I have some rust in my wheel well and I'm looking for suggestions on removing the black rubberized coating that GM put in there. The rust is located in the area that the ECM is in. This must be a common spot for water to get trapped. I can put my finger through the hole and peek through where the heater box is.

 

Try gasoline,I think that would work the best.

 

Remove the ECM and other stuff that heat would harm, get a torch and a metal paint scraper. Heat the area with the torch, then scrape the undercoating off. It comes off really fast. Then use a wire wheel to finish cleaning it up. Cut out rust and weld in patch panel.

 

A wire wheel works fine by itself. It's really messy but you don't worry about catching something important on fire. PPE is recommended.

 

All th wire wheel is doing is melting the coating and flinging small rubberized sticky ***** all over the place. Im going to get a scraper and use a slight amount of heat and peel it off that way. I am also trying to remove the dynamatting from the floor which is even worse then the OEM coating in the wells. The adhesive just wont budge!!! The only thing that breaks it down is acetone!

 

I have warmed up the putty knife and used that. Of coarse you must keep a torch close by to keep it warm.

 

I used a grinder to clean off a 8 inch by 8 inch area where I wanted to put a weld patch over a hole in the rear fender well. worked great just made a mess all over the floor ans smelled like I was line locking the car lol but took only a few seconds.