Replacing a rear window seal - PeachParts Mercedes-Benz Forum

rwthomas1 · #1 04-23-2003, 10:14 PM

Okay I have cut the seal out and removed the rear glass on my '84 300D. Someone has been in there before as it was all gooped up with some sort of grey play-dough like caulk stuff. I have a slight bit of rust on the steel lip where the seal sits that must be dealt with. There appears to be a drain hole in the lower window channel just inside the lip on one side. I have come to some conclusions because of this hole. The rubber gasket seals the glass on one side and the metal on the other. The rubber/glass seal can be made perfect by using a little "flowable silicone" after the install as there is no way water can be trapped at this point. The lip seal on the rubber gasket that seals between the body and the gasket cannot be a perfect seal so some water must get under and run down into the channel in the bottom/back of the window. The hole that drains into the trunk must be there to drain the little bit of water that may get in. As long as this water drains off there is no way it will build up and pool causing rust or leaking past the interior rubber/metal lip seal. Since the rocket scientist that used the grey goop to seal the window also sealed up this hole the water had no way of escaping. This is obviously not good. I believe the MB designers wanted the water to drain into the trunk. They knew it would be very little water and the trunk also has drains in it. There is no way they would design a car with a trough that would fill with trapped water, that wouldn't make sense. Anyway, I am trying to remove the grey goop. Scraping with a wood paint stirrer to keep from scratching things up. I would like to get all of it off. Anyone know what solvent to use that won't hurt the paint? Thanks, RT

BIGRED · #2 04-23-2003, 10:34 PM

Not sure about your conclusion.

In my manual it says ...

" 12. Install ornamental frame in rubber frame.
NOTE: Prior to mountin gcover, fill upper join of ornamental frames with MB window sealing compoung so that no water can flow under cover over back window"

"16. Make seal between glass and rubber fram as well as body and rubber frame with MB window sealing compound, Part number 001 989 31 20.
Note: Excess sealing compound can be removed with adhesive tape."

I assume they mean to say that there would be adhesive tape applied around the window opening ahead of installing window, but there is no mention of it.

Good Luck
Don

leathermang · #3 04-23-2003, 10:55 PM

"grey play-dough like caulk stuff. " = MB window sealing compound, Part number 001 989 31 20.

It does show a regular caulk type gun being used to apply the stuff... so much for the " glue or not to glue " question...

leathermang · #4 04-23-2003, 10:58 PM

Have you tried
3M General purpose adhesive cleaner 051135-08984 ?

leathermang · #5 04-23-2003, 11:02 PM

BIGRED, It is common in paint shops to use wide masking tape wrapped around one's hand to pick up any runs in paint ( as soon as it starts to run..... so they may have meant that trick on the excess caulk.....given they did not say before hand to apply it... although that would seem a better method to me.... very easy to make a clean line that way...

rwthomas1 · #6 04-24-2003, 12:23 AM

Yeah,
I have the manual too. There was so much "caulk" on mine I have trouble believing MB did it. Also since the drain hole was quite deliberately caulked shut I have questions about the skill of whoever did it. If the install/caulking was done correctly then you wouldn't need to fill the hole.... Also the caulk was not applied completely around the window mostly on the sides an corners with none on the top/roof section and none sealing the glass/rubber joint and none at the ornamental frames joint. Then they just used so much it just didn't make sense. Regarding "to caulk or not to caulk" there has been some debate about using any sealant/caulk at all. I believe TXBill recommends not using any..... Also I remember reading that the MB caulk was not readily available. I will have to ask around tomorrow. Oh yeah, Exxon regular unleaded removes the old caulk quite nicely. Thanks, RT

rs899 · #7 04-24-2003, 06:45 AM

rw-
I found the same grey goop in copious amounts(and rust) when I replaced my rear window seal last year. So, I assume it was put there by the factory. And I think I used gas to remove it as well. I did not replace it , but my new seal leaks a bit at one corner, possibly because I did not perfectly center the glass. I have since added some non-silicone sealer to that area which seems to have stopped the leak. Be careful with that glass - it is awfully thin!

GregS · #8 04-24-2003, 09:11 AM

You guys are replacing your rear window seals yourselves? Can someone go into more detail on this? How do you remove the aluminum trim? How do you remove the window without breaking it? I need to do this and would love some more info. If its possible to do it myself, all the better!

