Does anyone know if you can repair a crack down the center in the front air dam on the blazer xtreme?

 

it can be done but they always crack again.

Best way is a product called fusor thats designed to be a plastic repair epoxy.

 

I've done several bumper covers with flex filler. Back up the crack with thin sheet metal. Alum siding piece about perfect. Bonding that with acrylic - not silicone- caulk cant hurt

Put countersink type screws from front through the backer about every 1 1/2". groove the crack, then feather that out about another 3/4" on each side. Filler, then sand and apply surface fill stuff.
Most you'll get over time is a hairline crack.