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740 Where the heck is my water leak coming from?

Bones

Bones

New member
Joined
May 28, 2008
Location
New Orleans, LA
So, I've stripped out my interior, in the middle of cleaning everything- but I still cant find the source of my water leak. It's in the back passenger seat, there's a nice pool on the ground as you can see, and before I sopped it up, a small pool on the hump for the backseat as well (rained last night, car has been sitting stripped for a week now)



Things I've checked:

Cleaned cowl and drains, draining well, no leaves blocking any of that
Black panel near passenger kick panel is sealed
No sunroof
Door seals look ok, dunno though
Yellow plastic plugs seem ok

Anyone have any ideas? It's horrible and driving me crazy. I've run tons of water over the car, with myself inside and outside, can't tell anything.
 
Does't the windshield drain into the cowl? If it was leaking, where would it trickle water from? The foam and carpers where the passenger's feet would be are dry at the top (near the blower motor) but wet on the floot, presumably from the water leak in the back flooding up front.
 
Yea, I guess if water is getting on the back seat itself and on the floor, it must be the door seal. If it was the door, water would be sloshing around. The seal looks good-I dont get it. Sigh.
 
My 740 has the same problem, I am interested to see what you find.
Have you tried the powder trick to see which direction the water is coming from. Sprinkle powder around to see water trail.
 
Ehh i'm going through this as well. I plan to leave my floor carpet out so I just drilled a hole at the lowest point where the water sits. It drains out. Good enough for me.
 
If you can narrow it down to the most likely place, just run a hose on it and then check for leaks. That's how they do it at Bergeron anyway...if you need a hand text me. I'll be uptown on Friday.
 
Well, a little update- as volvotech knows, it rained like crazy all day today- but I put a tent / carport thing that only covered the front and rear doors, not the cowl or the trunk. No water got in the car at all. So, I'm guessing it's the rear passenger door seal. Looks ok, but I spose I'll pull a good looking one at the junkyard and hope that works.

Anything I should know about changing out the door seal? Hopefully so it won't leak again.

And yea, I'll be working on the car all day fri, sat, and sunday- I finally got all my parts in, and it's just a matter of getting it all on there. If anyone wants to come over and hang be my guest :)
 
Try this.

Hi. I'll tell you exactly what the problem is. There are two drains in the trunk, in the wheel well areas. They have flapper valves in them, I cant remember the exact layout of how they appear, but if you look in there you will find them easily. These drains get clogged up with debris over time, and then overflow at the top, and the water spills into the rear floor area. I had a customer's 740 with a bad case of this once, and it was hard to find. Once I did, and cleared the drains, no further problems. Check it out.
 
Oooo, that does sound exactly what the problem is- there's condensation on the inside of the trunk lid, the trunk carpet was damp, there was water on top of the passenger seat hump, and on the floor. I can't wait to go home and check it out!
 
Bones said:
Oooo, that does sound exactly what the problem is- there's condensation on the inside of the trunk lid, the trunk carpet was damp, there was water on top of the passenger seat hump, and on the floor. I can't wait to go home and check it out!
Click to expand...

The reason it's so difficult to nail down is, the drains are likely draining out slowly, so therefore when you run water across it, it takes a good while until they fill up and run over into the car. I almost never found it on the 740 I mentioned. Good luck.
 
Alright guys, found the leak.

So, if you have a car with wet trunk carpets, wet headrest area, wet backseats, wet back floors and front floors....

It's your rear windshield. After taking a look at the trunk drains (which were not clogged, but I siliconed the clear plastic plugs in to keep water from seeping out), I saw that the hump that the ski hole is cut out of was wet, and that the backseat / floor was wet......then I pulled the headrest carpet and saw it was moldy on one side......so I ran water over the rear glass......looks like it is seeping out of the seal, down into the trunk, down the hump onto the seat, down to the floor, and finally filling up to the front seat floor.

Guess I'll be getting the glass resealed when the car is actually running. Now to clean the entire interior, throw all the carpets and seat covers into the biggest washing machine I can find, and maybe run an ozone generator to kill the damp smell.

So check your rear glass seal!
 
Have an 86 wagon with same problem on rear passenger side, so probably not the rear window (it is parked on a uphill slope, so any tailgate leaks would drain back, and there is no water on or under the seat area). Spent a lot of time with the sunroof, finally took headliner out and there is no evidence of water leaking there. The seals on the wiring in the doors look OK too.

I can think of two possibilities, either something is getting in in the front and running under the rubber foam to the back (no puddles in the front passenger seat), or it is the rear door seal which does seem a bit hard.

What do you use to make a new one? I don't know what that rubber material is called. Figure it is mostly pointless to try to find used as it will likely be equivalently hard or soon so.
That is assuming I'm moving in the right direction here with rear door seal.
 
As a suggestion, purchase some silicone grease (dielectric grease will do) and apply a thin coating to the contact surface of the door gasket. Close and open the door a couple of times and then check the grease line on the sheet metal where the gasket contacts the sheet metal. A nice evenly spaced grease line all around the door suggests good gasket contact which means that is likely not the source of the leak. No contact areas or areas where the grease line is thin are sources of potential water ingress.

I had a 1987 745 turbo with interior moisture problems; but, they were caused by a failed heater core which very slowly leaked coolant into the driver side footwell. A fine sticky mess to clean up.
 
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