Thanks,

GregS
'84 300D, 173k
'90 300CE, 163k

rs899 · #9 04-24-2003, 01:50 PM

I did it somewhat successfully- at least I didn't break the glass and eventually stopped the leak. But if you look carefully on mine, the trim is lifted off the rubber on the bottom edge. I would cut the seal wherever possible , perhaps in several places. Do not pull on the trim any more than is absolutely necessary. The glass is very thin and getting the gasket on it while it is off the car is like working on a time bomb because the gasket must be stretched so much and the glass is curved. It goes on in theory like any other old-style glass , pulling string from around the inside lip of the gasket from the inside while a helper pushes on the assembly from the outside. I only did it because no shop would guarantee they would not break the glass ( I understand now) and I wanted to be sure that I could fix any rust in the channel myself.

leathermang · #10 04-24-2003, 02:42 PM

RS899, That last point has always been why I did my own gaskets... I wanted to fix the rust ( I always have old cars ) and it takes at least a day to do that right... I usually put epoxy paint on that area....
I will make a glass holder this next time... they show one in the manual... mine will have two of the suction cups mounted upside down with universal joints holding them... so the pressure on the curved glass can be determined by the glass at whereever it is placed on the 'table'.... will make pics of it , naturally...

rwthomas1 · #11 04-24-2003, 06:56 PM

I'm with rs899 and Leathermang on this one. I'm not signing any waiver, handing over $90 only to watch some chimp bust the glass and then charge me for another. If I break it then I can deal with it. I called the local dealer today and ordered the correct MB "sealing compound", will be in tomorrow. I have read and reread the MB installation instructions and it seems that you are supposed to insert the tip of the "sealing compound" tube under the lip of the gasket on both the glass and the metal seal and shoot a bead in all the way around. Looking at my car, from the copious amount of goop that was there and some tool damage on the underside of the aluminium trim pieces I surmise someone has been in here before. Regarding removing the glass and trim its fairly easy. I cut the rubber seal around the glass between the glass and the trim with a utility knife. The first cuts I made at 90* to the glass, then more at a steeper and steeper angle under the trim. Fishing out the cut slivers of rubber and pulling them while cutting really helps. Once you have cut all the rubber you can away then push the little trim joint caps aside and GENTLY pry the trim up and out. Gentle pressure from the inside on the glass will break the seal. Work your way around the perimeter until the seal is broken then remove glass. Not to bad really. I have a few small rust spots that are getting wire-brushed with my Dremel and then coated with POR15. Hopefully the glass will go back in tomorrow. Wish me luck.... RT

leathermang · #12 04-24-2003, 07:13 PM

GOOD LUCK !

psfred · #13 04-24-2003, 07:29 PM

Best way to remove the window is to lift the lip on the inside and roll it over the metal flange. The reverse of putting it in. If it won't roll, due to stiffness and age, cut it off, or cut completely through the gasket. You may have to do that anyway if someone glued the seal in. Some cars will pose problems here -- the W108 rear trim completely covers the rubber, no way to cut through, I'll probably have to cut the retaining lip off from the inside.

What you DON'T want to do is remove the trim first! You will only bend it all up and get frustrated, and it falls out when the window is out (its also a devil to get installed at the corners on the new gasket, too!). Pull the window and seal with the trim in place, then flex the gasket and remove the trim. It's perfectly all right to cut the old gasket off once it's out. You will also need to remove any crud on the glass.

You must pull the base trim -- it clips on to the body on the W115, W108, and I think the W123/W126 chassis, but I've no personal experience with the last two.

The MB sealant is a new thing, wasn't used at the factory. I've seen some caulk type material in the corners on my brother's 75 300D, but it could have been put there post factory, the front windsheild was an aftermarket. I am quite sure the black crap the typical auto glass place uses is NOT the correct material, ditto for any RTV type sealant. The gasket takes a week or so to settle in and seal all the way around, any sealant the hardens sooner will cause leaks.

Peter

Fredmburgess · #14 04-24-2003, 09:37 PM

Hey RW,

I had a guy with Mercedes experience R/R the seal on my rear window and windshield (I bought the seals from Fastlane). The car had huge amounts of that lovely gray caulk, especially in lower corners. My window guy believes that is factory install as he has seen it on all the cars he's done. With age its just powdery junk when dry, sloppy stuff when wet. We cleaned it all out, wire brushed and touched up a few rust spots. He taped put the seal on the glass, trim in the seal, installed in a dry opening. Masking tape on the paint all the way around the seal, then used a standard caulk gun - tip under the seal, pumped the opening black silicone all the way around the opening, completely filling the lower corners. If that hole was a drain, it isn't anymore!

So far I'm a year into this with no leaks. Time will tell if water is trapped causing rust, but think it's sealed pretty well.

Fred

rwthomas1 · #15 04-25-2003, 12:45 AM

psfred,
Some of the grey goop I removed was quite flexible and very sticky so it doesn't seem to ever really harden which is good news as it will continue to move and seal as the rubber ages. I am not planning on filling the entire window channel with sealant just looking to lay down a bead about 1/4" wide. I am getting the MB stuff just to make sure I am using the right thing. I guess time will tell. RT