Paint Cracks On Rear Hatch...

[Helldog]

Hey guys, I got a question about the rear hatch and my paint. When I first bought my 280z it was white and had pretty shitty paint job. One of the things I noticed was that the paint on the rear hatch had crackes everywhere. I figured it was the old paint but sure enough I think I was wrong. After about a year or something like that, I had my car custom painted, I'm sure it was 2001 Viper Yellow, and of course before the paint they sanded and everything. I also had them put on a body kit I bought from zcarparts.com. Well anyways everything's great and all but I just noticed about 2 months ago that the paint on the rear hatch was starting to crack just like it was when it was white. Now, 2 months later, it's close to being like it used to be when it was white and it kinda makes me mad to think that the money went to waste on the hatch. I think it happens because the hatch flexes but I don't really know anything about paint so maybe someone knows...??? How would you fix this problem? Can you put a re-inforcement bar on the inside of the hatch to keep it from flexing or is it just the blazing California sun hammering on my rear hatch??? help......

[LanceM]

More than likely it is fractures in the paint that go all the way down. With this being the second repaint that you know of the car is getting a pretty thick build of paint. If the car had been painted even one more time before that you have a paint build you can measure with a ruler and it's almost a for sure thing that the paint is going to crack.

With the cracks in the original paint it should have be sanded or stripped down to the metal or at least the first coat of primer. Just blocking it before the repaint may not have removed the cause of the defect only it's effect. Yiper Yellow should be easy to match, I would have the hatch stripped, checked to make sure there are no stress cracks (unlikely) in the metal and have it repainted.

[TomoHawk]

Mine has cracks just behind the quarter qindows, about the sail vents. I think they weren't there when I got the car a few years ago, but are now there.

No help or temporary fix is there?

thx

[LanceM]

No temporary fix here. This is a common problem especially with cars that have been driven hard. Body flex causes these cracks, and I believe it is in the lead filler that was used at the factory to fill the joint line where the roof and body were welded together. The only fix would be to grind down to the lead filler and reflow and refill it, then shape, blend and repaint. Lead is used because of the stress there, a plastic filler would have broken out completely long ago.

[EScanlon]

Helldog:

Are you sure the cracks in the paint are due to flexing and not CRAZING due to incompatible paint base? Post a picture of the cracks, a lot of times a poor base will result in the final paint job showing "cracks" when in reality it's crazing. Sounds similar, but the causes are completely different. Usually when you repaint a known crazed surface you sand down as much as possible and then paint with a primer sealer to prevent future crazing. Doesn't sound as if your painter applied sealer before repainting.

If you had your paint job done at a Custom Body Shop, they might guarantee their work. Worth checking into.

Tomohawk: As Lance mentioned those cracks are on the join line between the roof and the fenders.

That you are cracking the paint there points to a couple possible items. You might be flexing the body very hard. Whether by hard cornering, Auto-X, riding hard over bumps AND there's another part of your uni-body that has also been tweaked allowing that part of the car to twist more than usual.

The other is that when the car was last painted, or on one of the prior paint jobs, they uncovered the lead filler. Lead is used due to it's malleability (as Lance mentioned), what's not commonly known is that it doesn't like the standard primers used on cars. The primers will stick, but eventually they'll start to "dry" and cause the paint covering it to become brittle. That's when you get your cracks.

Lastly, it could be a combination of the two.

Enrique

[THE73Z]

Could be bondo cracks. Take a magnet and wrap it in a t-shirt then go over the hatch and the rest of the car for that matter. If the magnet sticks you've got steel, if it doesn't stick you've got body filler. I always do the magnet test before I buy a car... and I bring ramps, and I've even pulled valve covers off. I'd have it x-rayed if I could - .

Anyway, if you have bondo you might want to dig up your receipt for the paint job.

[Pennyman]

Are you sure the cracks in the paint are due to flexing and not CRAZING due to incompatible paint base?

That's what I thought at first. It's also called "checking" it has to do with a coat underneath the present one (previous paint job perhaps) which had chemicals which don't like the chemicals in the newer paint (different, non-compatible paint additives). My roof is doing it pretty bad. Sometimes a water-based sealer primer can be used to help stop it, but you'll have to get it at a body shop.

[EScanlon]

Pennyman: You're absolutely correct. The difference in name may be simply due to different teachers or ...? But the fix is still the same, sand, seal, re-paint. I've not used a water based sealer/primer so don't know about that.

I was taught to use a REDUCER based primer/sealer or EPOXY based as opposed to LACQUER to correct the problem. I've not had problems resurface afterward, even years later.

THE73Z: The magnet "trick" can be very deceiving. There are fillers with metallic content that will "fool" your magnet and you. Additionally, the magnet is effective only in determining whether there is a THICK layer of bondo. A thin layer won't be noticed at all unless you are using a magnetic meter of some sort, and then could be explained away as "thick paint".

2¢

Enrique