They seal off an intake or exhaust port with a piece of rubber that has an air hose and gauge attached. They said it should read around 18 psi, but mine were reading from 11 to 15 psi.
That test checks for valve seat sealing, NOT cracks into the cooling system. Find a machine shop that can do a pressure test of the cooling passages, and/or a magnaflux test where the head is magnetized and an indicator powder is sprayed over the surface to find hairline cracks. So far, nothing definite has been done to detect any cooling system/compression leakage. If you put it back together now, chances are the problem will still be there.
Jerry
