Underseal removal

[GaryF]

Hi All,

Just wondered if anyone had any good tips for removing old underseal from a car. I've seen suggestions that engine de-greaser is a good starting point. I dont have a pit or car lift so I'll be scrabbling about with the car on stands.
The car had a heavy coat of underseal when I bought it and I'm curious to see if there are any horrors lurking underneath

Thanks,
Gary

[Mike D]

The only tip I can give is to not remove it. It's a horrible nasty ordeal and any replacement rust proofing you can buy will not give you the protection of the original glop.

If you have a loosened area you can scrape it loose, clean with paint thinner or mineral spirits, wire brush it CLEAN and then respray with a treatment. You will NEVER get the adhesion and coverage to the old metal which was there when it was applied to new metal. Use a rag soaked in thinner or spirits to "blend" the new into the old. ANY place where you don't get the rust proofing to meld with the old will be a moisture entry point.

Degreaser won't cut it. You need something to "re-activate" the glop and that has to be a petroleum based product.

I can not stress enough as to how nasty of a job it is. Got any ex-girlfriends you don't get along with? Do it in their driveway.

[alabbasi]

thats one good way

[Benzcrusher]

Hit it with a cutting torch and it turns into a firey goo...

[senorunimog]

I am just finishing up a job much like what you are about to start. I have found that using a torch can be dangerous, I caught the inside of the car on fire and melted some of the wireharness going to the rear of the car...
Be careful with a torch

I have taken to using sharpened putty knives, and sharpened screwdrivers. Sharpen them frequently and it peels right off, somewhat tedious, but I think it's safer and somewhat less messy (well, less goopy anyway)

When you are looking for rusted places, look for cracks in the undercoating, especially any with rusty colors peeking through, it might be worth while to pressure wash the underside of the car before you start so you can see where the coating has failed.

Be advised, you are getting yourself into a HUGE job
Best of luck,
-Eric

[250 Coupe]

This stuff claims to work if you can leave an impression with your thumbnail.

Michael

[300SDog]

And this is all for exploratory purposes out of "curiosity?" Hell, it sounds like first step to making a basket case to me - kinda like tearing into a cylinder head and then leaving the parts scattered around.

If you really want to know what's happening underneath the undercoat then tap it with a rubber hammer instead.

[GaryF]

Thanks for the responses. The reason I started down this path is because rust is showing through in a few places. The car was reconditioned in the early 90's and has been reasonably well maintained but there's a niggling worry that the undercoat was simply put on top of rust, especially as it appeared to have been done shortly before I bought it.
I'd like to stick my head in the sand and hope for the best especially as its not a concourse car and its value doesnt justify having any major work done, but equally I'd like to know I'm not putting my family in avoidable danger every time they're in the car.
I'll cleanup and put rust converter on the bits I can see and try the rubber hammer test before getting to carried away.

[Nate]

they were undercoated from the factory...


An easier way to inspect the floors is by pulling up the carpets. Be warned, you CAN drive them FOREVER before they fall apart... Just get another set of floor mats
~Nate

[Tony H]

Try gently tapping a screwdriver into the suspect areas. if it is weak the screwdriver will go through. Just a quick test.
Tony

[mercmad6.3]

Gary ,Are you talking about bitumopus underseal,the black stuff that looks like tar?.
If so it should be removed with a propane torch by gently warming it,until it's soft then scraping it with a large spatular.be careful or you'll burn yourself if it gets too hot.
the residue will come off with turpentine.
The original undercoat is PVC and can only be bought from "Wurth".there are other products available but none are very good.Once the original undercoat cracks,rust will follow quickly.
I would only recomend doing this is you are intending to keep the car as it will take at least a day to each wheel house.The sills and floors take forever.
Ideally the car should be stripped to the shell and rotated on a rotisserie to get at the floors easier.