In replacing my old, original wiper motor with a rebuild, I wanted to find a good, clean, secure, easy way to seal the interface between the motor and the external firewall. I would be that the new grommet on the inside firewall would do a good job of preventing leaks on its own. But I noticed that the original had what looked like a bunch of white caulking squirted around the area. To me it looked ugly, inconsistent, and not likely all that much help. It did, however, never leak.

After considering what I might use - such as caulk, silicone sealants of various sorts, and more - I decided to use plumber's putty. This stuff is pretty amazing. It is cheap, easy to use/apply, and I happened to have some in the shop - for a small job some time ago I had to buy a whole tub and there was plenty in like-new condition.

I rolled out a small log of the putty and covered the circumference of the hole in the firewall.



I carefully pressed the new motor into the hole/putty and was pleased with how the putty filled in and spread out under pressure.



As I tightened up the mounting bolts it just looked better and better to me.



And a nice seal seems to be there on all sides.



Of course, how it will eventually pan out - if it will stay dry inside for another 20 years - remains to be seen.

Cheers