I have read and read and read the posts on the forum for info on this, but I have not encountered anything quite as un-diagnosable as this. Here's my situation:

-For a while, water has been pooling up in the backseat passenger floor of my 300cdt. Common symptom, right? I figured it was the window seals--the easy fix-- and went for that. No results. (I read in some post someone said it takes a few days for the rubber to conform to the window, but I don't think I'm lucky enough that it's that, although I just had them replaced 6 or so days ago).

-This failing, I tested further by putting a hose on the passenger side of my front windshield and observing where the water entered up in the front footwell. It was coming through in the seam where the bottom of the floor (the floor being a plastic hardcoat covering that flaky stuff I guess for sound-deadening and then the steel plate underneath) meets the right side panel of the footwell (as you're sitting in it).

It seemed straightforward enough, so I sealed the area with silicone sealant. I also sealed the hood pocket area behind the drain spots preventatively since it had a little rust (hopefully not a bad idea, but probably was since it sealed rust in ). I was in a water-stopping frenzy.

-Now when I test with the hose prior to these repairs, water still comes in, but instead of coming through the crack before, it comes through various other cracks in the plastic hardcoat in the bottom of the footwell like little f*#$ing springs.
This means that water must be somehow entering the space between the firewall and the plastic hardcoat, quickly soaking through and past the black sound-deadening stuff, and then welling up wherever it can find a place to get out.

Sure I could just seal all the cracks, but that would be a kind of retarded way to do it since there would then just be water sitting on the metal panel beneath, rusting it out.

The only solution I can think of is to crack the plastic hardcoat open all over the passenger footwell, scrape out the sound-deadening stuff, and search all over the metal panel for a hole where it is coming in. I'm afraid though that if I do that I won't find one and will have destroyed the footwell for nothing.

Could it be the seals have not adjusted yet? How could water be coming in this mysterious in-between space? Furthermore, how could rainwater, simulated or otherwise, even find its way in there? My suspicion is that it's coming through the area around or behind the hood pocket, although I sealed that.....

Please help me on this, I can post pictures later if needed. I'm on my last nerve with this water deal. I can take all the mechanical repairs associated with a 21 year-old car, but fixing rust and searching fruitlessly for a stupid little leak is infuriating. I was so happy thinking I had fixed this problem, and now I feel like getting a crap asian import just out of sheer desperation.

Run some searches for body drains or water leaks. Water must follow drain channels through the body and exit out the drains in the bottom of the body. The drains look like rubber nipples if you look under the sides of the car. Check the manual at skinnerbox. I bet this is also mentioned in the FAQ sticky threads in this forum. If your body is already rusted out this may not help you.

http://www.peachparts.com/shopforum/search.php

I have cleared out the hood pocket drains many times, I know the problem is not there.

I did find a drain spot at the bottom of the doors on both sides, and discovered where all the leaves had gone in the North Central Florida area for the last 21 years. Never has a clotheshanger been so useful. However, this brought no change.

It can't be rust in the hood hinge pocket, it is sealed and good to go.

The funny thing is this: when the water pours down the area just below the bottom left corner of the windshield (as you look at it from the front), this is where it enters the foot well/sound-deadening stuff. How could this be? I thought that area just went right into the hood hinge pocket, so how is it getting in? It must be my seals, right?

I am perplexed and the summer is approaching, in which no car cover can save me.

It sounds like you are taking a good approach. Start low with the water hose and work your way up. Use tape or whatever you can to isolate different areas and keep the water right where you want it to eliminate the different possibilities. Be patient, take your time and remember that water flows downhill.

Did you replace your windshield seal or side window seals?

The sunroof has drains that go through the body.

Silicone is not good to use on auto body work. It will promote rust and make it difficult to get anything else to stick.

83 mercedes, have you checked under the battery and tray? Just trying to help. steve 83sd

This is a good question, and it has already been answered. Here is a link to another recent thread in which 83mercedes describes problems with the area under the battery and tray.
Wheel Well Gone!!!

Could very well be that these two threads are about the same problem.

Does the drain under the battery actually drain? Just because it's clear on top desn't mean the whole drain pipe is clear. Make sure it's draining rapidly otherwise water is still pooling up under there. Also, IIRC there are actually two drains. One is directly below the battery and another is up a bit higher, closer to the fender. The whole area under the battery should drain rapidly when you flood it. I wouldn't waste your time plugging the areas in the footwell that are leaking, the water will just find another place to leak out. I agree with the others that you are on the right track using the hose to find where the water is entering.

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1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold

IT WILL RUST OUT UNDER the windshield seal and that will allow the water in which then runs down the fire wall and under your black seal.
john m

The second drain under the hood pocket one is also clear (besides, it has the rusted out area to drain through ).

The sun roof may be contributing to the problem, but that's not where the majority of it is coming from.

I have replaced both the side sqeegee type seals that slick the water off the window as you roll it down and the front and back windshield seals, to no avail.

Someone mentioned that the area under the windshield seals rusts out and allows water in. Should I take it back to the shop or ask them about it? I'd like to think it was a problem with the seals...

There has to be a big compromise, because the other day it rained really hard, so I put my car cover on and a puddle still accumulated despite the cover from only about 24 hours of heavy rain.

Look at post #175. - #181 and #186. - #190.
Who has the most rust and still drives
Water Always Wins, if the leaks are not stopped.

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