Need help with leak from behind dash...190e 16v
 

Hi all:
The alarm in my car started going off randomly so I pulled the passenger side carpet to unhook the factory alarm. I noticed that the passenger side floor board was wet. It looked like something was leaking from behind the dash, since the rubber pad under the glovebox and the dash on the passenger side was damp and cracking from too much moisture.

Could this be a heater core leak? If not, what could it be? I had my windshield replaced a while ago by professionals so I doubt it is that. Any help is greatly appreciated.

leak
 

my money is on the windshield,have it checked.

If it was a heater core leak, you would smell coolant. Turn the heater to max hot with fan on low and see if you notice any steam or coolant smell. Also, how is your coolant level?

I bet if you soak up some of this moisture with a white paper towel, aside from dirt you will find that it is just plain old water, probably from a windshield leak. You did state that the windshield was disturbed a while ago?

Occam's Razor

The windshield was replaced by safelite, but I have never noticed this problem before. If it were the heater core that is leaking, where does coolant usually accumulate?

If it is a coolant leak, it could be anywhere. Heater core, which is in the center console area behind the stereo. Possibly a line to/from the heater core. But again, I would verify that you are losing coolant. If you're not, then it can't be coolant.

leak
 

they disturbed the windshield and it leaks.

Potentially a leak from the evaporator?
 

I don't know how the drainage is on the W201, but I have had the problem on a Ford (strike me down for comparing the two, but, hey, it comes down to the same physics (Physik)). The drainage tube for condensate leaked at the firewall behind the carpet, creating a big puddle on the sheet metal, which then rusted. Cured by a liberal application of silicone caulk/adhesive.

Again, he needs to tell us if he is losing coolant (he has said nothing on this matter). If he is not losing coolant, there is no way it is coolant that is leaking in.

As for the condensate drain, that is a possibility as well, though not likely due to the height of the glove box pad which he said was wet (it's unlikely that water could leak upwards). Which is why I suggested soaking up some moisture with a white paper towel. Clear water will eliminate the possibility of coolant leak.

Check out the link I posted on Occam's Razor, a very basic scientific principle that states that, all things being equal, the simplest explanation is the most likely. He told us the windshield had been disturbed in the past yet somehow he is ruling this out, as if the installers are not capable of making a mistake, or as if the materials used in the installation cannot break down.

I'm not saying it is definitely the windshield, but logic would dictate that he should check that first, then move on to the more complicated things. I will be watching this thread as I'm interested in finding out exactly where it is actually leaking...

I didn't rule it out, but I consider it unlikely because my windshield was replaced twice due to cracks. The first time the installer did a lousy job, and the second time the installer was so disgusted with the work of the first guy that he made sure to put a lot of sealant around the windshield. The water was in fact dirty but didn't look like coolant...although it did have a faint odor. I'll take it to the windshield place...is there any way they can check this without removing the whole windshield?

I'm a real dummy when it comes to testing windshield leaks. A/C leaks, heater leaks, oil leaks, no problem because I just use UV dye. But the prospect of dilution due to the large amount of water likely needed to trace down a windshield leak leaves me baffled. Not to mention if it did make it into the cabin, it might stain the carpet or fabric. I would just suggest doing a search here or maybe one of the experts can chime in.