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The fear of flooded cars

Most people would advice you to dispose your car if it got flooded. I am here to tell you otherwise - there are things that you can pay attention to that can resurrect your beloved car and be operational, without any issues.

My Corolla got flooded 5 years ago during the Memorial Day floods in Houston, TX. The engine and transmission didn’t get flooded, but, water got inside the cabin.

It was my first experience of my car getting flooded. I didn’t know what to do. I was relieved when water didn’t enter the air filter, battery, engine or transmission. If you pull the dipstick and see water beading on it, water got in the engine. It is obvious to see if water got in the air filter too - it will be damp. If either of these are true, Do Not attempt to start the car.

Even though there was no obvious beading on the dipstick, I didn’t want to take a chance with starting the car. If even a tiny amount of water enters the engine, water being less compressible than gasoline, will put tremendous amount of force on the pistons, causing it to bend during the power stroke. To remove any water in the pistons, I removed all the spark plugs and cranked the engine. The car won’t turn over, but the pressure from cranking will spit out any water. You’ll have to repeat it several times and keep wiping off any water from the spark plug holes with a cloth tied to a stick. Once everything is clean, reinstall the spark plugs.

At this point, I became over confident that my car is going to be ok, since there was no water in the engine. I turned on the ignition and the car started up. My sigh of relief soon turned in to despair when the dashboard was lit with several warning lights, as if it was Christmas in May. The check engine light and SRS lights were the ones that got me worried the most. There wasn’t anything seemingly wrong with the car expect for these lights and a louder sound from the pulleys. The car was operational, though. There are no issues with loss of power or driveability.

I knew that there must be still something wrong due to this flooding. So, I disconnected the battery, removed the car seats and carpets. Had them shampooed and disinfected thoroughly. I let the car sit in the Houston summer for a good 2 months, occasionally leaving the car open for the moisture to escape. This was done to let any water that got in the wiring to dry off. Little did I know that the damage was already done due to the battery being connected to the electronics while it flooded.

Lesson learned was to remove the battery if you know that water is rising fast around your car and you cannot drive it away to a higher elevation. Better yet, get 2 sets of ramps and keep at least the engine bay elevated or, even the whole car.

Once the car was bone dry, I reinstalled the carpet, seats and the battery. I was hoping that the CEL and SRS lights would disappear. But, my heart sank when they stayed on. There was one more thing that I did before taking the car to the mechanic. I raised the car on jackstands and got under the car and removed all the twigs and leaves that the flood brought in which got stuck in the exhaust and around catalytic converter. Many people overlook this and these leaves will catch on fire when the engine is hot, which is most likely why some flooded cars catch on fire while been driven. You’ll have to thoroughly clean the underbelly of the car for anything that can catch fire.

One mistake that I made was not to leave the doors open everyday or remove excess moisture from the rear windshield. This caused bubbles to be formed under the sunshade film on the rear windshield. It was an issue that could be solved easily at that time with an old credit card. if I knew better.

At the mechanic’s, I was told that the PCM (main computer of the car) was fried. They got me a new aftermarket unit and programmed it for me. Even with an aftermarket PCM, it cost me around $1500. With the new PCM, the CEL is gone, but the SRS light stayed on.

Lesson learned was that, during a flood, power must be cut off from the PCM before water gets in. Turn on the head lights to drain any left over charge in the system. The PCM on most Corollas can be found under the glovebox. It can easily be removed with a wrench set. Carefully remove all screws from the PCM (this will void warranty). Warranty will not be an issue if your car is a few years old. Remove the electronics board and wash it under a faucet with warm water. Use some liquid soap and a soft bristle brush to clean it thoroughly. Most people will cringe at the thought of washing electronics.

These electronic board can be washed as long as there is no power source attached and all capacitors allowed to completely discharge. Dry off the board very well using a low pressured air pump, blowing off water from under the IC chips and every component on the board. For a good measure, let it dry for couple of days before putting it back.

Doing this PCM cleaning would have saved me $1500 and my car would still have the OEM PCM. I successfully did this on another car during the Harvey floods couple of years later and the PCM was saved on that car!!

I would use the car with no major issues other than a loud pulley and the lit SRS light on the dashboard. Most mechanics would advice you to take the car to the dealership since they don’t have the equipment to diagnose it. When I took the car to a Toyota dealer, they told me that their equipment cannot communicate with the main SRS module. It will cost around $2500-$4000 just to see what else needs to be changed. I wished a blessed day to those gentlemen and left the dealership with a very sad heart. There is no way that I am spending $4000 for a “Hail Mary” diagnosis.

I knew that if the SRS light needs to be fixed, I have to do it on my own. Many people, including many on this forum also advised me to put a piece of black electrical tape over the SRS light, if it was a bother. Me, being the stubborn goat that I am, decided to fix it no matter what.

The SRS light could be on for a number of reasons - the worst (and most expensive) is a defective SRS module, then it could be the weight sensors under the seat, and lastly, it could be due to corroded wires.

I removed the SRS module from the car. It’s not too difficult to remove. The center console needs to be removed to access it on a Corolla. I opened it up and examined it for signs of corrosion. There was some corrosion on the external pins, but the board was clean. It was a huge relief for me to know that the SRS module is not fried. I cleaned out the corrosion from the external male pins using 100% Deoxit (comes in a small bottle with a long neck). The female wiring harness was most difficult to clean. At this point, a friend of mine used a special code reader to read off codes off the SRS module. The light didn’t go away, but the equipment was able to communicate with the SRS module. I also started seeing the seat belt warning light turn on or off. I knew that, I was going in the right direction with this troubleshooting.

