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How to Bleed a Car Cooling System (Step-By-Step)

The cooling system in a car is responsible for keeping the engine at the right temperature, preventing it from overheating and causing damage.


The coolant, a mixture of water and antifreeze, is circulated through the system by the water pump, passing through the radiator, coolant hoses, thermostat, and coolant reservoir. If air gets trapped in the system, it can cause issues such as overheating and reduced performance.


In this article, we will go through the step-by-step process of how to bleed a car cooling system, including the necessary equipment, methods for different types of cars, and symptoms to look out for.

 

Table of Contents:


person adding coolant to a car

Parts of the Car Coolant System

Below are the parts and components used in a vehicles cooling system.


  • Radiator: The radiator is a component of the cooling system that reduces the coolant temperature as it passes through it. The coolant is cooled by the air passing through the fins of the radiator.

  • Coolant hoses: The coolant hoses are responsible for transporting the coolant from the engine to the radiator and back again.

  • Thermostat: The thermostat is responsible for regulating the flow of coolant through the system, ensuring that the engine doesn't overheat.

  • Coolant reservoir: The coolant reservoir is responsible for storing the coolant and providing a visual indication of the coolant level in the system. It also helps remove air from the coolant system and allows proper recirculation of the coolant.

  • Water pump: The water pump is responsible for circulating the coolant through the system.

  • Coolant: The coolant is a mixture of water and antifreeze that is used to keep the engine at the right temperature and prevent it from freezing in cold weather.


How Do I Get Air Out of My Cooling System?

The process of getting air out of the cooling system is known as bleeding the system. This process involves circulating the coolant through the system, allowing the air to escape and be replaced by coolant.


How Long Does It Take To Bleed Air Out of Cooling System?

The amount of time it takes to bleed the air out of the cooling system can vary depending on the method used and the condition of the system. In general, it should take around 20 minutes to bleed a vehicles cooling system.


What Equipment You Will Need to Bleed Coolant

When bleeding your car's cooling system, there are a few specific pieces of equipment that you will need to have on hand. These include the following.


  • Coolant: You will need a mixture of distilled water and antifreeze, also known as coolant, to refill the system after bleeding it. Be sure to use the correct type of coolant recommended by the manufacturer for your specific make and model of car. (Check coolant prices here)

  • Hydraulic floor jack: A hydraulic floor jack is necessary to safely lift the front of your vehicle so that you can access the bleed valve or the radiator cap. Make sure to use jack stands to support the vehicle securely when it is lifted. (Check floor jack prices here)

  • Jack stands: Jack stands ensure your vehicle is safely supported while its raised in the air, it is a must-have item if you are jacking up your car. (Check jack stand prices here)

  • Basic hand tools: You will need a few basic hand tools such as screwdrivers, wrenches, and a ratchet set to remove the radiator cap and to open the bleed valve if your car have one.

  • Clear plastic tube: A clear plastic tube is useful for attaching to the bleed valve and directing the coolant into a pan placed underneath the car.

  • Funnel: A funnel may be helpful for adding the coolant to the system without spilling.


Having all of these items on hand before starting the cooling system bleeding process will ensure that you have everything you need to complete the job efficiently and safely. Ensure the coolant mixture you have isn't expired and is within it's "use by" date.


Bleeding the Cooling System With a Bleed Screw

Bleeding a car's cooling system with a bleed screw is a straightforward process, but it's important to take the necessary safety precautions and follow the steps in the correct order. Below is a detailed guide on how to bleed the cooling system with a bleed screw.


  1. Safely jack up the front of the vehicle: Use a hydraulic floor jack and jack stands to lift the front of the vehicle to a safe and stable height. Make sure the vehicle is securely supported before proceeding.

  2. Remove the radiator cap: Locate the radiator cap and remove it. The radiator cap is usually located at the top of the radiator, but the location may vary depending on the make and model of your car.

  3. Attach a clear plastic tube to the bleed valve: Take a clear plastic tube and attach one end to the bleed valve and the other end into a pan underneath. This will allow you to see the coolant and any air bubbles that may be present.

  4. Turn the bleed valve 2 turns counterclockwise: Locate the bleed valve, which is usually located near the thermostat or the top of the engine block. It may be labeled or identified with a small arrow pointing towards it. Turn the bleed valve counterclockwise with a suitable spanner or socket.

  5. Fill the coolant system with distilled water and antifreeze (coolant): Use a funnel to add the coolant mixture to the system, filling it to the appropriate level.

  6. Switch on the engine (in neutral so the wheels aren't turning): Start the engine and ensure that the gearbox is in neutral so that the wheels aren't turning.

  7. Idle the car for 20 minutes: Allow the car to idle for 20 minutes to allow the coolant to circulate through the system and allow some of the trapped air to escape.

  8. Set the heaters in the car to maximum: Turn on the heaters in the car to maximum to help circulate the coolant through the heater core system.

  9. Rev the engine to about 3000 RPM: Rev the engine to about 3000 RPM to help circulate the coolant and remove any trapped air.

  10. Carefully open the air bleed valve: Slowly open the bleed valve to release any trapped air. You will notice the air bubbles coming out of the plastic tube.

  11. Close the bleed valve when the stream of coolant is free of air bubbles: As soon as you see a steady stream of coolant free of air bubbles flowing through the clear hose, close the bleed valve.

  12. Refill the coolant to the required level: Check the coolant level and refill it to the appropriate level if necessary.

  13. Test drive the vehicle: Take the car for a test drive and monitor the temperature gauge to ensure that the system is functioning properly. Be sure to check for any leaks and address them promptly.


It's important to note that the location of the bleed valve may vary depending on the make and model of your car, so it's a good idea to consult your vehicle's owner manual or a professional mechanic for the exact location of the valve.


How to Bleed a Cooling System That Doesn't Have a Bleed Valve

If your car's cooling system doesn't have a bleed valve, there is another method you can use to remove trapped air from the system. Below is a step-by-step guide on how to bleed a cooling system without a bleed valve.


  1. Safely jack up the front of the vehicle: Use a hydraulic floor jack and jack stands to lift the front of the vehicle to a safe and stable height. Make sure the vehicle is securely supported before proceeding.

  2. Remove the radiator cap: Locate the radiator cap and remove it. The radiator cap is usually located at the top of the radiator, but the location may vary depending on the make and model of your car.

  3. Fill the radiator with a 1:1 ratio mixture of distilled water and antifreeze: Use a funnel to add a mixture of distilled water and antifreeze to the radiator, filling it to the bottom of the