This weekend I spent several hours removing the tar undercoating from the underside of the body. The tar coating was originally applied to the bare metal; I am removing it to see if/how much rust damage there is. The coating serves to cushion the body from stones and other road items that may contact the metal. It also insulates the inside of the car from heat and noise. For this reason I will most likely replace the coating with a modern version after treating any rust and applying a rust preventative to the sheet metal. But first I had to get down to the bare metal.
To remove the coating I used my heat gun and a metal scraper to do most of the work. On my scraping hand I learned to wear a thick work glove to protect my skin from molten tar. This is not particularly difficult physical work, but it is tedious and takes time and patience. Anyway, after spending several hours on it I am probably around halfway done.
I started with the areas underneath the front fenders, which were coated in the material. I applied my heat gun a couple of inches from the surface, allowing around ten seconds for the material to soften. Then I scraped down to the metal.
The very front end of the rocker panel (also covered by the front fenders) had a thick coating on it as well, where there was no rust. I scraped it off in a similar manner. So far this area, along with the lower edges of the fenders, has been the most rusty on the car.
Next I moved on to the outside of the engine bay area. More heating, more scraping.
Here are some shots of the under-fender area after the bulk of the coating was removed. There remained some tar residue on the bare metal, which I will address later.
Next I addressed the lower portion of the firewall opposite of the footwells. More heat.
More scraping, and the material came off.
Then I moved under the body, starting on the driver's side.
First I cleaned the inside of the rocker panel up the length of the car, then I moved up the underside of the body. I found it easier to scrape front-to-back over the ridges in the metal in order to more effectively remove the coating from the elevated and recessed areas.
Here is how it looked after I completed the passenger side, leaving only the transmission tunnel coated.
Next I went to work on the transmission tunnel. The odd shapes and reinforcement brackets in the tunnel made it difficult to scrape, but eventually I finished it.
After spending around five hours of total work time, working intermittently, I had the front portion of the tub complete. I have become proficient at perching underneath the body and reaching upwards with the heat gun in one and and the scraper in the other.
The rear quarters, trunk area, and wheel wells remain. They will be tricky because, unlike the front end, they consist of many small angular surfaces which are harder to clean-up than large, relatively flat ones.
