Mystery water leak

[BavHyena]

Hello all,
So during a brief lull in the rain here in California, I took a look inside my '74 E3. Lo and behold, the rear footwells were full of water. Right side had standing water, left side is merely very wet. The front is dry. The headliner is dry. The seats are dry. Rear parcel shelf is dry. Door seals look ok. No sunroof. Slight dampness in the vertical carpeting under the rear seats. I can't tell if that's just wicked up from the footwell or not. Any ideas where the water could have come from? Is there a known water path from the trunk perhaps?

 

[Stevehose]

I am not sure if E3’s have the same rocker drain holes but this thread may help:

Check your rocker panel drain holes!

Hear me now and believe me later, if you haven't physically cleaned out the 5 drain holes on each rocker, do yourself a favor and pull off the covers asap and run a zip tie or metal wire up each one to verify they are clean. I confirmed the reason why my driver side carpets got soaked on the...

e9coupe.com

 

[dang]

I'm assuming the car was parked the entire time? If the car was not on an incline my guess would be the rear window seal. They usually leak around the top corners where it shrinks and pulls away from the frame.

 

[HB Chris]

In an e39 it comes from rear door vapor barriers being unglued or missing. Strange but true.

 

[rsporsche]

my thought was also a rear window seal. water getting in at the top and traveling down the vertical portions of the rear seal ... then because of the angle transferring to the interior ... then down behind the rear seats where it will end up on the floor. this wouldn't get the parcel shelf wet, but underneath it may be damp.

 

[Christoph]

@Stevehose very likely is right. The E3 sills have five drain holes on each side that tend to get blocked. Usually the sills are full of wax, the suns shines on the car, then the wax moves downward. Repeat for some time, and you get blocked holes. In the end the water finds its way inside through the holes on the inner side of the sills. Opening the drainage is easy, just use a small knife or screwdriver. Had that problem myself in summer 2010 after the usual torrential thunderstorm at the Nürburgring. Passenger side flooded several about 2 in. high, driver side completely dry. It took weeks to understand, well, it took me weeks. Did it last in September on a friend's car in public. Some very surprised spectators when the water was flushing out.
This only applies if you parked your car nose upwards. If not, @HB Chris 's hint might help. You might check the drain holes in the rear doors and, if necessary, remove the door cards and fix the foil that is glued to the inside of the doors.

 

[dang]

Maybe I'm picturing things wrong but it seems like water getting into a door would either stay in the door or drain down onto the door threshold and away from the inside of the car. Wouldn't the water have to get past a seal, either on the door or the rear windshield? In other words, you can have no seal against the outside of a door window and run a hose on it and no water would get into the car, just the door. No?

 

[rsporsche]

the door scenario could come into play if the door drains were clogged and enough water was trapped to spill over the metal at the bottom that holds the door card - going between the door and the door card ... which would be inside of the seals. but that is a lot of water, and there would still be some in the door bottom. however, the same argument about the rear window seal could apply to the rear side window seals - water could get around the vertical seal and travel down and get between the door card and door ... ending up on the floor.

the most likely could be the rockers ... and then the rear window or side window seals. all of this presumes that the rear 'c' pillar vents are properly in tact.

 

[bavbob]

The inside of the doors are angled outward and toward the drains. I found the sound deadening material used at the factory which was just a single square panel, actually retracted , separated from the door and sitting in a pile at the bottom of the door. Clogging the holes and no sound deadening.

 

[dang]

Well speaking from lots of experience, I've had way more issues with front and rear window seals than anything else. For cars that are sitting/stored. That's were I'd start, and we're about to get another week of rain so it will be tested!

 

[HB Chris]

The e39 is a classic example of wet floors, it’s all over the BMW forums. The membrane becomes loose and not glued at the bottom. When glass is up water runs down the inside of the inner panel, all of this is inside of the door seal Itself.

 

[rsporsche]

i wonder if its because the e39 door has more vertical curve - the e3 door is more 'slab' like. but i get what you are talking about - architects always have fun trying to track down water leaks on roofing. where you see the water is rarely where it is coming thru the roof.

 

[HB Chris]

i wonder if its because the e39 door has more vertical curve - the e3 door is more 'slab' like. but i get what you are talking about - architects always have fun trying to track down water leaks on roofing. where you see the water is rarely where it is coming thru the roof.

Inner panel is vertical.

 

[Krzysztof]

I had such a problem in other car than BMW in the past and the root cause was ... trunk seal.
Quite often also the taillight seal can be the reason in many different brands.
Rear door-sourced leak is also popular.
Last year I have had a leak in front foot well. The root cause was the panel of protection foam (sound isolation) originally glued by the buthyl rubber. Even small discontinuity or minimal gap between the inner door structure and the foam was causing water appearing around driver's foots. Really nasty to nail it down.

Not sure if the water can get into the rear foot wells as there is a steel panel between the trunk and the rear seats but maybe it would be good to check the trunk for any water residue.

Just an idea

 

[Christoph]

Assuming the water came in through the rear screen seal then it most likely ran down behind the backrest of the rear bench. If so the three felt stripes on the panel behind the backrest must be soaking wet. Lifting the backrest a bit and putting a hand behind it should confirm this possibility or rule it out. Plausible or not?

Vapour barrier foil again. Some time ago I had to open the driver's door, to my surprise I wasn't the first. Some untutored mechanics had been there before when the glue under the foil was still fresh. To remove the foil they must have used a hot-air fan which caused the foil to shrink. Instead of replacing it they just taped the remains diagonally across the door leaving the foremost holes open. Though that footwell always remained dry there were clear signs of liquid splashing against the doorcard.