Removal of factory spray?

[Bird 426]

Yeah, salt and water can hide anywhere, undercoating or not. It's also somewhat of a sound deadener. Doubt most of us would drive our cars in that today! I don't even go out in the rain. You could just do the fenderwells if you didn't want to do the whole car.

 

[RT68440]

I had pretty good success with a heat gun and a chisel. I tried a scraper but it was too flimsy for me, so I used a chisel like a scraper and it worked out great.

 

[KohrtRacing]

Thanks to the group for the heat recommendation of heat gun and a putty knife worked really well. Two minutes of work.

 

[kiwigtx]

Not to hijack, but what is everyone going back with that looks close to oem?

This was used on my car -

(internet grab)

To finish underneath we sprayed a generous Matt Clear coating to make cleaning easier later on.

 

[1KoolBee]

Aircraft paint stripper melts it away. Scrape off goo, then pressure wash.

 

[ynst]

Nothing. It holds moisture. Moisture causes rust. It was an option on my year anyway.

It does if you spray it over dirt because the dirt will encapsulate the moisture like a sponge. That's why Rusty Jones and similar after-thought undercoatings never worked and, sometimes, even promoted rusting because they were sprayed OVER dirt, not paint.

If it is sprayed on over fresh paint there's no sponge-like dirt between it and the metal.

My GTX was factory undercoated (I ordered it that way) and I drove it all year long and that includes salty winters in Massachusetts from '68 to '72 and the undercoated parts never rusted. There was, however, surface rust on the sections that weren't undercoated.

Not all of the underside was undercoated.
Some portions were, intentionally, taped up to prevent undercoating from being applied. Driveshaft tunnels and areas where parts would bolted on further down the line are some of the locations.
The only places that were heavily undercoated were those that could be reached from the proximity of the rocker panels by the painters standing on the paint line as the painted body passed overhead on the conveyor. The inside edges of the sub-frames, for instance, weren't undercoated but undercoat over-spray was often found on the lower portions of the firewall and radiator core support.

When I repainted the car I used a shutz gun and sprayed shutz back onto the fresh paint just like the factory did.

 

[Mr. PNW]

Back in the 80-90s I used this gun to apply rubberized undercoating on Mopars. The local auto body supply store sold them. It’s designed to spray heavy coatings and has the rough look of the OEM undercoating.

Undercoating
3M™ Body Schutz™ applicator gun, part number 08997
https://www.3m.com/3M/en_US/p/d/b40069354/

It screws onto this product.

3M Body Schutz Rubberized Coating Black, 08864, 1 quart​

https://www.3m.com/3M/en_US/p/d/b40071599/

I didn’t exactly like the 3M coating that well. It stayed too pliable and took forever to dry. I imagine they have far better undercoatings now, possibly the Rustfre product mentioned would be a good candidate. I just cleaned out a few of the 3M containers to use with other products.

Stripping
What I really loved about this gun was not mentioned anywhere.
Whenever I used any kind of heavy paint stripper, no matter the application, it would always say to use a brush and apply a heavy coat WITHOUT going over it a second time while wet, so as not to break the vapor seal. That always left streaks of paint in some areas where the brush would knock it down no matter how careful you were. You know what I mean if you’ve ever stripped furniture. It always took two or three times in some areas to get it all off.

So I tried using my gun to spray the heavy stripper and because it went on like a heavy sheet, it came off the whole area in one coat.
The best stripper I found back then was Napa brand industrial airplane, but I recall the formula changed. Typical.

For stripping car paint and undercoating I would put it in the sun on a very hot day, spray on, and when the paint lifted, I used my water hose with a high pressure nozzle to wash it off. I did not have a pressure washer which would have worked better.
I could strip fenders, doors, hood and trunk lid, to bare metal, inside and out on a hot day without using much elbow grease.