Pushing out water
 

I have 1990 Supra Turbo that is pushing water out the overflow tank. It is not over heating. It has a 13 pound pressure cap on the radiator. Forty thousand miles ago it had the head gasket replaced. Which did its job until now when the above started. I had it checked and the mechanic said it was the radiator cap which I had just replaced that and the radiator but he replaced the cap and charged me $125.00 for the cap and test and it still pushes water out. My question is should I try another radiator cap and should I put a higher pressure one on and if so how high of one should I go? If it is not over heating does that mean it is not a head gasket that is the problem? The reason I replaced the radiator was just to rule it out. I can definitely see the water coming out the hose of the overflow tank. I fill the radiator to the top and I fill the overflow tank to the maximum line and than I go for a ride and the over flow tank fills to the top and the water starts to come out its hose. The temperature gauge in the car stays between cold and hot if I had to guess I would say about 150 degree. What are your thoughts and suggestions? There is no water in the oil!

After you take it out and it fills the overflow tank, 1) does it draw any back into the radiator as it cools, and 2) what is the water level in the radiator (after it cools back down)?

I am not sure I will have to check and get back with an answer. Thanks.

It appears that some of the water goes back into the radiator but the radiator ends up about 1/2 to 3/4 of an inch below full.
The overflow tank is about two inches low of water at that point. As a point of information I had to replace the head gasket about thirty-five thousand miles ago.

Are you running a properly mixed coolant (50/50 antifreeze to water or similar?) Less antifreeze and more water will mean a mixture that boils at a lower temperature, which can cause increased cooling system pressure that can cause the cap to open lower than you would normally expect it to.

Your coolant temp reading bothers me. Unless someone put a VERY cold thermostat in the car, it should be reading higher than that at operating temp. My car has a 180 thermostat, and at operating temp it is just a little under the halfway mark on the gauge. The water temp sending unit for the gauge is usually after the thermostat, so it will read warm water once the thermostat opens. I think if I were in your situation, I would test (or rather replace) the thermostat, and check for proper operation of your water pump (assuming you have a good mix of antifreeze/water).