2 cracked windshields

[TimK]

Facts:
1. Removed windshield frame (did not remove glass from frame)in 2008 and reinstalled.
2. In 2011 the windshield developed a stress crack on the drivers side while parked (maybe over the winter, can't remember for sure).
3. Windshield replaced in August 2011. Drove car a few hundred miles without incident, then parked for the winter.
4. Today I removed the car cover and discovered another stress crack on the drivers side that occurred over the winter while parked.

This is too much of a coincidence to ignore. I'm not about to replace again without figuring out why this is happening. Does anyone have some thoughts or similar experiences? There was a shim in the left side frame post which attaches to the body that I removed and replaced. I'm not sure how to fix and be sure it doesn't happen again. It was not fun to replace the glass and get all the rubber trim correctly installed let alone the expense of the glass itself.

 

[drambuie]

wow... It is very fustrating to even hear about it! I have to wonder if there was a defect in the glass itself! In cold weather everything should contract and not expand! I would think all edges of the glass are insulated by rubber? Maybe there was a very small hairline crack in the glass before you installed it? Or someone made contact with it while in storage and did not tell you! My local glass installer refused to even try to fix mine! said it wasn't worth there time for all the work and was afraid he would crack the new glass! He freaked out! He did not understand that all i wanted was a small crack to be stabilized. I know installers crack new glass all the time! Most so called pros wont even change a tire on a vintage car! At least you have some experence changing the glass and chrome trim. That is the bright side! I wish you would document and share your procedure with all of us. I dread having to do it someday. If i where you i would carefully inspect all contact points 360 degress around the glass as you remove it as well as the chrome trim that may be the problem. Also i would push back and forth on the glass before you remove it, to see if you had slop around the seal after you installed it last time. If you did, Then hitting bumps would begin the process of cracking. Or.... the frame posts are way out of alignment! Just my thoughts. Michael, New lenox IL.

 

[TimK]

Thanks Michael (drambuie) for your response. I would be happy to share my experience with replacing the glass. I ordered it from Moss and it came very well protected--encapsulated completely in spray foam insulation. It was in perfect condition. It also received all the new rubber seals needed to install. I also got new corner brackets. The biggest problem taking out the old glass was getting out the 8 tiny screws holding the corner brackets to the frame. I had to drill them out. Because I got new brackets and screws that was no real problem, just time consuming.

With the frame disassembled, I removed the glass. The next hard part was putting the new edge seals on all four sides of the new glass. My wife helped and suggested we put strips of Scotch tape every inch or so to hold it in place while we fitted the frame and screwed the new corner brackets in place. It seemed to line up pretty well. After the frames were in place I trimmed the Scotch tape with a knife. I did the work on my pool table which has a nice felt surface to protect the glass and it was the right height to work on standing up. I don't dread doing it again, but I don't know why it happened twice in a very short time span and both times it was parked covered in the garage.

 

[BoyRacer]

I'm inclined to think that there may be some kind of stress induced into the glass because the stanchions are now slightly out of alignment. Maybe that shim that you put back wasn't put back in exactly the same place and therefore, created a misalignment of some kind. With the next replacement windshield, I would loosely attach the frame to the stanchions and gradually snug up the screws. Check for gaps or any misalignment even if you have to use a feeler gauge. You might have to loosen up the bolts holding the stanchions and use some very thin shim stock, or readjust that old shim, to make sure the stanchions align up perfectly with the chassis, and the windshield frame, when you tighten everything up.

 

[TimK]

Thanks, Richard. Your analysis is similar to mine but yours goes further and gives me a line of approach. I suspected the stanchion/shim but didn't know how to get it right. Just to be sure, I was talking about the part of the stanchion that attaches to the body. That's where the shim is. I wasn't thinking about where the stanchion attaches to the glass frame, correct? I mentioned that I had removed the whole windshield assembly in 2008, but didn't mention I fumbled with exactly how the shim was placed. That is the thing that is common before both cracks. The second time I reinstalled the assembly, I put the shim in where I had put it in the first time.

 

[Randy Forbes]

I agree with Richard too, but if you're still a little gun-shy, next Fall when you park the car, go ahead and loosen the stanchion to body bolts a couple turns.

