Q: My 1998 Buick Park Avenue only runs hot when in traffic or just idling. What's the cause of it running hot?

Either the cooling fans on the radiator are not working properly or the radiator is plugged up to where there is a restriction when the engine’s water pump is running at a slow speed. If you suspect that the radiator is plugged up, try running the engine at a higher rpm when stopped and the transmission in neutral. If the coolant temperature gauge drops, then the radiator needs flushed or replaced. If the engine tends to not cool down but rather overheat, then the cooling fans are not working.

Then you would need to check the cooling fan relay and see if its clicking on. If the relay is not clicking on but there is power to the relay, then the cooling fan relay needs replaced.

If the cooling fan relay is not clicking on and there is no power to the relay, then there is a break in the wiring from the fuse box to the relay or the cooling temperature switch has failed.

If the relay is working and clicking but there is no power to the cooling fans, then there is a break in the wiring from the relay to the butt connector. If there is power to the motors but the fans are not coming on, then the cooling fan motors need replaced.

If you need further assistance with your engine overheating at a stop, then seek out a professional, such as one from Your Mechanic, to help you.