Q: My car is running hot. Do I need a thermostat? 2005 Nissan Maxima

Hi There, It sounds like you do have a faulty thermostat. The thermostat regulates the flow of the coolant in your car’s engine and controls when the coolant flows in and out of the motor from the radiator by opening and closing at specific temperatures. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. When the thermostat is stuck open it can cause the coolant to circulate constantly resulting in the motor never reaching the correct operating temperature.

Hi there - if the thermostat is stuck closed, then yes, that is the source of your overheating problem. However, it sounds like you have good coolant flow to the radiator. If so, the radiator may be clogged, and need professional cleaning or replacement, or the auxilliary fan may not be coming on when needed to cool things down. If it doesn’t come on at all (or only when you turn on the air conditioning), the coolant temperature switch on the radiator may have failed. Lack of aux fan function will allow the engine to overheat in traffic for sure. I recommend an overheating inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.