Hairline crack on thermostat housing.

[Shelbydaytona91]

When reassembling the thermostat housing pieces, I noticed a hairline crack as I was tightening the heater hose threaded piece to the bottom of the head. The crack almost invisible but spreads a tiny bit as the adapter is tightened on to a barely visible hairline crack. It seems the crack runs up the side and goes all the way through to the threads on the other side. Haven't started it yet so I don't know if it'll even leak or how much, but my bet is that it will. I'm thinking of trying some Permatex 5 Minute Aluminum Epoxy Stick after I reinstall the threaded heater hose adapter, but I thought I'd see if anyone else has some recommendations before I goop this thing up.

[turbovanman²]

JB weld etc.

[Dusty_Duster]

I think one of our vendors sells brand new billet thermostat housings in a few different colors. I think they're supposed to seal better, too.

[Shelbydaytona91]

I think one of our vendors sells brand new billet thermostat housings in a few different colors. I think they're supposed to seal better, too.

I wish it was that, but its actually the section that's attached to block

[4 l-bodies]

Sorry to tell you this, but you are going to have a very difficult time getting a NPT thread to seal without taking the head off and welding. As you tighten the 3/4" NPT water nipple fitting, it's just going to open the crack up further. Then it will open even further when the head heats up. Might try some epoxy in the crack and also on the threads and barely tighten the NPT fitting into the block. Can't hurt to try, you know what the alternatives are.
Good luck,
Todd