It started with the temp. gauge freaking out all the time. Then finally it overheated. So we bypassed the heater core cause it was leaking. Then flushed the system and changed thermostat. Two weeks later overheats. Now it just goes from zero to red line, it does not bob around. So I check the system, here is the weird part, the engine is overheated yet the water pump hose is warm, the radiator is cold, and the overflow does nothing. Oh yeah and the top house to the thermostat is flamming hot.
After having it checked they say replace manifold gasket. I do this (by the way when it says 14ft lbs on upper intake listen. I broke the first intake.). It still does the same thing. So I do another thermostat, same thing. This time I checked T. stat in boiling water and it works. Now I replace the water pump just becasue it was cheap enough, and then I preasurised the coolant system. Same dang thing.
I dont think bypassing heater core has anything to do with it, but I could be wrong.
All I know is there are no signs of bad head gasket. The engine temp goes to red after a few miles, and yet all is cool except the upper radiator hose.

Please help me figure this out, please!
I do know that the whole coolant system should be hot when the engine overheats, and even with a bad head gasket the coolant would still circulate.