Well, I took out my CTS to replace the thermostat housing and I put it back in the new one and it leaks. I didn't but any kind of sealant or anything in the threads because I didn't know what to use. Should I put some sort of sealant or something in the threads or what else should I do?

 

use some teflon tape, and dont overtighten it.
NPT threads have a "leakage path" that needs to be filled with sealant.
(marked with red)


Wrap it in 3 wraps of teflon tape in the opposite direction of threads. Tighten to finger tight, and then 3 complete turns with a wrench.
If it still leaks after that, you pry need a new thermostat housing, the threads are screwed.

 

What kind of sealant do you recommend?

 

Teflon tape, like I mentioned.

 

Ohh. When you said "filled with sealant" I thought of a paste or something on top of the Teflon tape; my bad. Thank you! I will go do this right meow and see if my problem is solved.

 

http://www.mechanicsupport.com/articleFittingTight.html