Hi i have a 92 APV lumina 3.1 throttle body injected with 128,000 miles
Lets see i had my son fill the coolant reserve and I never checked hw overfilled it today when I parked all i heard was a loud noise sounding like a boil and there was coolant leaking I did take off the lid and after a few mins it did receed and stop. Could this be due to the fact that he overfilled or is it a
bad rad?
bad pump?
bad thermostat?
I need this car other one died and this is the only one I have? I have had no prblems until he over filled the reserve.
Michele

Do not loose money on any of the items mentioned before checking for these other symptoms:
- poor/sporadic heat from heater
- erratic temperature needle
- overheating
- steaming
It is just too common for 3.1 to have head gasket failures and a lot of people spend tons of money on radiator, colant pump, thermostat, just to end up with the unwanted conclusion.
THis is not funny, but you must consider the possibility of such occurrence.