The problem could be caused by a number of small factors.
I've drained the radiator (not block) several times through the course of its life and didn't see any evidence of sediment, so I didn't expect rust or scale in the engine. I was probably wrong. The radiator was serviced a few years ago and the guy didn't think that there was a flow problem. He didn't do a flow test, however. The bottom tank always seems very hot like it isn't cooling.
I am using the chevy water outlet neck with the small hose and small water neck on the radiator. The gmc used a larger diameter hose but is it really necessary? I do have a heater but it has a valve which can completely shut off the water so I guess that a bypass may still be necessary?
I have a line from the back of the head through the manifold (heated) and up to the lower part of the thermostat housing. I am using a 7lb cap but without an overflow tank so the radiator has some air in it all the time.
I tried a high flow thermostat and it ran hotter on the hiway and then wouldn't warm up around town. I know this contradicts all the screaming that I did earlier about needing high coolant flow :rolleyes: . I did a lot of reading on the topic and think that there is more to it than I realized. Sorry if I offended anyone.
I guess I know where to begin,
thanks for the suggestions.
jason
