OK

I will be replacing a rear window seal on the '79 240D coming up quick, and I would like to use the original Mercedes seal- but it seems there may be drawbacks, mainly because of the age of the NOS rubber. If this seal will end up cracking in a couple of years, what is the point of installing it? I did read somewhere the aftermarket seals have no groove for the aluminum trim, and don't exactly fit well.
I am a little confused about sealants as well. From OEM bedding compounds to urethane and silicone sealants, there are a lot of suggestions.
Now one may get plain lucky and have a quick "snap-in" replacement job that will withstand the firehose test; but if extra sealant is applied, there could be a problem down the road, if, perhaps, a wayward albatross went through the back window a week after installation. You would be facing the job again, and the sealants you installed may hinder your efforts.
As far as I know, silicone-based sealants do not like to adhere to silicone-based sealants. I used to apply them professionally, with certifications, and any damaged sealant had to be removed completely, and adjacent remaining sealant was to be roughed up to provide a "bite" for the new bead.
Bottom line is that if there is silicone residue, you will get a poor seal if you are using silicone.
I imagine everyone installing a window would hope the job would not leak, and last a long time.
As I understand it, window glazing putty is used in place of OEM bedding compound?
I usually coat rubber (suspension, pump diaphragms) on all exposed surfaces with Sil-Glyde to hopefully protect the rubber from exhaust gases, and the vacuum pump diaphragm from engine oil. I am wondering if Sil-Glyde could help protect the OEM seal from splitting.

I know this has been long, but some of the subjects are 15(!!!!!) years old on this site, and those NOS seals are now TWICE as old. I am hoping we can visit the subject of NOS (with emphasis on OLD), and the long-term results of repairs done, and how they have held out over the years (or days!) so we can update ourselves on these repairs.
My current experience includes the pump diaphragm replacement, and I will say that I had no luck with Meyle; the current diaphragm has lasted over a year on the 300TD, but no more miles have accumulated after the year; the pump was removed and inspected, and there is no evidence of impending failure on the diaphragm. I cleaned off the diaphragm, (electrical parts cleaner), and re-installed but it hasn't been driven. The brand on the package? Effbi- purchased here at Pelican Parts, but no longer available? It was my first round with this brand, and so far it is the best for the purpose.

I'd like some input- nobody wants to work on a car. But when they do, I am sure they do not want to do it over again (as I have had to).

Let's go.

snapped_bolt

__________________
'81 240D For now, a good place to borrow new parts
'80 300TD Probably will be put back into service!
'79 240D BACK IN SERVICE SINCE 09/16; limited use, oil leak. Guide pin r/sealed/replaced. Still a leak. Front crank seal....

Whom ever makes the seals for URO doesn't do a bad job in the windscreen department...

I am running URO windshield seals back and front.....I've even reused one....

I have no leaks, seals haven't cracked after 5+ years and I used NO sealant...

You MUST install the chrome in the gasket BEFORE you rope the windscreen into the opening...If you don't install the chrome, you will never get it in....

Also removing the chrome, you want to cut it out of the old seal, don't bend it at all or you'll have a nightmare trying to reinstall it....

Also when you clean the window opening, you will notice on the bottom channel there are two drains that should be unclogged....these drain into the trunk thus how water gets in the trunk from a bad seal...

Also use dish soap when reinstalling....You can use the glazing putty but honestly I have seen no need for it...

I also have a door seal installed made by uro, it was a tad bigger but after 3+ years it has shrank to fit...odd...

BUT I don't recommend URO parts for anything put seals!!!!!!!!!

__________________

I screwed around with water in the trunk of my '82 240D for a while , I always use OEM windshield grommets fore and aft as they last longer and leak less .

I still always had a bit of water in the trunk after rain , in time I discovered the damn fuel overflow pipe hose wasn't properly fitted to the inside of the fuel filler recess , that was a 3 minute fix .

So far no more water in the trunk .

You have to remove the bulkhead to see this hose and if it's in place with the clamp properly positioned .

Just a thought .

I always take the time to clean , polish then wax the pinchweld whenever a piece of glass is out , you can easily add sealant after it's re installed by using
a small nozzle then wipe away any excess that mooshes out .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I thought I had read that aftermarket seals made no provision for installing the trim. They do? I may go that route.
I know if the fit of the aftermarket seals are a bit dodgy, it could prove difficult to install them correctly. But since I am working in the garage, I can take my time.
I would think that sealing the windows seals shouldn't be impossible. It would be nice if the sealant manufacturers would get off their hind ends and offer various application tips as there are in the aerospace industry.
Take for example the outer perimeter of the seal itself. Applying a sealant to the perimeter would no be effective as applying sealant with a wide, narrow nozzle with a poly "wedge" attatched to pull up the seal itself in front of the advancing sealant being applied. There should be a slight excess applied, and the excess should be wiped off immediately. The seal should be gently coaxed back into position, but not fiddled with enough to cause excess sealant to be squeezed out, and form a possible leak path.
My window looks like cartoon stick people applied leftover aquarium sealant to the window. If nothing else, the massive buildup forms a nice dam to catch the most water so it has the best possible opportunity to enter the trunk.
Out of curiosity I just may remove the silicone, apply window sealant under the seal, get the squeeze out, and then apply a single-pass full width fillet to finish.
Is half the fun just trying to figure it all out?

Later

snapped_bolt

__________________
'81 240D For now, a good place to borrow new parts
'80 300TD Probably will be put back into service!
'79 240D BACK IN SERVICE SINCE 09/16; limited use, oil leak. Guide pin r/sealed/replaced. Still a leak. Front crank seal....