How to Bleed Air from the Radiator?
3 Answers
Methods for bleeding air from the radiator: Drain half of the coolant from the radiator, start the engine and keep it idling, then slowly add coolant until the radiator is completely filled. The presence of air in the radiator essentially means there is airlock in the antifreeze, which can hinder the smooth flow of the coolant. The car radiator, generally referring to the heat exchanger, is part of the vehicle's cooling system. In an engine's water-cooling system, the radiator consists of three parts: the inlet chamber, outlet chamber, main plate, and the radiator core. Car radiators are primarily made of two materials: aluminum and copper. The former is used in general passenger vehicles, while the latter is employed in large commercial vehicles.
After working in the auto repair shop for so many years, air entering the radiator is a common issue that can easily lead to engine overheating or even complete failure. The key to bleeding the air is to get the system running to expel the bubbles. The steps are actually quite simple: First, make sure the car is parked on level ground. When the engine is cold, open the hood and locate the air bleed screw or valve near the radiator or engine (usually at the highest point of the cooling system). Use a wrench to slightly loosen it, but do not open it completely. Then, start the engine and let it run until it reaches normal operating temperature. Once the cooling fan starts running, fluid carrying bubbles will flow out from the bleed hole. When the fluid coming out is uniform in color and free of bubbles, tighten the bleed valve securely. Don’t forget to check the coolant level during the process. If it’s low, promptly add the manufacturer-recommended coolant until the radiator is full. Be cautious of hot fluid to avoid burns—wear gloves for protection. Finally, turn off the engine and check all caps to ensure they are sealed properly; otherwise, air may re-enter.
As a car owner who has personally experienced radiator air issues, I panicked when the coolant temperature warning light suddenly came on. While bleeding the air myself, I learned a practical method: Park the car on level ground and slightly elevate the front wheels with bricks to help air bubbles gather. After starting the engine, turn on the AC heater to activate the system circulation, making it easier to purge air. Locate the small air bleed valves on the radiator (positions vary by model—check the manual), gently loosen one, and you'll see bubbles gurgling out. Be patient and wait a few minutes until the fluid flows steadily without bubbles before tightening it. Monitor the coolant level during the process to ensure it doesn't get too low, and keep spare coolant handy. If unsure about the bleed valve location, searching for model-specific video tutorials online is a huge help. After completing the process, take a short test drive to confirm normal coolant temperature.
