Q: What makes a car's temperature normal at idle but hot while driving? - 2000 Chevrolet Malibu

This may be related to a few different things, such as a clogged radiator not allowing coolant to circulate properly, a thermostat that may be stuck closed not allowing coolant to flow through the motor, or potentially a bad coolant fan switch that may be operating erratically or intermittently.

When a thermostat is stuck closed, this does not allow coolant to pass through the engine when the coolant reaches the specified temperature. Coolant fan switches are also designed to trigger the cooling fans to come on the same way when the coolant reaches a specific temperature. When this switch is faulty, this may cause them to come on sometimes not at all or intermittently.

You may want to consider having a professional mechanic, such as one from YourMechanic, come to your location to perform an inspection into why the car is running hot and suggest any necessary repairs.