1980 300SD Windshield and Rear Window Seals

I've got two rain leaks going on that are driving me nuts. One is in the front windshield which results in water pooling in the heater blower cage. The other is in the rear window, resulting in water
getting into the right rear trunk area. I'm pretty sure they are from the seals.
My question is, does anyone have experience getting the seals on these windows replaced? My concern is, if I take it to a windshield shop, what are the chances that replacing the seals will work? I've had relatively new cars where having the windshield repaired resulted in leaks that were difficult to get solved. If I was relatively confident that I could get this done and it would work and last, I'd be happy to spend the money. The other alternative would be to try to put some silicone sealer under the seals in the areas that are likely leaking. The seals themselves appear to be in relatively decent shape, eg no obvious big cracks, etc., even though they are 25 years old.
BTW, any input on what I should expect to pay if I get the seals replaced?
TIA
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Sure the leaks aren't originating from the sun roof's drains?
Drains get dirty and eventually rust through.
I'd test them before spending any $$ on the window seals.
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"Sure the leaks aren't originating from the sun roof's drains? Drains get dirty and eventually rust through. I'd test them before spending any $$ on the window seals. "
Definitely not the sun roof. The trunk one leaks when sprayed with water along the right rear window area. Front leaks when sprayed along the right side of the windshield, though I haven't been able to duplicate how the water is getting into the blower housing. But I can see water dripping from under the dash, near where the glass would meet the body, though its obviously hard to see, and water can be traveling too.
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OK. Windshield, check that the cowl's water drains (on the firewall) are not clogged with dirt.
Rear window - tough one, some glass shops won't touch it for fear of the glass breaking.
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"OK. Windshield, check that the cowl's water drains (on the firewall) are not clogged with dirt. "
You mean the drains that take water away from the area where the winshield wiper motor is located and that serves as the air intake for the heater? Covered by the chrome grill? I've been there, and water flows right through there fine. Where it enters the cabin is at the very top of the underside of the dash, just about where the window seal would be located.
"Rear window - tough one, some glass shops won't touch it for fear of the glass breaking. "
Is this a problem with the windshield too? That's the kind of thing I was wondering about. Plus how leak free, how long it will last etc. I personally had a new car that needed a windshield and it leaked became a problem. Plus I've heard from other people with similar experiences.
Think I would be better off trying to slip some silicone under the edges of the existing seals? I was debating whether to try that, as I figured it could make it harder to fix if I then decided to get the seals replaced. The silicone would still be on the car where the new seal would have to go and unlesss you were careful to remove all of it, it would seem it could make for a leak with the new seal.
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If you suspect the leaks are around the window seals here's a simple solution: Put masking tape (if possible use painter's blue tape) around the window with the tape flush up against the seal. If you want to be extra careful also put tape on the seal itself, flush against the edge of the tape surrounding the window(s). This will leave you a very thin line between the two. Take a NEW tube of GE clear silicone sealant and cut the applicator so you have a fairly small hole from which the sealant can be squeezed. This hole should allow a bead about the size of the lead in a lead pencil. Using a "hook" type awl, such as that used by window installers, slide the tip under the edge of the seal and pull it all the way around the window to loosen the seal from the body BEFORE you try to apply any sealant. The second time around it is best to have another pair of hands to do a good job. While one person slowly pulls the hooked awl around and under the seal the second person can squeeze in a SMALL "string" of sealant directly behind the awl. Make sure you have a complete string of sealant all the way around the window. If you somehow skip or miss a spot this can be a place for leaks to resume.
As you move around the window you may notice a small amount of sealant oozing out from under the seal. Don't worry. This is why you have the tape around the edge. After you are through take a clean rag and carefully wipe away any excess sealant. You will get some on the tape and that is why it's there in the first place. After an hour or two you can remove the tape. You should have a clean, sealant-free edge to the window seal.
Don't worry about silicone sealant on the painted part of the body under the seal. Any window installer worth his salt will clean that area up before reinstalling a new windshield or rear window should that be necessary down the road. If this doesn't fix your leaks go back and check prior messages in this thread for other potential leak possibilities. Good Luck.
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On 2005-04-21 17:01:13 -0700, " snipped-for-privacy@optonline.net"

Excellent. Any reputable windshield replacement will include a warranty against leakage.
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