Aluminum Block Freeze Plugs - Leaking

[Bunkie314]

First go around was Liquid TFE, coolant ran out like the plug wasn't installed. Tried about every brand of thread sealant I could find. To many to even list.

I even tried PTFE tape, which is the only thread sealant I was able to seal a 4500 psig air storage system. Still leaked after a few heat cycles.

I have also dropped down to a 7 psi cap to lower system pressure with some better results.

Block threads are an NPT with some kind of straight thread machined steel plug, I wish is was a STOR Port. Not sure Brass would be a good alternative due to galling issues, I assume that all the aluminum blocks are using these. 100 to 150 delta T shouldn't be that significant in 1-1/2 inches to hold 7 psi (I'd rather run a 15 lb cap though). Tightening when hot might overstress after cool down, so I have not done that either.

Flyboy,

I looked at the Bars Stop leak but considered the copper coat might be a better alternative. As Tom stated some stop leaks have issues stopping more than just leaks. Don't want to go there. Thanks for the info. Did he mention how many threads to engage after finger tight by chance?

I've also considered junking the plugs I have and going with a tappered or NPT plug. Straight thread to NPT should seal though.

Comments?