Removing Dealer Undercoating

[Daniel S.]

Hi Gents,

What is the best way to remove dealer undercoating from the belly side of a midyear Corvette? The car in question is a Bowtie candidate and requires very little fundamental cleaning to bring it back from years of enjoyed use. I would appreciate if you could suggest a process that will not disturb the originality of the belly of the car nor be harmful to me (like using mineral spirits).

Many thanks,
Dan

[Russ S.]

Re: Removing Dealer Undercoating

A heat gun and a plastic scraper works well. After that I used lacquer thinner and many rags. The lacquer thinner doesn't appear to harm grease marks but you may choose to use something milder such as the mineral spirits.

[Jeff J.]

Re: Removing Dealer Undercoating

I had to do the same thing a few years ago on my '66. A previous owner had applied undercoating in an attempt to quiet down the interior noise.

I used a heat gun and a 1-1/2" to 2" metal putty knife. To prevent the metal putty knife from gouging or scratching the fiberglas, I used my grinder to make the corners round and I slightly sharpened the knife along one edge to make it work like a chisel. I set the heat gun to about 7 on a 10 point scale and heated small sections at a time gradually by waving the gun over a small area to make sure I didn't damage the fiberglas (be extra careful on/around the seat/belt support plates-I slightly scratched one of mine). Once the small area of undercoating was adequately heated, scraping went quickly but the heating process took the longest since I was being extra careful not to overheat the surface. I then used mineral spirits from a spray bottle and a rag to put a final clean on the fiberglas after several "small" areas were scraped clean.

For safety reasons, I prefer mineral spirits as a cleaning solvent since its flash point is greater than 100F (which means it won't generate any flammable vapors below the flash point). I believe the flash point of most laquer thinners is ~20F (which means it is generating flammable vapors at most ambient temps) which could pose a fire hazard; especially if you are using a heat gun in the area. Other popular solvents also have ambient or lower flash points so be careful.

[Dave S.]

Re: Removing Dealer Undercoating

The archives has all you need to know on this subject. Its a nasty job. Good luck w/ it.

[Keith L.]

Re: Removing Dealer Undercoating

My 72 has undercoating that may be dealer applied or owner applied. It is thin and I can see the thicker Factory under it. Is there a process that will take the thinner undercoat off and not dissolve the factory stuff. I thought maybe factory stuff would be more resistant to disolving maybe??

[Les G.]

Re: Removing Dealer Undercoating

I have used a Hot Water/ Steam Pressure Washer it works great but it creates a mess on the driveway. I found it the easiest way. I did my spare tire tub off the car, but taking it off the underside fiberglass is a little bit more difficult as it is hard to see what you are doing unless you can get the car up real high and were a rain suit.

[Ron G.]

Re: Removing Dealer Undercoating

I have done this several times with more than just satisfactory results by using lacquer thinner and removing it in layers as not to damage the underbody. My contact info is on my profile if you would like more detailed instructions of how to do this.

[Tom R.]

Re: Removing Dealer Undercoating

I also used some lacquer thinner blended with a little toluene which allows the thinner to cut while reducing the flash point (I think that's the stuff from Lowe's the paint center guy suggested). Smells pretty volatile and it is. But works really well. I have a four post lift which made it a whole lot easier. Spread lots of newspaper on the floor and change often during the scraping. I had all the neighbors saving their newspapers for a week. Be prepared to be under there for a minimum of the better part of a week at six hours a day.

I kept the garage door opened with a heavy duty floor fan from Costco.com aimed at me which cleared any condensing vapors while making it relatively easy to breathe without a respirator on. And don't forget the protective eyewear. I used the method of soaking a shop rag with thinner and applying it to the undercoat with a scrubbing motion then following with a scraper. A lot of the time that took most of it off and then following with a new towel with thinner to remove residue. Kind of like using a progressively cleaner sponge when grouting tile. Did areas of about 2-feet square at a time. Underside of the 63 looks almost new still. Even discovered the build number in crayon under the passenger footbox put there on the assembly line on my 13th birthday in 1962. Nice!!

[Michael F.]

Re: Removing Dealer Undercoating

If the OP is bothered by mineral spirits? Tolulene and thinners will be even more of a vapor issue. As mentioned above it's a messy job.

I use a low flash all purpose petroleum solvent and a hot water pressure washer. With repeated applications. Best done over a grease or wash pit.

Let's hope it's not one of those Zeibart tar jobs.

[Jaime G.]

Re: Removing Dealer Undercoating

Hi Dan, I have used lacquer thinner and it works well but it is a long and messy job. Lots of protection gear must be worn. Call Ron Goduti.
Follow his lead. He is a great guy. Best to your brother and your dad.

[Dan P.]

Re: Removing Dealer Undercoating

put some diesel fuel in a garden spayer. Soak the undercoating every day for a week or so .Remember let it soak. Comes right off.

[Kevin G.]

Re: Removing Dealer Undercoating

Don't these thinners or spirits remove the "paint" from the frame? Using Simple Green (diluted 50/50), I accidentally removed an area of paint from the frame! Safe on the fiberglass underbody but not on the thin asphalt (?) based paint on the frame.

Regards,