I have the 4.3l in my toyota and its not flowing water to the radiator all the time. Symptoms are surges every few seconds when its hot not a constant flow. I can watch the hoses on the outlet shrink and expand when it surges. The highest hose has a vent, I can open to let air out. The radiator is about 2'' higher than the outlet hose.
Do you guys put a higher gpm pump on when using a rear radiator? Or am I missing something?