moondoggy200

Hello I have a 1974 vette it has a new 3 stage paint job, on the engine hood there is a 3 to 4 inch blister in the paint, when I bought the car 3 months ago I had the seller repaint the hood it came out perfect, but the same blister is just starting to reappear, and I just noticed the inside of hood is missing the insulator blanket that goes on the inside of hood ???? could the engine heat be causing the blister? what do you all think. I have ordered a new insulator blanket, thanks in advance for all input. Rich outttt.

Roco71

The cause could be from contaminants coming up from under the hood. Does your car have a/c? Sometimes oil from the a/c compressor will come up from underneath the hood. It does not have to be oil from the a/c compressor that just seems to be one of the more prominent causes.

Easy Mike

Normal underhood temperatures do not get high enough to blister paint from the underside. Corvette hood insulation is for sound deadening purposes, not heat protection.

AC clutch oil can seep through fiberglass over time. Is your paint blister over the AC compressor?

My first hunch is that something is in the fiberglass/primer/sealer causing the top coat to lift.

Roco71

The bad news there is nothing (that I know of) that will stop it. The hood may need replacing.

hugie82

I have a bubble from heat too. It only happens when I leave it in the sun on a hot day 90+ then it disappears when it cools off. I think moister gets under the gel coat and expanse when it gets hot...

Alan 71

Hi,
I think as others have said M200's problem sounds like a contamination problem; while h82's sounds like an adhesion problem.
Regards,
Alan

lvmyvt76

You can get an add on piece that bolts to the a/c compressor to help stop oil from getting on the underside of the hood.

moondoggy200

Hello again My 74 does have AC. its hooked up with fan belt but it doesn't come on, or run, if there was oil contaminants ? would I be able to see Ollie substance on inside of hood? I did have a big power steering leak for a week, thanks for your help.

Roco71

You might be able to see oil on the inside of the hood or it could have been cleaned off. I have seen contaminates come from tar based sound deadener the oil from the tar gets in the glass. Fiberglass is porous and absorbs things sort of like a sponge. Once in the glass its difficult if not impossible to get out of the fiberglass if it has started from underneath and worked its way to the top. Setting in the sun draws the contaminates to the surface. This is one of the reason many of us use epoxy primers to help seal the surface before painting. Where on the hood is the paint bubbling?

moondoggy200

Hi again the blister is just off center, favoring the driver side. I did have a power steering hose burst and leaked brake fluid ever-wear, if it is a dent repair that was poorly primed under the paint I know the seller and can get the hood grinded out and fixed, primed correctly it could be that the body shop took a short cut, thanks for your input. this is my first vette and I love it, just going to take some getting used to all the special insights to how they work, this web site is so valuable thanks again Rich outttt

Easy Mike

Yah, but it serves no purpose if the contamination has already taken place. By that time, the proverbial horse is already out of the barn.

myko

I have bubbles showing up on a few different panels so I hope someone here has some (any) ideas. It was out on a few 100+ days and developed some bubbles that split and contracted the clear coat but I am still concerned that thinner in the fiberglass is the underlying problem. I am waiting to see if anything else develops over the summer before I try to fix it. I was going to try sanding and spot repair myself - hey, it won't look any worse - before I do anything costly/drastic.

Does anyone have any suggestions? I'll try about anything before I replace that much fiberglass!