I am currently restoring the original engine compartment wiring harness on my 73 camaro. At the firewall connection the terminals are filled with a brown gooey substance to keep out water. I need to reapply this protection as I have removed a lot of this stuff during cleaning. Although, I can not figure out what this stuff is. It is thicker that dielectric grease, is not undercoating, and does not appear to be seam sealer. Does anyone have any idea what this thick brown grease like substance is. HELP!