I think it's safe to say that all production cars have body drain holes that require maintenance. Typically the holes should be cleaned every 6 - 12 months, maybe even more frequently, depending on the amount of detritis that falls on the car. Owner manual maintenance schedules that I have seen specify this cleaning operation and interval.
What happens if you don't clean the drain holes? Flooding as described in this article, or corrosion of body panels such as door skins, fenders, and floor. Carpeting and inner door panels can also be affected. My F-150 often has a swimming pool in the bed (sometimes referred to as a redneck jacuzzi) after a rain storm because the bed drain holes easily clog. Eventually the holes will rust, enlarging the openings so the bed drains more easily.
Rain drainage is not the only source or water problems with cars. A 2000 Mustang I own had a design defect where condensate from the A/C evaporator dripped onto the exhaust pipe near the catalytic converter. This eventually causes the pipe to crack and leak exhaust. Ford's documented fix is to weld up the crack using a particular welding process and materials, which most repair shops would not have. The pipe is stainless steel, so ordinary welding processes cannot be used with any degree of lasting success. A new aftermarket catalytic converter assembly costs about $600.
My windshield gutter is slightly flawed as well. My 2008 Nissan windshield gutter was not installed as one piece and was instead installed as one long piece with two side corners. For some reason the one side corner has fell off so pollen has been collecting there and the rain water flows under the hood. I admit I feel lucky after reading this because I much rather clean out the gutter then have to deal with hot water leaking on my feet.
I have a major aversion to water and vehicles. My 02 Ford F150 has a problem with water leaking through the bottom of the windshield seal and into the power control module effectively shorting out a few of the relays. The only solution is to pull the windshield and reseal. Made by Monkeys
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