Undercoating and Rust inhibitors

You might look into using POR-15. I just finished my engine bay using it. Do a web search for info.

I used a heat gun (on low) and a putty knife. Working in small areas at a time until it became soft, then just scraped it all off. It took about a day, mainly because of my aching back. Other wise it should only a few hours. I took it off everywhere from the fire wall back. You can even use a little body filler to smooth over the spot welds before using the POR 15. Its great stuff and comes in colors for a super undercoat.

I've just finished this process, and what a pain. Is it worth it? Yes it is, however it is possibly one of the dirtiest jobs I have ever encountered working on an automobile. I initially used aircraft stripper to get the majority of the stuff off of the flat surfaces and then used a combination of heat gun/scraper and a wire brush on a 4" angle grinder. Total time to remove all of the undercoating was probably 10 to 15 hours. That includes about an hour to unstick that crap from my shoes, under my fingernails, etc. Just throw your clothes in the garbage. I finished the engine bay with Duplicolor Truck Bed Liner material on the advice of Tom Dupart. I am pleased with the result. Including the body work to remove the major dents and clean up the spot welds and actually spraying the bay, I probably have another 10 hours in the project for a total of 20 to 25 hours.

Thanks everyone. I think I'll try stripping it. The frame rails are covered in 30 years of oil and grease. I think it acted and rust protection :-)
I scraped some of the grim off the rails and exposed the original paint.

Alan

I have found that scraping it off after heating the undercoat from a heat a gun or even from a propane torch on a low flame held several inches away, (careful not to apply to much heat because of warping the sheet metal, also only use the torch in areas where fuel, oil or other flammable/combustables are not present, also you will need to have a fire extinguisher close at hand). To remove the very fine remants of the undercoating I sprayed a heavy coat of WD-40, letting it sit for a few minutes and it wipped right off with no hard rubbing required. Good luck it is a very long process but required for removing and repairing any rusted or otherwised damaged sheet metal.

Dear Alan
You my also want to try haveing someone plastic media blast it for you. I do this for a living and works great. A few things to think about. Is outside of car painted or are you working on that too. The Car can be done this way ( just makes it more of a challange). See if you can find a media blaster in your area and talk to them. This will save you alot of backbreaking work! Good luck. Tim

Tim,
My experience with media blasting the undercoating was not too successful. The tar is soft lessening the media's effectiveness. They shot the whole car with media but had to use sand in the engine compartment at low pressure.

With a unibody, the media makes a mess collecting in all of the rocker boxes and joints. Takes a lot of effort to remove the overage out of all of the blind holes.

My resto started with the scraping,followed by media blasting,only to find myself doing half the job.

I decided to take the whole car appart (one day) and have the whole body hot tanked!
Followed by a dip in a electrolitic derusting,then a dip in a zinc phosphate tank.

This cost about 2 grand canadian,but was THE best way of properly restoring the car.

The whole car got blasted with an etch primer,and the cavities were injected with por-15.

Unfortunately,it took me a couple of weeks to reasemble.

good luck!

Craneman.