what's the best way to remove under coating

moparrodder · February 03, 2005, 11:12:02 PM

I'm rebuilding our 40 Plymouth 2dr and am going to take the body off the frame. About 20 some years ago I cleaned the underside of the body and sprayed 3M under coating on the underside of the body and since I will be changing the color a bit it needs to come off. Can it be sandblasted off or with a scraper and elbow grease? Bill

enjenjo · February 04, 2005, 12:01:02 AM

The best way I have found, is to let it get real cold in the shop, and remove it frozen with an air operated scraper. Sandblasting has a difficult time removing it.

58Apache · February 04, 2005, 12:28:29 AM

I don't know if there is a different formula now than then, or if having it sit for a long time makes a difference, but I have been putting 3M undercoating (rubberized) ON my car during my restore.

Recently I discovered by accident that brake cleaner melts this stuff right off almost.

I also had areas where there was something there, maybe undercoating, maybe road grime or old grease, but a wire wheel just seemed to spread it around.

I bought a wallpaper steamer and steamed it a little at a time while scraping immediately afterwards with a putty knife before it could get cold. Worked better than anything else I tried.

Steve

GPster · February 04, 2005, 07:26:01 AM

Somewhere in the archives (2 or 3 sites ago) somebody recommended oven cleaner. I'd try that before brake fluid. Brake fluid might work good but I'd be concerned about ever getting paint to stay. I put the oven cleaner (lye?) idea in my mind but have never used it, so it's un-tried by me. GPster

Roadstar · February 04, 2005, 08:22:29 AM

Depending how thick it is, one of the ways I have gotten factory undercoating off is to heat it with a propane torch,not too hot and use a scraper. then use wax and grease remover with a scotch bright pad and scrub it and follow with a rag with more wax and grease remover( Minerial spirits works good too) and wipe it clean.

DRD57 · February 04, 2005, 10:23:46 AM

Quote from: "moparrodder"I'm rebuilding our 40 Plymouth 2dr and am going to take the body off the frame. About 20 some years ago I cleaned the underside of the body and sprayed 3M under coating on the underside of the body and since I will be changing the color a bit it needs to come off. Can it be sandblasted off or with a scraper and elbow grease? Bill

I used a propane torch and a scraper and then finished it up with 3M clean & strip wheels. It's heap of work especially when you have several acres of floor.

Fat Cat · February 04, 2005, 10:54:06 AM

Quote from: "DRD57"I used a propane torch and a scraper and then finished it up with 3M clean & strip wheels. It's heap of work especially when you have several acres of floor.

Yea but we all know you are not sane to begin with

47wood · February 04, 2005, 11:48:21 AM

I've used a heat gun and scrapper. But if it isn't too thick I've had the best results with a wood chisel. For the final cleanup I use acetone. Either way it's a messy, thankless job. Cal

av8 · February 04, 2005, 12:22:33 PM

Frank is absolutely on target with the cold approach. Underseal remains in a plastic state almost indefinitely, which is why it's so good at hangin' on. Heat from torches or friction rejuvenate it, and while it can be removed this way, it's a tedious, time-consuming, and messy process as some have discovered. When frozen, the underseal loses much of its ability to adhere to the surface on which it's applied and can be easily chipped off.

There's an industrial/medical process that amounts to freeze-blasting that's gaining popularity and may be available to you locally. It's used to clean hospitals, food-processing equipment, restaurants, printing presses, etc., where chemicals, down-time, and mess can't be tolerated. We have such a service here, in Sonoma County that, among other things, is used to destroy bacteria in wine barrels and vats. I've seen it used to remove the undecoating from a restored '56 Chevy BelAir on which the original undercoating had been "repaired." It was scary watching the blast directed at the underside of beautifully painted fenders, but there was absolutely no harm done to any surface or finish. The underseal was removed with just a few hours work, swept up and discarded without leaving any film or residue anywhere. Very impressive process.

Here's a link to a manufacturer of cryogenic cleaning equipment. It might be a good place to start looking for a local source for the service.

http://www.cryogenesis-usa.com/

Handy Homeowners Tip of the Day: To quickly and easily remove asphalt or vinyl floor tiles, place pellets or shards of dry ice on a small section of tile to freeze the mastic bond. As it releases, usually signalled by a "popping" sound, broom the dry ice to another spot and remove the freed tile with a scraper.

And you thought this place was all about cars . . . .

moparrodder · February 05, 2005, 12:01:33 AM

Boy you guys are the best!!! Ask and ye shall recieve. I knew I would get the answer to my problem and answers I got!!! THANKS to all who replied. They were all good suggestions and I hope to put them to good use. A friend has a rotisserie that I can get to put the body on to flip it upside down and get to the bottom easier, but will be a little bit before I can get it. When I get the bottom cleaned I'll set it off to the side and put the frame on it to have it blasted and ready for the motor and tranny mounts installed and updates to the brakes. I'm going to check into the dry ice cleaning thing to see if there is someone close . Thanks again for the input!!!

Bill

Jim in Texas · February 05, 2005, 01:37:29 AM

Eastwood sells some undercoating remover; you're supposed to spray it on and after it loosens, spray a cleaner/ neutralizer on it and wipe it off.

It makes the biggest mess imaginable! That stuff runs off everywhere and will get on your lift, the floor, and on you!

The remover smells like turpentine and is sort of soapy, the neutralizer is nothing more than naptha.

It will do the job, but it's slow work, very messy and expensive!

I have stripped most of the bottom of my 57 T-Bird, and tried everything from the Eastwood stuff, oven cleaner (which didn't work well) naptha, a heat gun with a scraper, wire brushes on my drill, 3M stripper discs and still have the underside of one wheel well left to finish it out.

It's a tough and dirty job.

Eastwood shows a single or double row cup wire brush in this month's catalog that looks interesting. The #'s are 13367 a 4" double row brush for $34.99, and a 13369 2 3/4 single row brush for $19.99. I'm going to Harbor Freight and see what they have that might work (lots cheaper).

My thoughts are that you really need to be careful with spinning wire brushes, wear good eye protection, a mask to keep the undercoating dust out of your nose, long sleeves and gloves! Wire brushes tend to sling wire pieces! Be careful!

Good luck!

Jim