[W126 Coupe] question for anyone-front glass windshield details

[Gary]

thanks so much for the info and yes i would like your instructions/pictures.  thanks again.

Dick Spellman <spell.yy at verizon.net> wrote:Alex and Gary:
 
The front windshield requires that the old factory butyl rubber be scraped very close or right down to the metal or primer.  The glass guys use an electric knife of sorts to skin the old adhesive away.  Then they apply a brush on primer which sets up almost immediately followed by a heated sealant bead (using a battery operated caulk gun with a fresh tube of heated goo just removed from the glass truck oven).  This double wide bead is applied in one continuous loop(they may lap it where necessary) all the way around the frame opening where the glass will be seated.  When the glass is carefully set in place it makes an air and water tight seal.  The only other detail of great importance is setting the upper chrome strips (2) in place so the clips engage at the roof line.  So, it is very important to set the glass and within a few minutes set the chrome so if the glass height is too high they can press it inward so the chrome lies flat.
 
Bottom line is that no rubber seal is involved in the front windscreen replacement.  I would recommend that anyone doing their front glass remove the chrome strips at the roof line which is very easy to do, in advance of any scheduled work so you can check for any loose clips or corrosion before they set the new glass.  This will give you time to Dremal sand any flaky or rusted areas and treat with POR 15 and in the case of a broken clip (very common) order them up from the MB Dealer and be prepared to pop rivet (stainless or aluminum stud, 3/16 inch grab & no washer) the replacement clips in place.  I've done the clips on two cars immediately after the glass guys remove the old glass and prior to applying their primer and goo.  I added a small amount of silicon to the back of the clips and the stud hole in the roof line before popping the rivets.
 
Just as an FYI, when these clips are found broken by the glass folks, they simply ignore them and rely on the adhesive overflow to hold the chrome.  This is fine except if a pinhole exists where the old clip used to reside, you'll get a phantom wind noise while driving.
 
By having the chrome strips off the car you have two additional opportunities.  First it's perfectly safe to drive the car with them off and second there is a fine urethane film on the back of the chrome which serves to dampen any vibration while driving.  Make sure this film is glued down wherever it has moved or become loose and clear off any fine particles or grit.
 
I'd also go ahead and remove the side aluminum reveals and painted chassis trim (the glass guys will anyway) and polish it up with a good wax and sealant like Klasse AIO and treat the side rubber chassis rails to some Meguires Purple goo used to restore rubber and sold for tire dressing.  Last item would be to inspect the rubber seal along the windshield wiper transmission cover where it meets the lower edge of the glass and replace if it's showing cracks or corrosion (more for looks) and replace the rubber donuts that sit at the base of the wiper arm linkage stubs.
 
If you choose to go one step further (again the glass guys do this anyway) with the wiper arms off, the screened wiper transmission cover removed you can check the central drains, check the drain hole at the partition to the blower fan inlet on the passenger side, inspect and replace the rubber/foam that sits atop the partition, inspect windshield heater bladder hoses where the wipers park and inspect the wiper linkage bushings for cracks and apply a liquid gel lube where possible.  
 
While all of the above may seem like a lot of work, it's one of the easiest jobs and takes no more than an hour.  I have photos of the steps for the 126 if anyone should need them.  So, if your car is a 'keeper' I'd do it.  If it's a daily driver with just so many years left than I'd skip it all together with the exception of checking the clips so you don't end up with new glass and a mystery wind noise as a side effect.
 
Dick
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