Leave yourself a note (a China Marker will write on glass, and can be wiped off next spring) to remind you to snug the bolts up again.

Obviously, if it cracked a third time (besides you becoming our resident expert on windshield glass changes...) the stress/twist would have to be within the glass frame itself.

 

[TimK]

Thanks, Randy. Good advice from all three responders. I really appreciate the thoughtfulness of everyone here!

 

[RAC68]

Hi Tim,

Although I appreciate the line of reasoning that has previously been extended, I would expect the rubber windshield edge seal to provide sufficient flex space to compensate for some small amount of misalignment. It doesn’t sound as though you had a great amount of difficulty installing the glass into the frame and you would certainly know if you had to force the glass in place. Also, I would expect that you would also be aware if you had great difficulty mounting and tightening the windshield onto the car.

If you are using the original rubber seal, I would suspect that there could have been a bit of glass or other type of foreign particle left behind. The stress crack could have been started by driving vibration around this foreign particle when the glass was first installed but not progressed past the seal until the car’s winter snooze when the cold temperatures caused the glass to contract and further the progression of the crack to where it became obvious.

Like checking the inside of a tire after a flat, I would suggest checking the seal (especially at the point of the crack) for foreign matter or any protrusion extending from the frame channel.

Another thought,
Ray (64BJ8P1)

 

[Kawalex]

When I got my BT7 it had a broken windshield and so I bought a new one, gave it into the frame and stored it (stressfree I thought) over some years as I had no time for my Healey over years.

When I finished the restauration last year I fetched the windshield from the shelf and was very surprised that it was cracked again (at nearly the same plosition as in Tims first picture) - so I had to order a new one and to do all the work once again. I had no idea how to do the work better and so I did every thing same as the firt time - of course also new rubbers as the other ones were a little bit hard after the years in storage. Now afert one year the windshield is still fine and I only wanted to mention that I am not sure if it helps 100% to loosen the frame-bolts for getting the glass stressfree. Maybe it is a problem glass internal stresses.

Sorry for my english but I hope you know what I mean.

 

[andybj8]

Tim

I know the screens are different to my bj8, but my experience was that the new corner brackets are rubbish, they did not have the correct angle or twist compared to the originals. Hence like you I drilled out the rusted screws, retapped and reused them, the new ones still on my shelf.

These wrong angles will cause stress. Also the screws may be slightly too long, I seem to remember taking the tip off on the grinding wheel, this tip could cause a stress point on the edge of the glass, even though this is not where your crack is??? Are there any other screws holding the uprights near the crack position?.

regards Andy

 

[red57]

I tend to think it is more likely caused by a very small chip or scratch at the very edge of the glass causing a stress riser. Might have been so small it wasn't noticeable when you installed it.

My reasoning is that I run a 100 windshield and they flex quite a bit when you raise and lower them so I don't think mis-allignment of the stanchions would be likely culprit unless it was way off.

I cracked an ElCamino windshield once by taking the SS trim piece off with a metal tool that put a very small chip in the edge of the glass - did't think it would be problem (wasn't visible with the trim back on) but when I first drove it out of the garage it cracked and the crack started at that small chip.

Like others have said, clean and examine all rubber and the edge of the new glass for any grit/chips/etc. You certainly have my sympathy, I have replaced 3 and it really is one of my least favorite things to do to a Healey.

Good luck
Dave

 

[tahoe healey]

You may be able to see the stress on the glass using polarized glasses. Stress patterns show up if you put crossed polarized lenses (two pair of sunglasses at 90 degrees) on either side of the windscreen and move them around the glass to frame edge of the windscreen. A dark field will show up if the glass is under stress and show you exactly where it is likely to crack.

 

[TimK]

Thanks, Tahoe, that's a good tip I'll use, when I install a new windshield.

 

[daily]

howdy,
i cracked 3 of em in my bn4.
went round n round with moss motors.
they eventually found new source, the ones i bought from them had a flaw where the glass was machined [at the four corners where they were fly cut to accomidate the corner brackets]
there where tiny spider fractures in the glass, that over time
[6mos]just took off
with respect 59er