My LS1 just started running hot. I actually noticed because I parked it at a friends house and the fan ran for a while after the ignition was off. The coolant level is fine. I haven't checked the temp sending unit yet but was wondering if anyone has had this or a similair expereince and possibly what the problem was with their car.

 

I'd start with the easy stuff - make sure the radiator is clear, radiator cap is holding pressure, thermostat not sticking, radiator fluid level when cold...was it puking/bubbling fluid?

 

Thanks for responding. The radiator was not bubbling fluid. It is not obstructed. Fluid level was fine. I do not think the thermostat is sticking because if it was stuck open it probably would not reach the temperatures that it is as fast as it is and if it was stuck closed the fluid in the radiator and reservoir would not be getting so hot. I assume the radiator cap is holding pressure as without the pressure the water would boil and I would lose fluid.

 

Both of these assumptions are wrong. The cooling system still bypasses coolant to the radiator even when the thermostat is closed. Just not as much.
And the water that would go out past the radiator cap goes into the coolant resevoir under the battery. That is part of the normal function of the system.

 

Not sure about the first part but the second part is partially correct. If the cap does not hold pressure then the reservoir will not be able to hold the fluid and you would lose fluid. This began today by the way. I went ahead and replaced the radiator cap but its still running hot.