Roof cracking and crazing, A hand sized web of cracks on the roof Options

[z28barnett]

I am getting a hand sized web of what look like fine white cracks on the roof of my Black '95 Z28.

I think it may be more than just problems with the paint. I realize that the roof is SMC.

Has anyone else seen this before, or have a method to repair the roof panel?

A search on roof cracking didn't find anything on this board.

Thanks

Z28

[Formula WS6]

that sucks. if im not mistaken i think that whole top panel can be removed and replaced. might wont to look into info on ttops conversion see what people do to remove the panel

[Tony99SS]

Of the three fourth gens I own or have owned, one of them developed a few bubbles beneath the paint. My 99 SS has a handful of match-head sized bubbles scattered around the roof panel. The body man says the panel will need to be taken down to bare plastic to correct.

Tony

[pknowles]

I know you have a 4th gen, but every 3rd gen that I seen that has been raced for any real length of time has cracks in the roof. If it's on a metal part of the roof you can get to the back side of the crack and weld along the crack. Most of the time this bubble your paint real bad in that area, but that is the only way to "fix" a crack. If you do weld it, concentrate on the tip of the crack and where it started, the middle is less important.

[z28barnett]

Thanks for the replys.

I did a little more checking on what SMC is. It can be treated like fiber glass.

Since this appears to be surface cracking.

I would think that grinding the area down and applying some fiberglass vail and resin followed by a thin coat of bondo would be a sutiable repair.

The fiberglass should stop the cracks from showing through and bondo would give a smooth surface for painting. At least until the bondo shrinks.

On the 4th gen, the whole roof is SMC the metal is under that and the plastic pannel is attached with a urethane adhesive. So as far as I know the metal is fine and welding is not needed. You are right that the crack tips are the critical area. This is true even in plastic.

Sound resonable to you guys?

Z28

[z28barnett]

I love this, I took a closer look at the roof, cracking is over the entire roof.

It would likely be easier to replace the roof panel than fiberglass the entire roof.

I saw a post on another board that there was a TSB on this problem. That there was a reaction from the glue used to bond the panels.

Anyone heard of this?

Thanks

Z28

[DryStout]

I saw a post on another board that there was a TSB on this problem.  That there was a reaction from the glue used to bond the panels..


Anyone heard of this?

I first read it in a detailing section. Specifically on ls1.com.

I think the TSB states replacing the panel.

[Formula WS6]

never heard of it til now. the dealership will know and should tell you though. id look into replacing the whole top personally even if there is not a TSB on it.

[z28barnett]

never heard of it til now. the dealership will know and should tell you though. id look into replacing the whole top personally even if there is not a TSB on it.

The labor of fixing the whole top might make it more prudent to replace it, good advice. The roof panel is around $450.00 with shipping.

No point in getting a paint job with this condition in the roof, cracks would just come right through it.

I found the TSB but I haven't been able to get the full text of it yet. Just the title, I am not sure their website is working right could not down load it. They want some research fee, odd.

Supposed to affect 1999 up cars the worst. Can cause paint bubbles ect, they used the wrong adhesive on some of the cars and changed roof suppliers bad combo.

I don't think they will help me, but who knows. This should not be happening but the car is 10 years old.

Z28

[rmackintosh]

can you attach some pics? I can't believe that it is anything MORE than a paint failure.....hard to believe that that peice would crack itself....if so, paint is EASY...

[z28barnett]

can you attach some pics? I can't believe that it is anything MORE than a paint failure.....hard to believe that that peice would crack itself....if so, paint is EASY...

I would like to think it was only paint.

You can catch your fingernails in the cracks and in a few places a small piece is chipped out.

It isn't like the panel is split and will leak, the checking is on the surface. This is typical of old fiberglass, to get a smooth surface the gel coat doesn't have any fiber reinforcement. So the surface can crack, but the fibers in the lower layers stop the progress. SMC will likely act the same way.

I am not sure how thick the clear coat is. I could send you some pictures via email but I don't have a way to host them.

There is also at least one crack in the bottom edge of the hatch also.

Z28

[z28barnett]

I sent you a photo by email.

Could be in the clear coat, seems a little too deep.

I guess sandpaper will tell the tale. If I can sand it out before I take out the black, it would have to be the clear coat.

Z28

[rmackintosh]

...yeah....its gotta be fixed somehow anyway, so you might as well sand it...I think you are correct on the upper layers checking vs. anything structural....

...but like I said in the email....I would go to a GOOD bodyshop...ask them thier oppinion, how they would repair it, and get an estimate....then do it yourself....

[z28barnett]

It could be the paint, I have never worked with the clear coat before.

Sanding will identify the problem for sure, I guess I can't make it look much worse.

Going to replace the hood due to rust.

So I should get the whole car painted.

I have the spray setup, but not much room to work in.

I might do the prep work and get a shop to spray the top coat.

I don't know about a good body shop, I talked to a few around here they want about $1500.00 to paint the car. That was before this started on the roof. You tend to find the good shops by getting ripped off by the bad ones. There are only two shops in town here and only one has a real spray booth.

This will not be a scuff it and go paint job. Has to be sanded right or it will be a waste. Hard to trust a shop to do lots of difficult hand work that will be covered up. They may try to cut corners.

Thanks for the info

Z28