Chevrolet Repair: overheating, bleeder valve, waterpump

Question
not that i can tell
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-----Question-----
I have a 97 lumina and four months ago i replaced the thermostat and it was going through a gallon of coolant a month but i didn't see any leaks. It was running fine until yesterday and it started to overheat and the car died. it goes from cold to hot in a madder of a few minutes of driving. I turned the heater on and it is cold but it is stabilizing the temp and is running hot but not overheating yet. someone told me it might be my waterpump or thermostat. HELP
-----Answer-----
any oil in the coolant or coolant in the oil?

Answer
Well, because its getting hot in a matter of minutes, the first place I would start is the thermostat.
Then make sure the cooling fan is operational. Make sure it is full of coolant.
And check to make sure there isnt a bleeder valve to let the air out of the system which is usually done after repairs