I have been slowly losing coolant, yet no puddles are ever evident. I have replaced radiator, thermostat, top & bottom radiator hoses. After a few hundered miles of driving with a full radiator (burped & inspected 3X), the 4runner (1993 3.0, 4x4) will start running hot. Sometimes the needle on the gauge will start dancing from normal to far left and anywhere in between. Sometimes it just sticks to the futherst left of the gauge like it went to sleep!! Sometimes it starts creeping to the ever ominous "redzone".
I can acknowledge that I may need an new sending unit, but after letting the motor cool to cold, the radiator sucks down up to a gallon of mix depending on how much I have driven it. I have about ruled out the infamous HG (the motor has around 50K on it)...
What other components of the cooling system could be the cause??