RQ Jay

I am currently underway in redoing the back half of my 1985 Trans Am.
The rear wheel wells undercoating look to be in okay condition with a bit of cracking and chipping in the coating that I would like to repair/recover.
I know that 3M makes a rubberized coating I have used in the past, but that coating never really hardens as well as the factory stuff is.

I would be open to others experience on this if you have actually replaced the coating...
Thanks

Drew

iTrader: (58)

Is the coating cracking, or the seam sealer underneath? If the seam sealer is cracking, and it probably is, you'll want to replace it first, then undercoat.

RQ Jay

Drew- While I do not have the ability to get a picture right now, I do not believe the seam sealer has any issue. The cracking is only in a few spots and none look really deep.

Drew

iTrader: (58)

The actual coating is pretty thin, it wears away over time, chips or scrapes off, but I've never seen it crack. The sealer on the other hand, is much thicker since it fills the gaps between the panels to prevent water getting in the joints. The sealer is old, dried out, it's started shrinking, pulling away and cracking. It's important to keep an eye on the sealer, because that is where these cars rust.

Check out the 3M website. They have many coatings for rock guard, undercoating, sound deadening, etc. Several are probably suitable replacements for whatever GM used. I haven't gotten around to reapplying the coating, only have spent a bunch of hours removing it. I'm curious to see what other people have used.

RQ Jay

Drew -
Upon further review I believe you are correct..
The cracking was/is very fine but it does follow a ling line around the top of the wheel well.
I took a small screwdriver and chipped some out to find that directly below that crack line is an area that the inner and outer fender Sheet metal meet together.
I will strip and clean everything with a 4" grinder with a wire wheel to remove all loose dirt and liner, re-apply a new seam sealer and then apply a coating.
Looks like I have something to do Saturday morning...

Drew

iTrader: (58)

Having spent several evenings this last summer under the project car, scrubbing and dissolving undercoating, etc... I'd make this suggestion - Don't get carried away. A grinder may or may not strip away the... uh... stuff? but it will chew up the factory e-coat underneath. You may want to keep that tough factory protection, and save a lot of work.

If you're just looking to do a quick fix, I'd probably use a stiff putty knife, or an old flat screwdriver, and carefully chip away what is loose, only in the area of the seams. A little heat from a heat gun can help soften the gunk and make it easier to remove. Clean with your choice of solvents, and apply fresh sealer then fresh undercoat. That way you're not removing the protection of the OE e-coat, and you're not getting into a huge mess of cleaning away the old products.

RQ Jay

Drew -
I appreciate the guidance, will likely proceed that way...
Thanks

roadthrills

I use the scraper and screwdriver method, followed by a wire wheel. My local auto body supply has about 5 different types of undercoating. Smooth, bumpy, glossy, flat,etc.