Driving my 3.5 and very suddenly temp gauge went high, pulled over to check and the engine was very hot, blowing coolant and steam from pressure cap discharge. Trailered car back home, refilled with water, and what seems like is happening is that the engine itselt is getting very, very hot before radiator gets hot, like there is no flow. I flushed the radiator (flowed fine), pressure checked system at 15 psig, no leaks, also checked without thermostat installed, replaced thermostat, started back up, runs fine until gauge gets about 3/8 way up then suddenly overheats sevely, no bubbles in coolant and oil looks fine, so I'm hoping it's not a head gasket. Could this be the water pump ???? I guess if it seized up, it could just be slipping on the back side of the timing belt. Any help would be appreciated.

 

Fixed the problem, found two things, the timing belt wasn't even hardly touching the water pump pulley, the auto tensioner wasn't working, also the water pump was tight, all you could do to turn it with one hand. Replaced the water pump and the timing belt, soaked tension in Kroil, put back together, all happy and cool now !!!!!