1999 Subaru Outback 4 cyl All Wheel Drive Automatic 100000 miles
my car just started to overheat the other day. It would rise in temp slowly and then quickly go back to normal, So I replaced the thermastat. The car still would overheat after replacing the thermastat. I took the thermastat out and drove the car for an hour without it even coming normal operating temp. So I put another thermastat in and it is overheating again. Today the heater would come and go even with the temp above normal and it is full of antifreeze. The temp did not get high enough or for long enough to do damage. Can the water pump quit pumping. It seems to be a circulation problem. No bubbles in the radiator and no water out the exhaust.
When the car gets about middle temperature feel the upper and lower radiator hose, if the bottom one is significantly lower then you should check the water pump, sometimes the fins in there become corroded and sometimes disentinegrate. If the water pump is good then flush the system.
If the hoses are both the same temperature then make sure the coolant fan is coming on.