and aren't impressed with the concept of warranties.
New rings, pistons, bearings, gaskets, seals, grind the crank, grind/replace the valves/seats, bore and deck the block, reface the heads, new valve springs, new injectors, new cams, new timing chain & gears, new oil & water pumps, etc. etc.
Add up all the parts and machining costs, add some $ for your own time, and methinks a rebuilt motor (with a warranty) is probably a better bet.
But I'm still very curious as to what the problem was. Other than it being a Ford, that is...
xti: depending on how you set up the 'scope to check the ignition pulses, you may have found the problem. It turned out that the outer ring of the harmonic balancer had spun relative to the inner part of the balancer. This was not at all obvious from looking at the balancer. When the machine shop checked the balance, they called me and asked me to bring them the engine front cover, so they could see where the timing pointer on the cover was relative to the TDC (0°) mark on the balancer. When we saw that the TDC mark was about 40° from where it should have been, it was apparent that I needed to replace the balancer.
If I had checked the ignition timing, it would have been obvious that something was wrong with the position of the timing marks, but there was no reason to check the timing, as it is not adjustable and the engine was running fine (other then the vibration).
I now know that I should not believe a harmonic balancer is good just because it looks good- the angular position of the outer ring has to be checked as well.
When I re-assembled the engine, I did not bother to make it "like new;" cylinders and crankshaft journals were still within Ford acceptable dimensional limits. I simply honed the cylinders and replaced rings, bearing inserts, and gaskets. It cost me about $650 for parts, including the new balancer and a new front cover, which comes with a new (external) oil pump. I had to replace the front cover because the Ford dealership broke it- they neglected to remove one of the lower bolts, which is hard to see, so when they pulled on it, it broke, leaving part of the cover attached to the block. When they put the cover back on, they just gooped up the fracture with RTV and didn't bother to tell me they had broken my car.
The balancer would be about the only thing that could cause a gradual increase in an unbalance condition. Any other scenario (other than a loose bolt in the bottom end) would cause a sudden, not a gradual change.
Some new engines don't even have a timing mark on the balancer, so it would be almost impossible to spot a rotated outer ring unless the ring had moved 'horizontally' as well (towards or away from the engine).
About the only way to tell if it was bad would be to put on a new one and try it.
Sounds like your Ford dealership needs some troubleshooting lessons. And they might have considered reading a manual before destroying your timing cover.
Many years ago, I had a minor vibration issue with the 450 HP 327 in my '64 Chevy II. I had recently installed a 5500 RPM stall speed torque converter on my TH400, and had noticed a slight vibration at about 7500 RPM that wasn't there before.
It was pretty minor, though, so I didn't worry about it. Bad idea.
A couple of weeks later, as I took it past 7500 RPM (I know, young and foolish) there was a rather spectacular explosion. Metal shrapnel ripped through the floorboard and firewall, smashed the distributor, cut the transmission cooler lines, and littered the street with chunks of metal and transmission fluid for two blocks.
This converter was only 8" diameter, and had three 1/2"x1"x2.5" long steel tabs welded to it, which I had attached to the 11" flexplate with 1/2" L9 bolts.
The tabs broke off the converter, spun around on the bolts, blew the entire front of the transmission housing off, then the tabs and bolts ripped through the flexplate and came up through the floor of the car.
Great fun. One piece came through the floor directly under the gas pedal, blew it in half and hit the bottom of my boot. Fortunately, they had super thick soles on them. I'm lucky that I didn't lose a foot...
They later redesigned the mounting for these converters to use a continuous laser cut ring instead of separate tabs. A nice touch, but little overdue unfortunately.
I still have the car - with the hole in the floor - but it hasn't been on the road for nearly 30 years. Maybe someday...
Yes, he did. His was quite a bit more spectacular than mine, but my adventure was distressing enough for me...
Along with numerous other ones that were also a bit nerve wracking.
Here's a new vibration puzzler for you:
Car - 1964 Chevy II (somewhat relevant)
Engine 450 HP 327 (also somewhat relevant)
Colour - Blue (totally irrelevant)
Car is at dragstrip. Launch car @ 5500 RPM stall (new converter), reach 7500 RPM, shift into 2nd; reach 7500 RPM, just about to shift into 3rd, when there is a loud bang, (a bit hard to hear above the open headers, but audible); and small hole appears in the hood about 18" to the left of center, 30" in front of the windshield.
The ensuing vibration scared the crap out of me, and caused me to abort the run immediately. Which really sucked, as it was the best run of the day to that point.
At idle, there was no vibration at all. As the RPM was increased, the vibration got REAALLY bad.
xti: well, the hole in the hood seems like it would be in line with a cylinder. However, any scenario I can think of, all of which involve pieces of the engine penetrating the hood, would cause vibration at idle as well. It seems like only parts of the rotating assembly would have sufficient momentum to penetrate the hood. I give up on this one! I am not very good at diagnosing vibrations anyway! What happened?
Don't feel too badly that you didn't get it right away. I think it took me the better part of a day to figure out what had happened.
Early GM alternators have a fan blade assembly that consists of a flat piece of ~18g steel with the outer diameter bent back into a bunch of little blades that act as airfoils that pull air through the alternator. Sort of like a shallow, one-sided squirrel cage fan.
The fan is sandwiched between the alternator pulley and a step on the alternator shaft. The back surface of the tips of the blades only clear the body of the alternator by about 1/8" - if that.
The blades are not connected to each other at the tips, and some of the blades are slightly larger than others - probably to stop any possible harmonics that might be generated at certain RPMs.
