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I have a VW passat with a 100k miles that is heading towards the junker because of an idiotic water leak in the passenger side.

The TCM (transcomp) under the passenger seat in the cabin has been corroded from insidious water getting in despite spending nearly 1000$ to fix it.

Can I replace the TCM? Will a mechanic fix the leak? 1 mechanic emptied the water and drilled two weep holes. Another mechanic cleared the gutters in the engine. Water is still there.

What year?

You need new mechanics.
Yes, a tranny control module can be replaced and the reprogramming protocol initiated.
But I would not trust it to a guy who drills drainholes in the floor or a guy who clears the “gutters in the engine” (whatever that means).

The leak can be fixed. It’s probably coming from the heater core, or perhaps plugged moonroof drains (if you have one). It may even be a rothole path from the wheelwell, although if that’s the case the car is probably shot anyway. Finding the source of leaks can be tricky, but it isn’t rocket science. Of course, the guy who drilled the drainholes clearly isnn;t a rocket scientist anyway…

Volkswagen Passat

Model-Year ?

Some problems are Make, Model and Model-Year specific. Without all these 3 pieces of information the information that you receive could be limited.


Model-Year Specific Problem Example:
According To Volkswagen, Some 2001 - 2004 Vaolkswagen Passats Have Developed Water Leaks That Cause A Wet Floor In The Passenger Footwell Area, Usually Following A Heavy Rain.

The water enters the vehicle through the seal on the cabin air filter. The water leak is caused by either a faulty seal and/or debris blocking the plenum drain.

Replace the seal if necessary and check and clean the drain (under battery) and the area near the drain.

I can imagine that if the water got deep enough that it could back-up under the seat. Also, depending where the car is parked, an incline could exacerbate the problem.


Well, you got to fix the water leakage problem first. Sometimes it is possible to repair these modules, which is usually less expensive than a new one. Google “Auto module repair”, there should be some links there. One I’ve heard of (but never used) is called Module Master I think.

If this is a common problem, it might be worth relocating the “transcomp” or taking measures to protect it from water intrusion. If the module doesn’t need ventilation, you might be able to use silicone sealer on everything, or simply mount it up and away from the water leak, assuming you don’t have to modify the wiring harness too much.

Skilled mechanics diagnose and fix, idiots that know how to turn a wrench throw parts at a problem. The same could be said for any skilled trade or profession—a skilled locksmith will open your door without breaking anything, a butcher will use a crowbar or drill. You can take your PC to a professional to have a virus removed or a problem solved, or you can go to “Geek Squad” or similar where they will wipe the hard drive and start over.

Sorry VW Passat 2000 1.8L turbo automatic 104km

It is really hard to know what is going to happen until after the fact. I guess I must have a tattoo on the back of my head that reads backwards “REKCUS”

Thanks for a lot of great advice but I still need to find a good mechanic. I had cleared the drains under the battery when I saw water welling up there… It is possibly rot from the wheelwell as that area is corroded… I’m thinking I might just rip up the carpet, dry it, baste the area with silicone and strap the TCM as my front passenger.

I forgot to mention that the last mechanic I went to kindly offered to junk the car for free instead of charging me 300$ for a flange.

How old is this car? Is the body in good shape? What about the paint job? What about rust? Is there a lot of rust? What about the routine maintenace? Has that all been kept up to date? If some of these items are “iffy” or just plain “bad”, your mechanic may be right that it’s time to move on. It’s a shame w/just 100K on the engine, but if the body integrity is shot, sometimes the best way to solve the problem is a new car.