How difficult a DIY project is removing rear windshield on w124?
 

I've got a bit of rust that's been lurking on the side of the rear windshield on my 300D for several years. Since I'm in the midst of a massive rust repair project I was considering trying to get to that too. I already have the hat shelf and C pillar trim out because I'm re-dying the shelf so I was thinking it might be the best time to remove the glass. However, looking at the FSM, it looks like it's a pretty complex job. So I'm debating whether to pile it on to the other complex jobs I'm doing now.
Anyone done this as a DIY and have advice on whether I should do it, or try to have a professional take it out? The glass is fine, by the way, just want to access the rust.

I don't think the back screen is bonded. If I'm correct I'd investigate the cost and availability of the trim pieces that will almost certainly be nadgered by the time you take them off.

If it's held in with a rubber gasket it's pretty simple to remove. Simply get a supply of good blades for your utility knife (I like Stanley brand) and cut the rubber until the glass comes out. The old rubber will be dry and pretty inflexible so you'll have a heck of a time trying to pull the glass out of the rubber like you would on a newer car (I've gotten inside and simply pushed glass out with my back but that's not likely here). Of course, you'll need to replace the rubber but it's almost certainly time anyhow and in fact that may well be one source of your water leak in the first place. There may be a metal trim piece that's held in with the rubber - be sure to save that so it can go in the new rubber.

If it's bonded in - THAT"S a stinker. I only pull bonded glass if it's cracked anyhow so there's nothing to lose. Otherwise I have the pros tackle it. They can usually save the glass.

I always have pros reinstall the glass. I know the drill but they have tools and sealers that I just don't have and besides, it it leaks you can take it back and make them fix it. It usually doesn't cost too much.

Just an FYI - the rear glass is not called a "windshield" - that's the front glass. The correct term is "backlight" though "back glass" is often used or simply "back window". No big deal but I thought I ought to let you know.

Dan

Remember to remove the sail panels on both sides in order to disconnect the rear window defroster wires.

I diy'ed (roped in the rear glass) on my 85 W123 300D because it is NLA and did not want to chance letting a shop F it up like they did on my 83 300D windshield. It was easy, came out perfect with no leaks.

I know nothing about W124 glass so google is your friend. Per this training video from Mercedes, the windshield is bonded https://www.youtube.com/watch?v=PcJTtMBqoqY . I'd guess the rear glass is also bonded.

After seeing the video, I'd suggest paying an experienced shop to do it. Look for a shop with a mechanic who has been working there for 15 years or more, longer the better. That rules out most Safelite and other chains.

Edit: First sentence in video says both windshield and rear window are bonded.

Thanks ... I did find that video last night but wasn't sure the significance of it being bonded as far as turning the job into something one can do at home. Not sure if that makes sense, but I guess I just mean sometimes something looks very complicated in the official procedure and then someone here has figured out an easier way. So that was why I asked. It sounds like that is not the case here. I will probably just try to get a professional to pull it in the spring. Do you think I'd be able to get someone to remove it but not put it back in, so I can do the rust repair? And then have them come back and put it in when I'm done?

That w124 bonded rear window is a pain to remove but it's doable. You'll need the windshield cutting tool. Basically a razor blade knife with an extra long handle for leverage. If can't find one, then don't do it. Too much hassle.

Your local glass company should be able to just remove the glass for you. They are always looking to make a buck. Then they should be happy to reinstall it when the time comes.


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That's been my experience too. Of course, they usually pull the glass and put in a new one but if the shop's any good they'll handle your request w/o hassle. If the shop is NOT any good you don't want them anyway!

The reason it's so hard to get these out - they're held in with a REALLY tough adhesive (no, it's not RTV like bathtub caulk) that was especially invented for this. I'm not sure if they were the first but Morton Thiacol (sp?) was early in this game and the adhesive is often called "Thiacol". Remember, the glass is expected to stay in place even in the even of an accident. They went to this because the glass stays in place better and is much less likely to leak though of course everything ages.

