I have an old ’57 Dodge which still has the original undercoating from the factory. I believe it is the old ‘asphaltic’, petroleum based undercoating…it dissolves when you spray WD40 on it (but not without a lot of scrubbing.)
I blasted (sandblaster attachment on a pressure washer) the entire frame and underbody of the car, which removed maybe 1/4 of the existing undercoating. The rest of it sticks tenaciously to the floor pan and does not come off easy at all (especially working upside down.) I figure it’s been there for 54 years and did it’s job, so I’m going to leave it.
HOWEVER, I do still need to go over the bottom of the car with something to get the spots where it peeled off (mostly due to engine oil, grease, etc.) And I would prefer to go over the entire bottom with something to ‘freshen it up’ and make it look better.
So after all that ;), what undercoating can I use over newly bare spots, but is also still compatible with the existing asphaltic undercoating?
I would prefer to use a polyurethane bedliner like the Gator Guard. Second place would be rubberized undercoating. And only as a last resort do I want to have to re-do it in the original asphaltic based undercoating (which I can still find online…I thought they didn’t even make that stuff anymore.)