Hey,

I'm looking for advice on leaking rear side windows (I think they're called quarter windows?) on my 1985 300tdt wagon. I'm talking about the bigger windows on the sides of the wagon part.

Can anyone tell me what the part number is for those seals? My local shop is quoting $270 each for them (just the seal).

Is it worth trying to use some sealant to fix them? Do I have to use the Mercedes sealant? Or is something else comparable?

Thanks for any advice,

Todd/Louisville, KY

It is usually not the seal itself that is leaking but the channel into which the window mounts that rusts out allowing water to enter the body. So be prepared for costs that will likely excede the cost of the seals alone.

If you are mechanically inclined the rear windows can be removed fairly easily and inspected before committing to a large repair bill.

Basically the trim is popped off, the metal window frame held in place with a couple screws, then you can get inside the car and after removing some of the interior trim fold the rubber seal back and that will allow the entire window with the surrounding metal frame to be removed as a unit.

The reinstallation is the reverse and the method used is the same "roping" technique used for the front and rear wind shields.

I can actually see water coming through in between the black rubber and the window, so does that mean it's the seal?

Thanks
Todd

it has been my experience that water showing between the glass and the rubber can be stopped for an indeterminate time with flow-grade butyl rubber. it appears that the natural bond between glass and rubber relaxes/stretches over time and water can make its way into the seal, around the glass, past the seal on the other side and into the car's interior. the butyl repair essentially bonds the glass to the seal again.

the key to the repair is to thorough clean the area between the glass and rubber to remove the grit and residue that becomes trapped there over time. a tool made of flexible plastic, stiff rubber or wood will permit you to pull back the seal slightly and scrape the area without tearing the rubber seal or scratching the glass. a combination of scraping, blowing with compressed air and wiping with alcohol and drying will sufficiently prepare the area.

butyl rubber can be purchased in a tube (applied with a caulk gun) from big box home improvement stores. it commonly is black or white in color, extremely sticky and is used to seal joints and seams in gutters and downspouts. a specialized version of the stuff is sold through some automotive supply retailers and requires a special applicator-essentially a trigger pump with a metal spout and tip which fits between the seal and the glass and or the seal and the body of the car. the product will not flow as you need it to in cold weather.

insert the tip of the tube or applicator between the seal and glass and squirt a generous amount of butyl as you move around the glass. if your leak is at the bottom of the window you may want to apply the butyl from a point 2-4 inches from the bottom of the seal, across the bottom and up 2-4" on the other side. have mineral spirits and lots of paper towel ready to clean up all residue. you'll want to press the seal tight to the glass after the application and, depending on how much you've applied, you may be squeezing out the excess onto the glass. wipe thoroughly but try not to drip the mineral spirits into the area you've just sealed.

i recently removed the front and back glass from my 1972 220d which i had sealed a year ago and had a chance to see exactly how much sealer had made its way between the glass and rubber. i originally had water coming in between the rubber and glass in the corners of the front glass so i really loaded up the butyl in those areas. on the rest of the glass i tried to stream a moderate amount. after cutting the seals and removing the glass i found a lot of butyl in the corners and a somewhat hit and miss consistency around the rest of the glass. there was butyl around the entire seal but not enough in some areas to really stop water. after treating the area i had no more leaks but if i were to do it again i would take more time to ensure a really good bead all the way around. i'd say put enough in so that when you press the seal to the glass that you are pushing some sealer out.

at best this is a temporary solution to your leak. in the long run seal replacement is the way to go and allows you to inspect the pinch weld beneath the seal for rust and corrosion. the side seals cost around $170 per from MB.

do not substitute or mistake silicone caulk for butyl rubber. good luck.

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Do you know the part number for those side seals?

Thanks for all the info,

Todd

Does anyone know the eom manufacturer of the glass seals in the 123 cars? I have some of the same concerns. one of my side glasses is leaking a might but 3 or 4 hundred for the seals is a bit much. They should be about $150 for the pair. Thanks