Why is my 3M fast and firm sealer cracking?

Put it on over fresh primer about three weeks ago and it is cracking. Why?

Not only are corner beads cracking but also edge seams where I forced it into a seam and wiped it clean.

The body was sandblasted and then epoxy primed. Sealer applied over primer. then left open to the air. The stuff under my floor that was painted the next day after the sealer was applied has not cracked. Do I need to wait and dig out all the sealer and apply it right before I paint??

Talked to a buddy of mine today and he just said its junk, and that everyplace he has ever used it cracked too. Says you are better off using body filler.

Anyone else had the same experience?

That's a good question, mine cracked too. I put mine on the night before I painted. It took a couple of months before I started to see the cracks through the paint.

David

Well body filler isn't the answer. That will crack. I use Transtar seam sealer with caulk gun and it works really well. It sets up really firm, but still rubber like.

Dont use the firm setting seem sealer. It will crack use the stuff that still stays a little flexable. The bronco chassis and body moves alot when on or off road. I used a NAPA brand seam sealer on my last project and it worked great no cracks so far and it has been in paint for over a month. And the NAPA stuff was only $12.00 a tube compaired to $20.00 a tube for the 3M stuff.

Fast and Firm is the crapiest junk out there.

Use a urethane sealer. It stays pliable and wont crack.

3M or Lord Fusor, we use them both at work.