My 77's rear bumper has a gap of about 1/32 of an inch on the drivers side, tight on the passengers side and has two small gouges in it. One is about 3" long and 1/16" inch deep and other is smaller. Can I fix the sag? Is there a urethane repair I can do to fix the gouges? Was hoping to not have to repalce it. Thanks.

 

There are a good many products our their to fix your bumper. The easiest way to find the best one is to talk to you local body shop, they can point you at a product that works great for them.

I will tell you that it is possible even if you fix it, it could still sink and you will be back to square one. Just depends on how nice the car is and if you want to mess with a new bumper.

 

Yup, plain old plastic filler if it's not too deep will work just fine. There is a urethane repair kit. I forget who makes it or what it's called, but if you get it from the body supply place, it'll come in a green and white tube. After you mix the two part epoxy it smells like feet. It works pretty good. The '79 Camaro had a corner ripped out of it and you would never tell, now. If the bumper cover has a sag in it, loosen it up at the mounting points and adjust it back into place. If it's stubborn, use a heat gun to soften it up a bit and work it back into shape. Good luck!

 

This stuff works great. I've patched tears and filled in divots with this stuff.
Here's what you want:

 

if you plan on repainting the car/etc... just replace it.... its old and would crumble/crack

 

trying to fix cracked urethane is temperamental, it will often re crack along the repair. it is often worth it to just replace the part.

 

Do your self a favor, and price out a new fiberglass bumper- call Vanacor Corvettes. Then decide to fix or replace.

 

http://www.vetteweb.com/tech/vemp_08...air/index.html

 

If you don't plan on repainting the car, just want to fix the gouges, I'd apply some urethane epoxy primer to the gouges with a small brush. A couple coats. Then, once that cures thoroughly, gently sand it with some 120 grit. You just want to create some scratches for the filler to 'bite' onto. Filler won't stick well to the urethane, but the primer will ...and the filler will adhere well to the primer. After sanding, apply a thin layer of 2-part glazing putty, or just plain bondo over the gouges. Once cured, just wetsand the bondo flat with 220, then 320 wrapped around a paint stick. I say wetsand because you can get a smoother finish w/o roughing up the areas adjacent to the gouges. Then, put a halogen shop light near the filler for 20 min or so to heat up evaporate the water out of the filler, then re-prime, wetsand smooth again and re-finish as per necessary. Those old bumpers aren't very flexible by now and bondo does flex plenty at that thin of an application. It will work fine. It's a lot more work to use urethane repair.

Noe, if you have your bumper stripped bare and you are doing a total repaint, it might be worth considering the bumper repair. But the repair kits aren't cheap and once it hardens, it's not that easy to sand smooth. You'll end up using some sort of filler (or heavy primer) on it anyway to make look good. Me, I'd prime up and use filler if it's really thin.

Where you have the gap, what happened to mine was all the holes on the back side (in the fiberglass) were broken out ...probably from some dufas' sitting on the tail section. I had to seriously grind almost every hole and re-glass with fiberglass cloth and matt, then re-drill and file the holes out. Took a while, but is nice and strong now. But that is one reason my bumper cover didn't fit well. Plus, I think it shrunk ..got hard with age. I replaced it.

Replacing the bumper covers aren't necessarily a easy fix. I spent at least 2-3 days getting my rear bumper cover (flex-fit) to fit 'perfectly'. I had to cut and re-glass a couple areas, even though it was new. The front side I bought a new Ecklers urethane bumper cover and it needed to be trimmed and I had to fit it to the front fender (bondo out the fender to fit the cover) and that took time too. Depends on how picky you are. These cars were practically hand fit on the assembly line and the fit/finish was horrible in their day. That's why they went to the one-piece front end and drastically cut down on the panels needed to make the C4's so it would reduce fit issues.

As for the comment that the urethane repair kits don't work well, I've fixed several cracked bumper covers and never had one break ...or material shrink. One was my caddy bumper cover about 5 years ago after a deer hit. Fixed it in several places where it was cracked and it still looks great even to this day. You'd never be able to tell. I generally use DuraMix (a 3M company) repair kits.

But for a gouge, I'd use filler.

 

Roger Brunelle, whose Bruno's Corvette Service was THE fiberglass body shop in L.A. for 40 years, made and sold fiberglass front and rear Corvette bumper covers for a fraction of the cost of OE flexis.

He'd tell customers with bashed noses "Your bumper was designed to survive a 2 1/2 mph collision with no damage. This mess is the result of a faster hit. If you can guarantee you'll never hit or be hit going any faster, the factory part is the way to go. But for most people driving in the real world, it's cheaper to replace and paint one of these fiberglass units as needed."

And using the same paint as on the body made for a perfect, lasting color match.