The stock alternator pulley has a diameter of slightly less than 3".
The stock crankshaft pulley has a diameter of approx. 7", giving a ratio of about 2.5:1. If the engine is doing 7500 RPM, the alternator is doing nearly 20,000 RPM.
One of the larger blades was bent outwards slightly by the extreme RPM, and contacted the end of the bracket holding the alternator onto the motor. The blade was immediately ripped off the fan, and exited the scene by punching its way through the hood.
The missing blade threw the fan out of balance, and shook the crap out of everything.
At low RPM, the out of balance condition was not noticeable, as the blade weighed virtually nothing.
It took a quite while to figure out what caused the hole, as there was no obvious source for it.
Every time the engine stopped, Murphy's Law ensured that the spot on the fan with the missing blade would hide at the bottom of the pulley out of sight, of course.
Who would even think to look for something like a blade missing on the alternator fan? I certainly didn't.
If it hadn't punched through the hood, I would probably have been driven mad trying to figure out where the vibration was coming from, as there would have been no clue as to the source.
(I guess my guardian angel had a strange sense of humour that day. I'm certain that I have one, because I'm still here after doing many totally inane things...)
Racers often put larger diameter pulleys on the alternators, and smaller diameter pulleys on the crankshaft to lower the RPM of the alternator to save power. It turns out that it also stops fan blades from coming through the hood.
I guess I was lucky the entire armature didn't explode. That could have been very messy, as it is quite heavy.
The next weekend, my car was proudly sporting new pulleys. But I left the hole in the hood. It was too good a conversation piece. Besides, it was too expensive to fix anyway.
Just another one of the joys of having a car with too much horsepower. But they're great fun, even with all the inevitable carnage...
My basic motto in life: If some is good and more is better, then too much is just right.
At least at the dragways that I used to visit, modified cars were not allowed to compete unless they had an adequate scattershield. I don't know if that would have helped in your situation, but it did allow for drivers walking away from cars with blown up clutches on several occasions. Scattershield and roll cages are our friends.
Yeah - I always used a scattershield on manual trans cars. One is supposed to use a scatter blanket on autos, but they only encircle the main body of the transmission anyway, so it wouldn't have helped in this situation.
They also restrict airflow around the trans, and make it a bear to work on. Who would have expected that a little 327 in a street car should need one anyway?
Maybe some monstrous big block (which went in the car later...) - but not a little mouse motor.
A friend nearly chopped his '56 Chevy in half when his clutch exploded. There's a pic on the net of the inside of a '55 that looks almost exactly like his car looked. Just type in 'clutch explosion', and you should find it.
Looks like someone took one of the old style 'rip the top off the can' style can openers to the dashboard.
Scary. Fortunately, he somehow made it out in one piece. The first thing he bought for his next car? You guessed it.
Re: Engine vibration thread that morphed into a Heathkit thread:
To: xti and others who have tried to help on my repair of a Heathkit IP-2715 power supply.
(Please see the morphed thread from around 05/13/2012) I was able to get this old supply going by redesigning the regulator and driver circuits. I removed the dead and unobtainable Heathkit regulator chip and the low-signal NPN pre-driver and associated components from the Heath PC board. I installed components I chose onto the modified board.
I used a Texas Instruments LM317 voltage regulator chip to feed the base of the 2N3055 driver transistor which is Darlington-connected to four paralleled power transistors. By the way, I did replace the (fractured) mica insulator under the 2N3055 transistor. I used the equations in the application notes to calculate the values of fixed resistors and a voltage adjustment potentiometer. The supply works just fine now. I plan to make my circuit modification available on a Heathkit forum for all users of this Heathkit power supply.
Critic; On a tangent, I also had dealership problems. My 1980 Dodge Omni was diagnosed with an ignition computer problem. Before the repair shop sent it to the nearby dealer, they specifically asked if they had a replacement in stock, and they (supposedly) did. The dealership replaced the Hall Effect sensor and said it was fixed. I went to pick it up, and of course it wouldn't start. I had to drive across town in a borrowed car on a rainy Friday night to get a computer from another dealer to fix the car. I did get some consolation that the mechanic that did the repair was checking the ignition, standing in a puddle. When the engine stopped cranking, the ignition fired and 'lit him up'. And the shop manager went up one side of the dealership service manager and down the other for taking the job without having the computer. I also was told that a couple of other customers that had been referred to the dealership for a failed ignition computer returned to say the computer was not the problem, some other repair had been done. At which point the shop manager pointed to the shiny new ignition computer under the hood. Dealerships don't make profits from warranty ignition computer replacements, but they do from other work.
My dad told me a story years ago about a guy that bought a new olds but it seemed to be burning a lot of oil. Turned out some of the piston rings were never installed. That one must have been assembled on a Monday or Friday.
Yes, I remember that notion in the 1970s, Ratski, where you were supposed to avoid cars that were produced on Monday or Friday. Not usre how you swere supposed to determine that. I also remember the very real sabotage that occurred when workers were unhappy.
Surprised they didn't take an engine oil sample and send it out for used oil analysis. That would have easily shown elevated levels of iron, copper and lead in the oil from the crankshaft and bearings which were being destroyed... or if any other engine component was damaged, it would have a contaminaiton signature in the oil as well. Bad head gasket, you'd see glycol/coolant in the oil. Bad valve, bad sparkplug, weak compression - would likely show up as fuel in the oil from that cylinder misfiring. This is pretty much standard practice in industry...guess we can't expect the 'SAE Certified' monkeys to do the same.
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