Anyhow, the only way to get these out is to cut ALL THE WAY THRU the adhesive which is not as easy as it sounds. The pros have an assortment of tricks and tools to get this done including a heated knife that is often pretty helpful. I've bought some of the tools but still had mixed results and I decided that it was cheaper to have the pros do it if the glass was worth saving.

EDIT: The best paint durability requires that the windshield and back glass are out anyway. It's the only way to clean and get paint into the window channels which will protect those areas against rust. If you pull the trim and try to paint up to the glass the rust WILL come back. So you're doing the right thing!

Dan

Interesting, and indeed sounds like more effort and risk than is worth it to try myself. I'll just get someone to pull it off for me and then I can take my time on the rust. I had put a little POR15 on it a few years ago which staved off major spread but I have no doubt it will need work under the glass ... maybe even new metal welded in. I'm trying to do really thorough repairs all-around on the rust on this car so I definitely want to do it right.
I do recognize the name Morton Thiokol from reading about the space shuttle Challenger ... they designed the rocket boosters and were at the center of the fallout after what happened. Did not know they also did the window glass adhesive. I'm assuming that's the same company though.

Thanks very much for the info, everyone. Definitely helped make my decision. :)

Searched eBarf (windshield removal tool) and found a few options. My neighbor across the street does glass. We replaced the windshield in my 4Runner earlier this year and he used a tool like this to cut the old seal:

BLUE POINT TOOLS YA 109 - A WINDSHIELD REMOVAL KNIFE & PULL HANDLE | eBay

Blue Point is good stuff and that's probably a good price. The one I bought was an off-brand and it just didn't work very well - I'd expect this to be better.

Dan

It can be done at home for sure, but like anything else, do the research and get the right tools and learn the techniques for the job first. Approach it the same way as you have with rust repair and you'll do alright. Look at youtube videos on how the hand pull knifes and long razor knifes are used (I don't think you want to invest in power tools, which may make the job easier but certainly not a must). If you can, find a junk W124 rear glass to practice on.

Beware when cutting the urethane that you do not pry and bend the edge of the glass which is the weakest. The front windshield is laminated, which will crack if you pry too hard but it will stay as one piece. The rest of the glass on a car is tempered glass, which breaks by shattering in a million pieces. Using the pull knife like the Blue Point linked to looks easy if you watch videos of pros using it. But it requires skill in order not to break the glass. Even with a pro, he cannot guaranty that the glass will not break on removal or install, since the glass could have been weakened from age or stone chips, or it may not have been properly tempered when it was made.

I don't know how difficult it would be to find a pro who will pull the glass and then come back later to install it. Two trips instead on one, more time = higher cost. Let us know how you make out and take lot's of pics.

Funny that this came up ,2 days ago I had a frt windsheild put in and was told by the installer that they fff-d up the trim .It took me awhile to cool down because it was expressed they knew what they were doing after I went over the age of the car and how important the trim was to the install (critical).I checked with the dealership on the 3 chrome pieces ,$210 each x3 $630 for just those chrome stripes that are the structured pieces between the glass the seal and the windshield .If your cutting out the seal youll want to cut on the outside of the chrome ,their is a lip inside the seal at this location which grabs the seal .This will allow for you to peal back the part youve cut away from the seal and out of the way.You then can gentle tap outthe chrome with a small handled flat edged tool much like a trowel ,take your time to not bend the piece. Good luck.A heat gun will also help

What year model windshield of your's got fff-d up? Subject title is for W124 with bonded glass, trim is not pressed in the rubber seal like W123's. Windhshield install technique totally different.

Funnily enough I have a chunk of a W124 that includes the rear glass ... I got it a long time ago in case I needed the metal around it to replace the metal on mine since I knew that was a rust-prone area (or in case I needed the glass). So, since I need to get to the metal on that anyway, it'll be a good trial run to see how bad it is getting the glass out. I hadn't even thought of that, thanks for the tip.

It'll be a while before I get to this (probably will try to finish rocker panel and floorboard repair first) but I will update when I do. I had started a thread on all the repairs I'm doing but kind of got lazy with updates ... or rather just overwhelmed with the work itself. But at some point when it's all done, I will upload a ton of photos because they might be helpful to others who want to do rust repairs.