Removing Undercoating but Not Paint

[Shelby_r_b]

I've been doing some research online to find the best way to remove undercoating from a car, but not disturb the paint underneath.  Has anyone had experience with this?

I have a car that had some of the original pinkish red oxide poking though a small area on the belly of the car (that particular area looked wet from oil or something - either way, the car hasn't been running for over 4 years).  I took a rag and some simple wheel cleaner (nothing too strong at all), and the undercoating came off really easy!  However, the dry areas wouldn't budge with the same cleaner.

I'd like to remove the undercoating, but not disturb the pain underneath, as it looks original to the car.  Thoughts?

Thanks!

[JD]

Liquid Nitrogen works...pop's-off with a tap of a rubber mallet.  (need to have a source - helps if you know engineers at a major tire company ;-)  )

[Bob Gaines]

,kerosene . I applied with a garden insecticide hand pump sprayer. Work with delron or equal hard plastic putty knives. You have to be careful of course because it is flammable. spray let set and soften. Scrap until  the soft is gone . Spray again and repeat. Long and tedious. That is the way I did it. Thank God I haven't had to do it often.

[Greg]

A heat gun or (careful) use a propane torch also works and you don't have as much clean up of the oil.

[papa scoops]

BE AWARE! MOST OF THE OLD UNERCOATING THAT WAS USED FOR SOUND DEADNING CONTAINS ASBESTOS! just a warning. phred

[sg66]

BraKleen (green cans) or similar from Autzone and scotch bright pads.

Although I didn't try, WD-40 is great for dissolving adhesives and may be similar to kerosene to soften undercoating before going at it with scotch brite and BraKleen.

[Bob Gaines]

BraKleen (green cans) or similar from Autzone and scotch bright pads.

Although I didn't try, WD-40 is great for dissolving adhesives and may be similar to kerosene to soften undercoating before going at it with scotch brite and BraKleen.

The OP doesn't want to remove any paint. I have seen WD 40 work wonders on similar materials but I have never tried WD40 on a big job because of the cost for large quantities.  A Scotch brite pad will remove paint as well as undercoating if it comes into contact with it.

[corbins]

try some wax and grease remover, soak it, then after 15/20 mins , soak it again. Old bath towel to rub it off.

[Greg]

BE AWARE! MOST OF THE OLD UNERCOATING THAT WAS USED FOR SOUND DEADNING CONTAINS ASBESTOS! just a warning. phred

Is there nothing they didn't put this stuff in.  Always wear a good proper fitting face mask for particulate matter (Not paper a paper filter) and take your cloths off outside with your mask still on (this is where a lot of folks mess up, as you breath in everything that was on your cloths and you take it in your house or garage), put them in a trash bag outside before you go in your house and immediately shower.  If you wear a Tyvek suit even better, just throw it away. 

You really can't be to careful.

[J_Speegle]

A Scotch brite pad will remove paint as well as undercoating if it comes into contact with it.

Especially the fine overspray when you go through a clean up like this. No matter how careful you are you will likely remove over 50% of the body color and pinch weld overspray and paint as you clean the surface leading you to less than original IMHO picture of what it originally was if you choose to reproduce or copy the details.

Just thought it should be mentioned

[NC TRACKRAT]

,kerosene . I applied with a garden insecticide hand pump sprayer. Work with delron or equal hard plastic putty knives. You have to be careful of course because it is flammable. spray let set and soften. Scrap until  the soft is gone . Spray again and repeat. Long and tedious. That is the way I did it. Thank God I haven't had to do it often.

+1  My wife and I have spent untold hours laying on our backs, scraping off undercoating on a number of concours-bound vehicles of various marques.  It's messy, it's tedious but it's effective.  Just be thankful they didn't use COSMOLINE like that used on the undersides of drivetrains on BMW's and Porsche's...that's a whole 'nother story!

[Don Johnston]

Cosmoline is a wax base petroleum based preservative that will come off with most tri-chlor based cleaners like red can CRC Brakleen (or similar).  Imperative to use proper charcoal filter breathing mask, rubber gloves (nitril and latex not good enough).

Asphalt based undercoating may or may not have asbestos.  It will remove with most solvents but will be gummy.  Protective gear as recommended with Tyvek cover up is really necessary. CRC green can Brakleen is alcohol based and may work but is weak and requires more effort.  Suggested freeze method worked for me.  I used cans of freeze spray (type for removing rusted bolts) and then Brakleen (red).  Did a soapy low pressure power wash.  Red oxide semed okay, but I decided to repaint the red oxide anyway.

[sg66]

A Scotch brite pad will remove paint as well as undercoating if it comes into contact with it.

Especially the fine overspray when you go through a clean up like this. No matter how careful you are you will likely remove over 50% of the body color and pinch weld overspray and paint as you clean the surface leading you to less than original IMHO picture of what it originally was if you choose to reproduce or copy the details.

Just thought it should be mentioned

Good point on the overspray!

Fine scotchbrite is what I've used in the past and wasn't coarse enough to remove or scratch the enamel. A towel will also wipe off most dissolved undercoating

[Bigblock]

Eastwood had stuff called 'Under gone' (close) and you would spray and it would get gooey. A delron scraper just pushed it off and I would do a final wipe with mineral or alcohol.  Used 7 cans on a 67 stang. But I don't see it now on Eastwood's site.

[BGlover67]

Eastwood had stuff called 'Under gone' (close) and you would spray and it would get gooey. A delron scraper just pushed it off and I would do a final wipe with mineral or alcohol.  Used 7 cans on a 67 stang. But I don't see it now on Eastwood's site.

https://www.jegs.com/i/Eastwood/352/31130Z/10002/-1