Next suspect was the weight sensor. It is a small black box found under the passenger seat. It can be removed without any tools. When I opened it up, I can see that most components were completely corroded. Luckily, I found an oem replacement on ebay for $30. It was plug and play to install the replacement. Always remove the battery connection and let it sit for at least half hour before attempting any electrical fix around the SRS system (including weight sensor) or the PCM.

With the replacement weight sensor, when I turned the key on, for the first time in almost 4 years, the SRS warning light turned off. It was a huge sigh of relief. I was able to fix a $4000 problem for $30!! At this point, I knew that all hope is not lost for this trusty Corolla. I got a new tensioner pulley too and the loud sound was gone too!!

But, everything wasn’t “they lived peacefully everafter”. Mysteriously, the CEL came on often, each time with a different code. I knew that either the PCM is bad or there must be something wrong with the electrical wiring. I started with the cheaper, but complicated fix - diagnosing the wiring. I removed the carpets, examined every connection looking for corrosion. Whereever I found corrosion, I used a wire brush and Deoxit DL100 to soak and clean it. Sometimes, I had to soak it for a day, clean it and repeat again. Some wires were difficult to follow since they were tucked away far under the dashboard.

I was pestered by a O2 sensor error code on a sensor that I replaced not too long ago. When I measured the signal voltage at the O2 sensor and at the main wiring harness near the PCM, I found a significant drop in voltage. I knew that there is corrosion inside the wiring harness of the PCM. The female pins are too small to clean. After several attempts with Deoxit and a wire brush, the oxidation was gone and the CEL light cleared on it’s own. Now, the Corolla is free of all error lights for over a year. It runs well and gives excellent gas mileage too. It cost me $50 in parts and tons of time figuring what is wrong. Next time, for me or anyone reading this, the hope is that it will save the time figuring out what is wrong.

I am not making a claim that all flooded cars will have exactly same issues that I had. I thought I had the worst (and most expensive) of all problems. Anything else would be minor (assuming that you don’t need a new motor or transmission).

For anyone else out there in a similar pickle, this is my story of how I fixed my flooded Corolla. All the wires are now corrosion-free. They are sealed from further moisture intrusion. The PCM, SRS module and weight sensor are working well too. I believe that there shouldn’t be any further issues. Time will tell if I am right or wrong. Hope this anecdote will help someone else too.

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Come back in 5 or so years and tell us if it’s still working well. :wink:

Frankly if you have full coverage on your car, the smart money is to let the insurance company total it so you don’t have to deal with all the hassle you just wrote, plus sit there for years wondering when the next flood-related thing will break.


Sorry I just couldn’t finish. The issue is water in the electronics that can corrode the wires and parts over time. Not necessarily the engine and transmission although that can be an issue as well as bearings and other parts. Unless you immediately remove the carpet and pad and dry it out you will get mold. I don’t know how you dry seats out unless the foam is replaced. Mold starts in a day or two so two months in the sun just doesn’t do it. At any rate, yeah it may be drive-able but in the long run you don’t want to buy one or keep one if you can help it.

How many hours did it take you to do all this, and how much would you be paid per hour performing work for someone?

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Thanks, interesting story. To summarize, yes a flooded car can often be diy’er rescued, but expect quite a bit of effort to get all the niggles out. Your comment about cleaning the ECM PCB reminds me of pizza-lunch meetings w/ manufacturing engineers. They’d argue about which automatic dish-washing machine brand did the best job of cleaning their newly manufactured PCB’s. New PCBs have a lot of solder-flux on them, and it must be cleaned off. Most of the engineers seemed to agree that the Maytag did the best job. I’m not recommending that folks wash their ECM’s in the dishwasher.Whether a PCB like an ECM is robust enough for that treatment depends on which particular parts and connectors it has, and how it was manufactured.

The actal repairs didn’t take me long; just few hours. The initial cleaning did take a whole weekend. However, I spent a lot of time figuring out what was wrong, especially since I have no intention of throwing parts at it without a proper troubleshooting. The problem was, since most people never bothered to repair a flooded car, for all the common beliefs that are stated in above comments, there wasn’t enough information on the Internet to answer my specific questions. That is why I thought of sharing this story with y’all. It may be beneficial for the next OCD guy like me or a story for the laughs for the rest. Eitherway, it benefits someone.

The car runs well, even with the srs light on. So, I used it as a daily commuter to and back from from my workplace. The time I spent on it is time I would’ve wasted in front of a tv, anyways. I like taking up challenges that others write off as not worth their effort. In that process, I learned a lot and saved one car more from the junkyard. I am sure, that car has a very long life ahead.

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It’s useful information, but you certainly convinced me that I’d never try to repair and keep such a car.

You are right about the corroded electronics and wiring. That is the worst of all problems that can happen to a flooded car, and it happened to my car.

As for drying the seats, the timing was perfect for me. The flooding happened just before summer. I didn’t replace the foam but shampooed and disinfected the seats. Then I left it on our patio, protected from dust and rain for 2 months in Houston summer. The air was hot and dry and it did a good job drying out the seat. No mold would dare to grow in that climate. :smiley:

Ideally, disposing such a car is advisable, but they can be restored too, if one chooses to do so.

While I may not choose the route you took with that car, I enjoyed reading your pursuit to get it going. Nice work. I suspect you’ve learned a bit from it.

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This anecdote was intended only as an interesting story for the laughs (and proof of concept for the daring ones out there), of something that most people might not undertake.

I waited 5 years to tell this story because whatever that would’ve corroded may have corroded by now. It doesn’t take that long for corrosion to play havoc on electronics and electricals, especially if that car is a daily driver. Even I wanted to know how it turns out in 5 years.:smile:

I think you’ll be in for some weird electrical Gremlins in the future. Good luck though.