W123 Drain Hole Question - PeachParts Mercedes-Benz Forum

jdh122 · #1 07-23-2009, 09:56 AM

After a solid rain I discovered some water in the rear passenger floorboard. I've done a few searches and think that I might have a clogged drain. As I was going over the car trying to identify all of the drain holes and drain exit points, I started wondering if all of the holes on the bottom of my car are supposed to be drain exit points? The thing is, only one of them has one of the rubber covers, and all the others seem to be sealed up with a thin, flexible coating of some kind. I wonder if the PO had some sort of anti-rust coating put on which covered up many of the drain holes? If I push on the material that is currently sealing these holes it feels very flexible, and I believe that I could easily punch through it with my finger. See attached pics for images of what I'm trying to describe.

JohnS · #2 07-23-2009, 10:04 AM

No those plugs are not drains. Most likely this water is coming from up front. You may have a windshield leak or drains in the front of the car that are blocked. Flush out the area beneath the hood hinges. Look under your battery, if there is a rust thru there, that will cause your problem as well.

JimmyL · #3 07-23-2009, 10:14 AM

Your 2 most likely causes of water intrusion on the passenger side, as noted above, are a windshield seal leak and/or a hole rusted through the firewall under the batter tray.
I've had both issues on multiple W123's, and have read more posts about this problem than I can remember.
Sunroof drains and hood hinge pockets are possible, but far far less common.
FYI, any water in the car works its way to the rear floor board.

JEBalles · #4 07-23-2009, 10:40 AM

Those holes are for blowing in that waxy rust-preventative coating.

jdh122 · #5 07-23-2009, 10:50 AM

Thanks. I checked under the battery tray and there is no hole there although the paint is starting to peel and flake. Guess I'll need to do something about that...

I did notice a couple of drops of water on the inside lower portion of the windshield seal after I washed the car a couple of days ago. I sure wouldn't have thought that that little leak would allow so much water into the car. When I was inspecting this leak I noticed that I was able to pull the seal toward me away from the windshield. Is this something that I could take care of with some sealant? The seal itself actually looks fairly new.

Also, one possibly important point is that when it started raining I had the front of the car up on jack stands to replace the engine mounts. When the rain started I closed the hood but left the jack stands in place. After the rain stopped I raised the hood again and the water standing on the hood all at once ran toward the windshield. Perhaps this might account for the amount of water I found in the rear passenger floorboard.

Cr from Texas · #6 07-23-2009, 10:56 AM

IMHO, the elevated front would have changed the drain pattern and could cause your problem. Remove the carpets on the passenger side and test for a leak while level using the garden hose.

jdh122 · #7 07-23-2009, 11:03 AM

Quote:

Originally Posted by Cr from Texas

IMHO, the elevated front would have changed the drain pattern and could cause your problem. Remove the carpets on the passenger side and test for a leak while level using the garden hose.

Well, the car was level when I washed it a couple of days ago and noticed the couple of drops on the lower part of the passenger side of the interior windshield seal. I bet you're right though that having the car elevated could have exacerbated what appears to be a very tiny leak.

Should I be able to pull that inside seal away from the windshield fairly easily, or should it be sealed tight against the glass? I'm guessing the latter. At this point I'm leaning toward purchasing some silicone sealant and trying to seal the area. As I said earlier, the inside seal itself looks quite new.

Is the windshield seal a single piece that encases the windshield, i.e. is the seal I see on the outside of the windshield just the other side of the seal I'm looking at on the inside?

Cr from Texas · #8 07-23-2009, 11:08 AM

The seal is one piece.
I chased a similar leak in my 123 for almost a year. Right hood hinge drain was partially plugged so water overflowed under the battery try and then through a rusted spot to the passenger side under the glove box. Water flowed under the carpet to the rear. Front always seemed dry but rear is the low point. Didn't find the problem until I removed all the carpets and checked with a hose.

tbomachines · #9 07-23-2009, 11:35 AM

I've been chasing leaks in my SD for months now. The rear windshield seal was always the culprit, and I was able to identify where the leaks were (on the inside) so I could put buckets under neath the dripping points. I have a new seal but I ultimately decided it wasn't worth the risk of breaking the rear window and having to pay for a new one (not on a huge budget here). Before, I "sealed" the area with weatherstrip adhesive but it began to flake off. The other day we got over an inch of rain and it filled an entire Cool Hwip container with water in my back seat!! Last night I bought a tube of black RTV and literally filled the entire cavity between the chrome trim and metal of the roof, completely (hopefully) sealing it off. If this is a car you want to keep for a while, go for the seal replacement. If you don't care how it looks and want to keep it from leaking until it rusts away go for the RTV.

