[Michael C Henry]

A Stant pressure tester cheap, available everywhere.I got mine through Harbor Freight.Fill the system with coolant and start if presure climbs very fast you have a combustion leak.Did you get the thermostat in backwards? I'v seen bad thermostats also.Another one I've seen is that short little hose between the manifold and coolant pump.Had a bad place inside .It would blister inside (not visable from the outside )Would swell up and cut off flow thermostat bypass flow .Coolant temp would rise untill thermostat opened violently. temp was already out of site (460 truck)If the coolant is boiling it won't transfere heat.