How to Use Tar to Patch a Rotted Firewall

A hole in your car's fire wall presents more than noise problem: Fumes from the engine can hurt you. A quick and effective way to patch that hole involves the use of tar as a sealant and adhesive, but you cannot do it with tar alone. By utilizing sheet metal and a rivet gun, you can make a strong permanent repair, allowing you to ride in comfort and safety.

Instructions

1

Put on safety goggles. Move any carpet and felt that might be in the way inside the firewall. Widen the rotted or rusted out hole in the firewall by 1/2 inch all around with a nibbler snip.

2

Grind paint and leftover rust a half-inch around the widened hole, using an angle grinder, both inside and outside the firewall.

3

Wipe the ground out area on both sides with an alcohol-soaked paper towel.

4

Measure and cut a piece of aluminum sheet metal to fit over the hole with a half-inch overlap, using the nibbler.

5

Heat a half-pint of roof tar in a cast iron pot over a stove or burner. Apply melted tar to the outside overlapping half-inch of sheet metal and to the cleaned area on the firewall. Allow the tar to cool enough to make the tar tacky, then place the sheet metal over the hole, pressing down firmly on the contact area.

6

Allow the tar to set and harden overnight. Drill holes every 3 inches through where the aluminum overlaps the firewall, using a drill with a 1/8-inch bit.

7

Insert rivets through the drill holes and fasten them with a pop rivet handgun. Heat tar again and liberally cover the entire patch and surrounding overlap areas inside and out.