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Made by Monkeys

Design Flaw Rusts Rear Mounts

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Beth Stackpole
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FMEA important design step
Beth Stackpole   2/2/2012 7:08:28 AM
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Great real-world example showcasing the need for engineering teams to seriously address Design Failure Mode Effects Analysis--a process that perhaps isn't as robust as it should be on many a development effort. You were lucky that you had enough ingenuity and engineering smarts to troubleshoot and handle this problem on your own. Most people wouldn't be so lucky.

naperlou
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Re: FMEA important design step
naperlou   2/2/2012 12:47:07 PM
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It is interesting that in the automotive world that this type of FMEA is not done more completely.  As Beth mentions, quite charitably, the process was not as "robust" as it should be.

Some of your examples ring very familar, although most of my early experience was with small British sports cars.  My first car had a leak on one side of the oil pan (the passenger side).  That side had no rust.  The other side had rusted through and a previous owner had used some old road signs to replace the rusted out floor pans.  As this was under the carpet, I didn't see it at first.

I do notice cars I have bought in the last decade or so have much better corrosion resistance, and I live further north where they use lots more salt.

David12345
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Re: FMEA important design step
David12345   2/2/2012 3:40:18 PM
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Ironically my experience with automotive floor pan rust was usually from the inside out.  either the windshield frame would rust until it leaked or window seals would leak.

Cars with carpeting would get wet carpet then dry-out.  Cars with rubber matting would get wet and stay wet until the floor pan rusted out (from the inside as I said with my experience).

And yes, newer cars seem to do much better with rust-proofing.  I don't know if it's from the body design or processing with an immersion pool of rust proofing primer or zinc/cold galvanize, but most cars have better rust performance since the late 1970's.

 

Tim
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Rust spots
Tim   2/2/2012 6:41:12 PM
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As a kid in the '80's, we had a Chevy Citation which had its share of issues, but the main thing we saw was that after the first few years, there was a spot in the center bottom panel of the driver's side door that would rust out every year before the annual inspection requiring a fiberglass patch.  The next year, the patch would be gone and you would need a bigger patch.  In watching the car run, there was just enough room beneath the front mud flap for a small stream of rock salt to hit the exact location of the rust spot.  The solution was longer mud flaps for our car, but I remember seeing a lot of similar Citations with the same rust spot.

Charles Murray
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Good engine
Charles Murray   2/2/2012 8:02:53 PM
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I drove a car with that engine for six years and never had problems with it -- maybe I didn't own it long enough. I liked the engine. I chose it instead of a 3.8-litter because I heard the 3.8 had head gasket problems.

wade
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Bronze
taurus subframe mounts
wade   2/3/2012 10:09:53 AM
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i've worked on these type of parts for 20+ years and the requirements for corrosion have evolved due to technological advances in surface chemistry, litigation from accidents due to corrosion, and overall advancements in customer expectations of quality.

i'm sure the dfmea process was done and the vehicle level testing was done by ford, but sometimes this type of corrosion doesn't show up until some time has elapsed.  hence the galvanized washers added as a recall.

i think you will find that designs over the last 5-10 years are much more robust due to the lessons learned on these previous models

i'm glad you were not driving when the mounts failed.

David12345
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Re: Good engine
David12345   2/3/2012 10:34:21 AM
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I too heard that the higher performance 3.8 liter engine had some reliability issues.

I have VERY good engine experience with a 1985 Taurus Company car and this 1987 Taurus Station Wagion that I later bought BOTH with the 3.0 liter engine.  I drove the Station wagon until it had 156,000 miles and the enginer was still running well when I traded it in.  The transmission was on it's last legs at that point with poor shifting and sometimes slipping. 

I would buy a car with that 3.0 Liter engine again in a heartbeat.  It looked good, ran smoothly, had good performance, was low maintenance, was easy to maintain, got 22-26 mpg and was reliable. What's not to like?

David12345
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Re: taurus subframe mounts
David12345   2/3/2012 10:52:05 AM
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Wade,

From a Design perspective, I for one would be very interested in more detail about the "technological advances in surface chemistry" you mentioned.

Additionally, as an automotive and motorcycle enthusist, I would like to use some of that knowledge for more robust restorations and upgrades on my personal projects.

I feel that the galvanized washer upgrade by Ford was a simple and very good technical solution to that particular problem.  I was disappointed about the poor implimentation diligence of this recall on ALL the affected vehicles; since, this was clearly a significantly dangerous potential failure to the running gear.  I was not informed about it prior to the failure, and the video I found on the internet of a man changing the rubber bushing on the same model car also did not have the recall upgrade installed.  I would venture to say that likely MANY of these vehicles never had the upgrade installed.  A great upgrade only works to the extent that it is implemented.

OLD_CURMUDGEON
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Platinum
VEHICLE RUST
OLD_CURMUDGEON   2/3/2012 10:58:51 AM
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In late 1975, I purchased a new TOYOTA CELICA "Fastback".  To those who remember, it was very much akin to the original MUSTANG fastback.  At any rate, this vehicle was garage-kept, 95% of the time when not in use, since we lived in one of the northern states, prevalent to winter storms, snow, sleet, rain.  On about the 3rd year of ownership, I noticed the large rubber gasket which sealed the rear hatch was loose when I opened the door.  So, I attempted to place it back onto the flange lips.  (The flange lips were created from the inner sheetmetal & outer sheetmetal panels, and spotwelded along their length for strength & bonding.)  In doing so, I discovered that there was no flange present at all.  So, I continued to remove more of the gasket, until I had most of it in my hand.  When observing the gasket more closely, in the cavity of the gasket was a very long coil spring which was designed to rub up against the flange, providing the necessary grabbing force.  Additionally, this cavity was full of rust!  That was the turning point for us.  Since the flange was non-existent due to total corrosion failure, I made a "sneaky" repair, undetectable to the naked eye, and traded it in on a 1980 DATSUN 200SX, a fun car to drive, which I drove for 4 trouble-free years before realizing that it would be best to add a 4-wheel-drive vehicle to the stable.  And, so we sold the DATSUN to the next-door neighbor's oldest son, and bought a 1984 FORD BRONCO II.  ANOTHER GREAT vehicle!!!!   

bob from maine
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Platinum
Re: VEHICLE RUST
bob from maine   2/3/2012 11:32:52 AM
I have experience destructive corrosion on a number of vehicles and it is evident that every year the auto manufacturers use a new/different steel alloy to enhance ductability, increase the cycle life of the dies, improve paint adhesion; some years Ford has a winner for rust susceptability, some years they lose. Most suspension components are uncoated and apparently not designed to outlast the painted metal elsewhere on the car. Northern states have started using a liquid substance that greatly lowers the freezing point of water in much smaller concentrations. This substance cannot be allowed to remain on uncoated metal, it is much more active than Sodium or Calcium chloride. If you want to keep your $20-30K automobile for 200,000 miles, wash it every other week during winter. It is small insurance. The rule of thumb for cars in the 40's through 60's was to wash weekly, wax every 4-6 months, re-paint every 4-5 years, do an engine "freshen" every 50K miles and you could expect your car to last 25 years. Today most people never wax, never wash the car, never re-paint, are lucky to do an oil-change yearly, and expect their cars to last 200,000 miles. Dealers haven't helped by charging $300 or more for a 10,000 mile service, $750 for a 15,000 mile!

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