This afternoon I spent some time removing the last of the tar undercoating from the body panels. The hood had some undercoating on its inside, presumably to protect the topcoat of paint from the engine compartment heat and to keep the engine noise down.
The hood I worked on (red) is the original hood that came with the car. I previously purchased a good-condition (white) hood that I was going to use as a replacement because of some damage to the original. However, I have since revised my thinking and intend to use the original hood because I think I can repair it and it is a “sure thing” in terms of fitting properly.
I removed the tar undercoating by heating and scraping it off and then using a solvent to remove any remaining tar coating the metal. I began in the lower left corner of the hood. I used my heat gun, applying it for around ten seconds about two inches from the surface, then using a small metal scraper to get down to the metal.
The coating came off pretty quickly. I moved up the left side and removed all the coating. In the picture below, right, I can distinctly see the image of Darth Vader in the lower portion of the remaining undercoating (right side, not yet scraped).
I scraped the other half of the hood and sprayed on the De-Solv-It solvent I have been using to clear off the residual tar.
Then I scrubbed the metal with my stripping brush and wiped away the tar residue. The solvent was very effective.