you need a leak rad tester it pops on where the cap gos and then you pump up the system dont go over 20 psi you can moniter the psi if it drops you got a leak plus if it an external leak you can see it if its an internal leak watch the top of the pistons threw the plug hole.this will help you see if you need a head gasket.head gaskets are a little hard to change you have to re time the cam and get all the rite tork speks(i posted them a day or two a go for the b16 and h22 the header was tork spek help 10-11) also when you take it apart make shur its on tds this will make it easyer to put back to geater.is also a good idea to take the head to a machine shop and have it checked for worp if it badly worped and you just do a new gasket it will still leak. hope this will help a little