Problem with overheating. Changed thermostate, cap. Radiator not leaking. Can drive car most of time, but then after using it for a long period of time (say 150 miles or more) it runs hot. Dont think it would be water pump, cause that was cause overheating earlier. Belt seems to be running. Any ideas....

 

Did you bleed the cooling system as you filled it back up? Air in the cooling system is a cause of overheated.

 

Yes, check the level in the radiator, not the plastic tank before starting when the engine is cold. It should stay full to the top. Water pumps don't usually fail in a way that they turn but don't pump, unless there is severe corrosion caused by using plain water or very old coolant mixture in the system. Blockage of the radiator or airflow problems (clogged or missing fins) would lead to overheating primarily in highway driving.