RML · #10 07-23-2009, 12:18 PM

Quote:

Originally Posted by jdh122

. . . Should I be able to pull that inside seal away from the windshield fairly easily, or should it be sealed tight against the glass? I'm guessing the latter. At this point I'm leaning toward purchasing some silicone sealant and trying to seal the area. As I said earlier, the inside seal itself looks quite new.

Is the windshield seal a single piece that encases the windshield, i.e. is the seal I see on the outside of the windshield just the other side of the seal I'm looking at on the inside?

Don't waste your time and money using the silicone sealant you buy off the shelf. MB makes a non hardening sealant that comes in a tube that you insert into a caulking gun. It has a special tip that slips under the windshield gasket. It runs about $29 and is far superior to the black silicone stuff. I used the silicone stuff first and still had leaks. The MB non hardening stuff fixed the problem.

If you use it, be careful not to put too much lateral pressure on the tip, which is about 3" long. It can snap off. Support it with your other hand as you move along your gasket.

It can be ordered here, from this site. It may be hard to find but if you call Phil he can get it for you. It may be a special order part. I think he just has it drop shipped from MB.

charmalu · #11 07-23-2009, 12:38 PM

Do not use RTV, silicone, gasket in a tube stuff. It will cause rust. I have been told by more than one source.

When I had my rear window replaced, with new gasket, the guy didn`t use any sealant, said MB puts them in dry. trunk wasn`t dry when it rained the next night, and that was the reason for replacing in the first place.

I bought some 3M Urathane sealant in a calking tube. it is the same black stuff the glass shops use. I ran a bead of it under the edge of the rubber where it neets the paint. been dry now for the past 3 winters.

The plugs under the rocker panel look as they should. only the one points down and to the rear.

Pull off the inner splash shield behind the front wheels, and take a look behind where it covers the area behind the fender area. I had a rusty spot area where the drain below the battery area (Hinge pocket) dumps into. there is a tube molded into the shield, cut out the bottom on it so it will drain, it backs up dirt and leaves.

Charlie

300D85 · #12 07-23-2009, 01:13 PM

Quote:

Originally Posted by jdh122

At this point I'm leaning toward purchasing some silicone sealant and trying to seal the area. As I said earlier, the inside seal itself looks quite new.

Might do a search of - windshield sealant leak - before going with the silicone

tbomachines · #13 07-23-2009, 01:58 PM

RTV will cause rust only if you don't do a good job sealing it - if ANY water gets in underneath the bead, it will stay there but just do a really good job sealing it up and you should be good.

DSlater · #14 07-23-2009, 04:59 PM

Want to second or third what charmalu said. Had both my gaskets replaced and had new leaks in the rear. The shop used no sealant of any kind that I could see. Found plenty of old sealant remnants under the new gasket that would help allow water though.

Used PL brand black polyurethane roof and flashing sealant under both gaskets all the way around, where they meet the paint _and_ where they meet the glass. It would take an icepick to make a leak around those windows now.

#15 07-23-2009, 05:49 PM

One of the very first real payoffs from mercedesshop back in early 2000 was learning the source of the water in my rear floorboards. I first logged on in January 2000 and at that time I already had almost 13 years of experience driving 123 cars. For the last seven or eight of that I tried EVERYTHING to cure the swimming pools in the back floorboards.

Someone, I don't remember who, pointed toward the hood hinge pockets. My first response was "say whaaaat!?" I might not have even tried their suggestion had it not be for so many years of trying EVERYTHING ELSE. I tried it and never had a wet floorboard thereafter and I and my family together did untold hundreds of thousands of miles in 123's after that point.

Here's the cure:

Open the hood and look for some little dimple openings at the rear of the hood hinge pocket. There is a vertical piece of sheet metal in the middle of this area and there is a little opening at the bottom of this vertical piece of metal that also must be clear. The dimple at the rear allows for a drain between the fenderwell and the firewall.

In addition to those two dimples at the firewall and the two in the vertical pieces of metal, there are some drains underneath the master cylinder and the battery box.

I must warn you that cleaning these drains requires very skilled use of a highly sophisticated tool. This tool is a piece of baling wire (for city folks I'm quite sure that an old coat hanger will provide an adequate substitute for baling wire.) Using your sophisticated, high tech tool clean all six of these drain areas thoroughly.

Do this and I expect your kids will have to find a wading pool elsewhere.

I know it sounds nuts, but it worked for me.