Water in Trunk, Tail light failure on OBC

[Ubertino]

So I've been reading the other threads for a while now. On my '95 M3 I get a tail light failure on the OBC, but only when I turn on the headlights. I've got water in the trunk, but everything I've read says that the bad seals and such lead to complete failure. Even when the computer says failure, the lights work just groovy, everything normal. I'm going to replace whatever gasket and whatnot, but I'm worried that there might be something else going on?

Thoughts would be appreciated

[thejlevie]

The tail light warning problem could be as a result of corrosion on the bulb holders or in the sockets in the taillight housings. This is something that you want to deal with soonest. A poor connection from corroded contacts will cause heating, which will accellerate the corrosion, which will lead to more heating and more corrosion. At some point the service temperature of the plastic will be exceeded and the taillights ruined. Been there, done that!

Obviously you want to fix the seal problem. The obvious place to look is the trunk seal, but leaks at the taillight seals are also a possibilty as are rust thoughs around the tire well in older cars. But the first order of business is to pull the bulb holders and check them and the sockets for corrosion. Clean any corrosion found and use one of the conductive moisture/air barrier greases (Alnox, etc) to retard further corrosion. If there's a good bit of corrosion on the bulb holders get new ones (much cheaper than a taillight).

[Ubertino]

Rock. Thanks- although the entire trunk area has been rebuilt after a college student hit my non-moving car. So I know there are no holes or anything. I'll check those seals and bulbs.

Thanks!

[thejlevie]

I've seen something like three cars that had problems with the seal behind the taillight housings after repair from a rear ender. The shape of the rear can look fine after the repair, but the sealing surface may still be distorted enough to allow a water leak. And in time that will cause the problem you have.

You can check seals for correct contact by chalking the rubber and looking to see if there's a uniform chalk line placed on the sealing surface. Baby powder or powdered chalk is also useful in a search for for the source of a leak. With the carpeting and such out dusting the body surfaces with powder will reveal water tracks the first time it leaks.