Replacing Windshield Frame Bottom Grommet

[glcaines]

The windshield on my M151A2 flopped around while driving, sometimes significantly. I was able to find an NOS grommet for the lower windshield frame. I had a significant problem cleaning paper from the NOS grommet that was glued all over it. After several hours it is now pristine-looking. I suspect the presence of the glued-on paper was the reason for a somewhat reasonable price. The original grommet was very difficult to separate from the windshield frame. There was some sort of red adhesive spread over the inside of the entire channel on the bottom of the frame. The windshield frame is in very good condition with no rust except for a six inch section in the channel on the drivers side that had some surface rust. I'm cleaning the channel up and will paint it with Rusty Metal Rustoleum followed by 34079 Forest Green paint. I'm assuming that I should put adhesive in the channel prior to installing the new grommet since it had adhesive originally, but what kind should I use? I'm thinking clear silicone, but not sure. I've not been able to find anything in the TMs on this. What are others using?

I'm really having fun working on this truck. I just completed repacking all wheel bearings, replaced the seals, new wheel cylinders and new brake shoes. I had previously replaced the master cylcinder. I also flushed out the brake lines and replaced with DOT 5, which was what was in it originally.

[199th mp]

go to the auto parts store and buy a tube of weatherstrip adhesive. 3M makes a good one, but there are others. read the label. under NO circumstances should you use any product containing silicone. silicone will have a chemical reaction to the sheet metal, and rust and corrosion will set in. never use silicone for anything that touches sheet metal. silicone is fine for aluminum, but not for sheet metal.

[glcaines]

go to the auto parts store and buy a tube of weatherstrip adhesive. 3M makes a good one, but there are others. read the label. under NO circumstances should you use any product containing silicone. silicone will have a chemical reaction to the sheet metal, and rust and corrosion will set in. never use silicone for anything that touches sheet metal. silicone is fine for aluminum, but not for sheet metal.

Thanks, I didn't consider the corrosive properties of the clear silicone adhesive due to the acetic acid release. The existing adhesive in the channel is red, so I suspect it may be red silicone since red silicone isn't supposed to corrode metal. However, I don't know how long red silicone has been in existence and this A2 has been around since 1979. I do have a 1987 FLU419 Unimog that specifies red silicone for sealing some of the steel parts as a gasket, so it has been around at least that long. That being said, I have never used red silicone.

[rickf]

I am pretty sure they did not use adhesive originally. I think what you are seeing is a later sealing attempt since they did not ever seal perfectly. Is this seal still nice and soft? Most of the ones I have seen are pretty stiff after sitting for 35-40 years and they can be a bear to get installed. Luckily you are working on an A2 to begin with since the A1 seals are long gone and the A2 seals are thicker to match the A2 hinge spacing.

[m3a1]

Rick is making a very good point. Install first and check for fit. Then, if you feel you must, use adhesive, but only after all the cursing...

[glcaines]

I am pretty sure they did not use adhesive originally. I think what you are seeing is a later sealing attempt since they did not ever seal perfectly. Is this seal still nice and soft? Most of the ones I have seen are pretty stiff after sitting for 35-40 years and they can be a bear to get installed. Luckily you are working on an A2 to begin with since the A1 seals are long gone and the A2 seals are thicker to match the A2 hinge spacing.

The seal on my A2 was hard as a rock. In addition, the windshield apparently was put in the upright position with something caught between the grommet and body because the seal had a large section where it was distorted from something caught between. The seal wasn't only hard as a rock, it had shrunk up and wasn't as thick as originally. My windshield flopped around 3-4 inches every time I hit even a small bump.

[rickf]

Did you have the pins in the windshield? I have run a windshield with no gasket at all and it never moved. If your pins are in then move the windshield by and and see if one of the hinges is moving in the body or the windshield frame.

[glcaines]

Did you have the pins in the windshield? I have run a windshield with no gasket at all and it never moved. If your pins are in then move the windshield by and and see if one of the hinges is moving in the body or the windshield frame.

The pins were in and the pins were new and tight. All of the hinge parts are tight, both in the windshield frame and the other parts. Normal driving, the windshield never moves. I live on 40 acres surrounded by National Forest and to get to my house, the rocky road has rocks from gravel size up to 4 - 8 inches and I have to drive about a quarter mile to my house over this obstacle course. Just a small amount of movement at the bottom of the windshield frame is amplified by the time it gets to the top of the windshield. Obviously, I drive it very slowly. I'm waiting for the paint to cure completely prior to proceeding with installation of the seal.

[rickf]

If that is the case you may want to remove the windshield until you are ready to install the seal. All that flex will crack the metal around the hinges or at the bottom edges of the frame where it meets the glass. And also let your tires down to around 15 lbs. for those rocky roads, much better ride.

[glcaines]

I finally installed the grommet on the bottom of the windshield frame. The old one was thin and worn out and the windshield flopped around. The new one is so thick it is very difficult to secure the windshield frame upright. It takes two people, one on each side, pulling as hard as we could, to pull the windshield frame back far enough to install the pins. I read someplace that this is a common issue with newer grommets. I was really afraid we would break the windshield, but fortunately it didn't break. After 4 or 5 hours I took the pins out and re-secured it again. It was slightly easier the second time, but was still almost more force than we could pull to get the pins in. The windshield frame is now solid as a rock and no matter how rough the road, it doesn't move. The windshield is now staying upright for the foreseeable future!

[rickf]

It will take a month or two at least for that seal to settle in. But the more you put the windshield down the more likely the seal will leak when it rains. Remember, NOS seals are now 40-50 years old! Rubber gets hard after that period.