Water Intrusion Perplexity

[shertex]

So on my 91 300D I discovered that the front passenger floor and rear right carpet were soaked. Removed the front "floor" (the piece with the foam rubber).

Sent to my mechanic and asked him to confirm drains were clear and to diagnose issue.

He said drains are clear and the area the looked suspicious to him was the area above the rear windshield: when water was sprayed on it would disappear through top...it looks as though gasket is missing. But he said there was not much more he could do without removing panels, etc...

So to test the rear window hypothesis, I taped it off and waited for it to rain.

With the car slightly nose down parked on the street and a steady rain falling, I noticed the following: water is coming up through cracks in the floor. So I'm thinking maybe water is entering through the engine compartment and there's some sort of breach in the firewall.

But then, later that same day, now with the car parked in the driveway and no longer nose down, we had this horrifically torrential rain. I was certain that the footwell area would be soaked. Instead, it was bone dry. The only difference in the two scenarios is a slight difference in the angle of the car.

So now I'm suspecting that the intrusion must be in the rear....to account for what I've observed.

Grateful for any insights as to how further to investigate.

[87tdwagen]

Were the sunroof drains (if equipped) the ones checked? If so, I would still recommend removing the passenger footwell kick panel, should be just a screw or 2 and unclipping from the sheet metal. There you can see in the A pillar where the drain line connects to a rubber elbow that exits exterior of the body behind the front fender. Often times, due to age, this elbow can crack and whilst the drain and line may be clear, the water leaks inside the A pillar and onto the floor. You can stuff the area with paper towels and next rain or hose check see if they remain dry.

The rubber part is NLA, but a suitable rubber hose end can be cut and shoved through the opening to the fender exit and coupled with the drain line.

Presumably to test the rear window leak theory, you could angle the car nose up and see if there is an issue with and without your tape cover. I would imagine that the parcel tray would show signs of wetness up top or below in the trunk from a rear window seal leak.

good luck

[jdulle]

You could also check the bottom of the rear wheel well. This is an area which leaks on mine, especially when driving. there is a place at the bottom that rusts out and there is also a body plug higher up that rusts around the perimeter. I would say the body plug is too high up to leak when parked. You could also remove the fender to check that area. There is a spot behind the fender close to the door that rusts out and can leak.

[Sugar Bear]

I recognize that the drains have been checked; but, my W124 had these symptoms and the problem was water retention in the rocker panel. The water stayed in the rocker until it got high enough that it backed up into the RF floor.

Find the 3? 1.5" round black plastic plugs along the rocker and remove them. On mine it was plugged drains but not the obvious e.g., sunroof ones instead it was the rocker panel drains.

[Junkman]

Start with a hose at the bottom of the back glass and slowly work your way up. It helps to have the carpet and perhaps rear seat removed. Rust under the rear glass gasket can go into thr trunk and sometimes the passenger compartment.

The door seals can leak. The only way to find is to decide to be thorough. I always try to short cut then take it all apart when the short cut doesn't work.

[shertex]

For now, taking the poor/lazy man's approach...bought a car cover!