Source of pesky leak - PeachParts Mercedes-Benz Forum

tbomachines · #1 06-24-2009, 01:31 PM

With all this rain we've been getting in the Northeast lately I'm at my wits end with tracking down a leak. I knew that my rear window seal was bad when I got the car, so I ordered a new one. When I discovered a big spot of hidden rot in the trunk I said "screw it" and decided just to goop the window instead of risking breakage trying to replace the seal using the clothesline method. I sealed all around the seams with 3M windshield sealant, patching up any remaining possible holes with weatherstrip/rubber adhesive (which btw is awesome stuff!). It fixed all of the leaks around the window, or so I thought.

I sprayed the area excessively with a hose and found one more leak, which I patched up. For good measure, I sprayed the whole area with rubberized undercoating, hopefully getting any miniscule holes I might have missed. So yesterday I was happily cruising along in a lovely drizzle/sprinkle and I noticed that there was water leaking into the bottom of the back seat. With the seats out I found that it was entering somewhere behind the drivers side rear wheel-well support (where the seatbelt is) and trickling down to the floor. So once again I take out the hose and spray down the area....nothing. Yet it is raining again later and I see it begin to trickle down!!! It is coming above the door, so I don't think it would be the seal. I'm beginning to suspect the sunroof drain?? Does anyone know where/if the sunroof drains? Could it be anything else? I'm pretty confident the rear window is completely sealed, and I didn't see any moisture around the corner or top. And for some reason I remember reading that the sunroof drained to the transmission tunnel

Edit: Car is 1982 300SD. Also, the headliner looks fine and no signs of water damage or sagging.

Jeremy5848 · #2 06-24-2009, 01:36 PM

I don't know if your car has both front and rear sunroof drains. The front drains usually run down the A-pillar to the front wheel well; a rear drain would probably end up in the rear wheel well, which might explain your problem.

There have been many discussions on this forum of various ways to clean out a clogged drain. Some people advocate use of the plastic line that string trimmers use, others like a small drain snake that Harbor Freight sells.

tbomachines · #3 06-24-2009, 01:52 PM

Thank you Jeremy. I will have to check the sunroof drains, I didn't realize there was more than one! I assume I'll have to take the headliner off in order to verify.

All of my search results actually came up with water on the floor pans rather than behind the seat so I was a bit hesitant to post another "leak" thread. I can clearly see it dripping down from behind the pillar. I will have to check the sunroof drains, I didn't realize there was more than one! I assume I'll have to take the headliner off in order to verify

Jeremy5848 · #4 06-24-2009, 05:37 PM

You may not have to remove the headliner. First open the sunroof all the way and look with a very bright flashlight or trouble light to see if you can see anything that looks like a drain hole back there. Next, check EPC for your model-year and see if there are any references to sunroof drains. Seems to me that my 124 has only two, in the front, while my 210 has four. Next, try probing with some thing stiff and flexible, like string-trimmer line. Next, try carefully pouring a small amount of water into the channels at the sides of the sunroof and see where the water goes. You can temporarily stuff something in the front holes and see if the water disappears. If it does, you have rear drains (or bad rust!). You could also look in the trunk near the cable to the sunroof motor; that would be another place where a rear drain might be positioned. Lastly, look under the car to see if you can see where the various drains terminate. They are sometimes hard to recognize. Only after doing all that would I pull the headliner.

Note that the above is because I'm afraid I'd never get the headliner back correctly. Others may have a different opinion. YMMV.

Jeremy

Jeremy5848 · #5 06-24-2009, 05:52 PM

EPC for your model-year shows part number 003 997 63 82 "Hose, sliding roof water drain, order by the meter." It shows in the drawing as being at the rear of the sunroof. Going by the drawing (which I don't trust) there are also front drains but I can't find a part reference. If there is a front drain you should easily find it.

tbomachines · #6 06-24-2009, 06:01 PM

Quote:

Originally Posted by Jeremy5848

EPC for your model-year shows part number 003 997 63 82 "Hose, sliding roof water drain, order by the meter." It shows in the drawing as being at the rear of the sunroof. Going by the drawing (which I don't trust) there are also front drains but I can't find a part reference. If there is a front drain you should easily find it.

Thank you for checking that! I am going out tonight and seeing what is up there. It wouldn't surprise me to find a rust problem judging by the rest of the car...it was sitting for quite a while.

Jeremy5848 · #7 06-24-2009, 09:30 PM

Also . . . EPC shows

1985 300D (W123, OM617) part number 003 997 63 82, Sliding Roof Water Drain, "order by the meter" and it lists "Hose, front" and Hose, rear" so there are four drains, I thought only two.

1987 300D (W124, OM603) part number 124 782 01 96 Hose, replaced by 124 782 07 96, "Water drain, front, 1100 mm, qty 2" and "Water drain, rear, 1470 mm, qty 2." So it has front and rear drains also and I could have sworn when I cleaned it a few months ago that there were front drains only.

1996 E300D (W210, OM606) part number 210 782 01 96 Hose, replaced by 124 782 07 96, "Hose, water drain, qty 4."

Three E-class examples, four drains. I'd look for rear drains in your S-class too.

Jeremy

tbomachines · #8 06-25-2009, 01:03 AM

I cleared out the sunroof drains today and they were fine. I sprayed water on the sunroof and it came dripping out of the wheel wells, where I assume the drains are. So I decide to douse the car in water and see what happens....the trickle appears.
I gave up. I put in a little trash-bag funnel the highest I could find it and put that through a tube into a bottle in the trunk. As long as I don't forget to empty the bottle I should be ok for a while. Rust doesn't concern me anymore since I'm looking for a nice-bodied w126 to drop my OM617 into. I do appreciate the effort and information Jeremy!!

whunter · #9 04-10-2011, 10:25 AM

Found a good sunroof drain cleaner
http://www.peachparts.com/shopforum/diesel-discussion/207158-found-good-sunroof-drain-cleaner-post1757958.html

.

tbomachines · #10 04-10-2011, 01:57 PM

Thanks Whunter! I am surprised that the snake fits in the sunroof drains. I found that a weedwhacker string works very well since it is stiff enough, strong yet flexible. It also won't break any rubber seals since it is just plastic and blunt.
An update on my situation that prompted this thread (I was surprised to see this one brought up again!) - the source of the leak was the rear window seal. Unfortunately it had rotted out a good portion of metal behind the seal (couldn't see it) and it just exasperated the leak. I had to junk the car because the rust was so bad, but the engine/trans is now in another 300SD which I drive daily.