Overheats in still traffic or idle, cannot find a coolant leak thermostat is good bc both hoses feel same temp and car reaches operating temp good. Replaced the aux water pump thats electric and helps send coolant to rear heater core bc it was leaking. Have to keep adding coolant, oil doesnt look mixed with coolant or vice versa. Fan clutch feels viscous still.
My car has 173 miles.
My car has an automatic transmission.
It seems like you have an air flow issue or air in the system. The fan clutch should spin with a small amount of resistance when the engine is cold. With the engine up to temperature, the fan clutch should be much tighter and the fan should be hard to spin by hand. If you do not notice a significant change of resistance, I would suspect the fan clutch to be bad.
Also, check to make sure that you have bled all of the air out of the system. Sometimes air will cause the water pump to work inefficiently at idle, but once you are moving, the increased flow overcomes the inefficiency of the pump. A pressurized leak check can be used to determine if you have a leak, and helps locate the leak by forcing it to leak under pressure. If you need help testing your system, a certified technician, like one from YourMechanic, will be able to test your cooling system to determine cause of the overheating issue.
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