What causes car temp to fluctuate?

Hey, my name is Dusty, and I'm one of the auto experts with RepairPal's Car Genius team. I'm here to help! If you've replaced the thermostat and water pump and properly bled the cooling system but observe the temperature gauge still fluctuating, consider investigating these potential areas: First, check the serpentine belt for proper tension (a slipping belt can affect water pump operation and other accessories), condition, and directional rotation; an improperly routed belt will cause the water pump to spin in the wrong direction, which can lead to temperature stability issues and overheating. Then, inspect the system for clogs, blockages, or air pockets that might hinder coolant flow. If you suspect air pockets are still present, re-bleed the system with the thermostat set to max-hot and allow it to run until the fans cycle at least 3-4 times while monitoring the coolant temperature. Then, allow the engine to cool and top off the coolant as needed. If these suggestions don't do the trick, you have other questions, or you'd rather take the car to a RepairPal Certified shop, feel free to contact us. 877-913-1554