I cleaned the fairly thick factory tar like undercoating from my 66 Galaxie with a cold water pressure washer.
No soap either.
Hate Honda's?
That little 13 horse Honda driving a nasty 4000 PSI pressure washer, peeled the undercoating off like you wouldn't believe.
Honda ran like a champ the whole time.
Used a narrow jet on the wand, I think 10 or 15 degree?
All that was left was a "very" thin film of goo that wiped off easy with some rags and varsol.
Left the bottom spotless.
I got a little wet from the water, but it was a walk in the park compared to my buddy that used a propane torch and a scraper on his car.
I read about this method years ago in HotRod magazine.
I think the article was by Frieburger.
Maybe this will help someone?
Just don't point the nozzle at any paint you care about. It will rip it off before you can blink.
Sorry, I didn't take any good close pics of the bottom after it was done,
but I can assure it was clean!
You can kinda see some of the clean spots in the pics,
and the goo on the concrete pad that used to be on the car.
