The poppet valve actually opens and freeflows water thru the engine in a sense bypassing the thermostats, correct? At what pressure should it open and how much should the pressure drop? My overheat buzzer has gone off at cruising speed, around 4K rpms, twice. Hasn't at idle or at WOT and when it does I'm showing around 8psi water pressure. Gonna have a look at the waterpump tomorrow , maybe 10 hours on it, and do some backflushing of the block while I have the lower unit off. Not sure whats going on