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Sunroof Seal Repair

Thu, 04 Feb 2021 15:12:08 GMT

I recently acquired an 87 420SEL and am in the process of bringing it back to health. I’m getting moisture in the cabin and fogged windows and am pretty sure the culprit is the front/rear windshield seals as well as the sunroof seal. I have tried a few places in the area and no one will touch it including my local MB dealer. Located in Bucks County PA. Any suggestions?

190E fan
Thu, 04 Feb 2021 17:50:22 GMT

Congrats on your recent purchase. The W126 is one of MB's best. Thanks for getting it back to health. I would suggest contacting the MB Classic Center in California and ask what they would recommend.

Thu, 04 Feb 2021 21:51:13 GMT

Thanks! I’m really crazy about the car, an can’t wait to get it back to fighting trim. I actually called MB Classic and they unfortunately were not able to help either.

Fri, 05 Feb 2021 05:05:57 GMT

The ability to keep a car like this in nice shape depends on the availability of repair parts. While you may not be able to find needed parts, even with help from people in a forum like this, there are body repair specialists who have managed to make connections to part sources. So your task is to find such an outfit. Inquire of everyone you meet and sooner or later you will find a place which is able to fix leaky windshields and sunroofs properly. So as not to spin your wheels too much, determine which of these two is leaking by the process of elimination. The simplest way to do this is to tape around both the windshield and the sunroof using painter's masking tape and driving the car in the rain. If moisture still gets in it means that neither the windshield nor the sunroof is the culprit. There is no shortage of suspects. If no moisture is getting in with the tape in place, remove the tape around the windshield and see what happens. If moisture is now getting in you know that the windshield is a problem. Now put back the tape around the windshield and remove the tap e around the sunroof to see if moisture is now getting in. This process is a bit time-consuming but simple enough and it will eliminate guessing and unnecessary work.

Fri, 05 Feb 2021 12:25:28 GMT

Thanks I’ll give it a try. Part of the adventure is tracking these little problems down. I’m sure over time I’ll develop some good resources for ongoing care.

Sat, 06 Feb 2021 04:17:28 GMT

i think you have likely misdiagnosed your issue do check your sunroof drains and make sure they are clear. however, the number one reason for fogging is a broken left evaporator drain tube on the w126. the air con in your car runs even with the heat on, and if this foam tube ruptures it will cause moisture to build up in the car. you may also want to check the tail light seals, and check around and under the rear window for rust.

Sat, 06 Feb 2021 10:31:21 GMT

Many thanks for the info! Sunroof drains are clear, and no indications of rust around the rear windscreen but I will look into the evaporator drain tube. Currently the antenna seal is being replaced as well as the trunk and taillight seals so we'll see if that makes any difference.

Sat, 06 Feb 2021 10:36:48 GMT

I'm also getting wet carpet on the driver's side footwells, especially in the rear. Could that be related to the evaporator drain tube? It seems weird to get moisture there from a bad seal and not see any other evidence of dripping anywhere

Sat, 06 Feb 2021 13:01:28 GMT

As recommended above check the windshield and rear window seals. They dry out with age and water seeps between the glass and the rubber. Look at the lower corners in particular. The water migrates down and shows up under the carpets. You can caulk between the seal and glass and that often will stop the leakage but replacing the seal in accordance with the workshop manual procedure is the best solution.

Sat, 06 Feb 2021 20:54:33 GMT

I think for the short term that’s what I’ll do while I seek a proper solution. I just don’t want to have to worry about driving it in the rain, or encouraging rust either.

Sun, 07 Feb 2021 13:25:16 GMT

Roger pch on the drain tube.. If you can, crawl into your trunk with a flashlight and have someone you love and trust run a garden hose around the perimeter of your closed trunk lid. You will probably quickly find your major leak. Unless the car has been garaged it's entire life you will find that that the channel around your rear (and probably front) windshield is rusted out. No amount of silicone squeezed into it will permanently repair this problem. While it may be discouraging, rebuilding those channels is a common body shop repair and costs less than you may think. As I recall, doing so on my 1983 300CD cost me about $350 plus a new gasket and paying a glass shop $100 to r&r the glass. Well worth the modest expense for a great classic ride.

Sun, 07 Feb 2021 15:01:56 GMT

the water on your rivers floor is almost certainly the evap drain tube.

Sun, 07 Feb 2021 15:02:08 GMT


Drew Webb
Fri, 26 Feb 2021 23:17:37 GMT

Let me add a potential info source: Pierre Hedary MB in Titusville FL. GIve him a call, or email him at MBownersforlife@gmail.com. He’s very good about helping folks, and is a specialist in classic MBs. Be patient, because he and his wife have a baby due momentarily, but he’s a good guy and will respond. Your 126 is well worth the effort to restore it- I still miss my ‘84 300SD.

Fri, 26 Feb 2021 23:34:07 GMT

Drew, the post above yours is from Pierre.

Sat, 27 Feb 2021 12:33:23 GMT

In the meantime I’ve put some change into replacing worn and broken items which has vastly improved overall performance on this fantastic machine. I’m thoroughly in love with it and very much prefer it to my ‘19 CLS. I didn’t expect to get so attached but at this point I don’t think there’s a limit to what I’m willing to do to bring this car back to full glory.