Heater core replacement
 

Hey guys I am working on restoring my under hood heater box and I had a question. I replaced the heater core but need to know what everyone uses to seal up the holes where the heater core nipples come thru the box. Anyone know? This is an old picture before restoration.

Re: Heater core replacement
 

Never mind. I just realized my gasket kit included seals for them.

Re: Heater core replacement
 

Dumb Dumb/Dum Dum or strip caulk. Available at hardware or automotive parts stores. Some electrical supply places carry it too. It is a clay like sealer that doesn't harden.

https://www.amazon.com/3M-08578-Blac...000PEZ1L4?th=1

LockDoc

Re: Heater core replacement
 

I used a thick bead of Black Silicone caulk
It filled the gap nicely and won’t harden and fall out

Re: Heater core replacement
 

I recently bought a box of 3M strip caulk from a local parts store. Not everyone carries it anymore but it's what I used to use 40 years ago. Wow. It's gotten expensive. $27 for one box and it was a pain to use. I won't buy that one again.

Re: Heater core replacement
 

I use the 3m black for everything like this much better than the grey string robe also by 3m .

The black is a butyl tape so it sticks well . To everything I even used it on all the bed seams on the stepside.