I'm redoing my car (my first time with real bodywork) and am trying to figure out why my three weeks of meticulous filler work on my Camaro suddenly seemed to disintigrate from underneath the primer.

I used laquer-based spot filler/glaze over Duraglass, and then Primed over it with 2k Urethane Primer. The car looked smooth and ready for topcoat for 24 hours or so. By the next day, it suddenly looked like I had forgotten to use filler in some pitted areas, and in others looked like I had never tried to sand the filler level before priming the car. I came to the conclusion that the spot filler was disintigrating somehow, and some guys at Napa told me that yes, using Urethane over Laquer could produce that result.

So now I wonder what I should do. Is the Urethane primer going to keep reacting with the spot filler if I leave it, or will it stop at a point? I have polyurethane filler now, and I'm wondering if I can get away with just smoothing over the primer where it needs it, or if I'll have to remove all of the laquer filler to prevent any more flaws from marring the surface.

Has anyone else ever made my mistake? What did you do to fix it? Are there any tricks that work to avoid having to strip it back down to bare metal?

 

It is never a good idea to mix an old school 1K product with a new generation 2K product.
You are talking two different substrates. (a thermo-set product over a thermo-plastic product). Unfortunately the thermoplastic keeps moving under the urethane as tmperature and humidity change.
The best, although not good news for you, is to get rid of all the spot putty. If you know all the areas you used it, that'd be great,
I kinda gotta think that you'd miss some though, unless your bodywork wasn't that extensive.
Remember to block sand the car before you get ready to paint. (you may also be seeing some of the shrinkage in the bodywork areas that will show your sand scratches from the repair material.)

 

I agree with Kevin G., the best (and unfortunately ONLY) way to achieve any sort of respectable finish at this point would be to sand down to bare metal and start over again.
Old school products and 'New Generation' products aren't compatible... sort of like spraying laquer over enamel... won't work out.
Ever try to super-glue plastic parts back together ? The same sort of reaction is taking place here... chemically, it's not going to fly.

 

Ahhhh.....okay, I guess I'm going to have to break the sander back out and go to town. The bodywork was pretty extensive over the rear wheels; the previous owner of the car didn't see anything wrong with driving it through a few NYS winters and never washing it. No holes, but the rust is in the metal now and I will have to weld in some new pieces in another couple of years when I can afford it, if I don't want the car to keep rusting through the paint ever couple years. Behind the rear wheels was real bad. Good news is that I don't have to go down too far before I hit the duraglass. But over the wheels and around the fuel filler flap are going to be a pain.

Thanks for the info, man.