How to Remove an Airlock From an Auto Cooling System

Written by thomas west
  • Share
  • Tweet
  • Share
  • Email

An automotive cooling system is a closed, pressurised system containing coolant -- usually a mixture of antifreeze and water. During some cooling system maintenance procedures, such as water pump or thermostat replacement, air may enter the cooing system. Air in the cooling system may create an airlock which keeps the cooling system from being filled to its full capacity of coolant. An airlock in the cooling system may cause the engine to overheat and needs to be purged.

Skill level:
Moderately Easy

Other People Are Reading

Things you need

  • Hex wrench or box-end wrench set (if the cooling system is equipped with bleeder screw)
  • Coolant

Show MoreHide

Instructions

    Bleeder Screw Equipped

  1. 1

    Open the bonnet and allow the engine to cool for at least one hour if the vehicle has been driven recently.

  2. 2

    Locate the cooling system thermostat housing by tracing the upper radiator hose to its attachment point at the engine. Note that the end of the hose is attached to the thermostat housing which is bolted to the engine block.

  3. 3

    Locate the bleeder screw mounted into or near the thermostat housing. Proceed to the next section if there is no bleeder screw.

  4. 4

    Start the engine. Depending on the vehicle, loosen the bleeder screw with a hex wrench or box-end wrench slightly in a counterclockwise direction.

  5. 5

    Allow the engine to run until a stream of coolant flows from the bleeder screw with no air bubbles. Close and tighten the bleeder screw. Shut the engine off. Top off the coolant either from the radiator or coolant recovery tank, depending on the fill location of the vehicle, with coolant once the engine has cooled. Close the bonnet.

    Without Bleeder Screw

  1. 1

    Open the bonnet and allow the engine to cool for at least one hour if the vehicle has been driven recently.

  2. 2

    Remove the radiator or coolant recover tank cap, depending on the vehicle, and place it aside. Top off the coolant so that the level is at the full mark on the recovery tank or to the bottom of the filler neck on the radiator, if necessary.

  3. 3

    Start the engine and allow it to reach operating temperature, which is usually about 15 to 20 minutes. Turn the heater and defroster to its maximum temperature setting so that coolant in the heater hoses can be purged also. Be aware of coolant bubbling from the radiator or coolant tank opening as air is expelled.

  4. 4

    Shut the engine off and allow it to cool. Observe the level of coolant in the radiator or coolant tank. Add coolant to bring the level back up to normal as air bubbles are expelled.

  5. 5

    Repeat the process to ensure all air has been expelled. Let the engine cool over overnight and check the coolant level in the morning, if possible. Replace the radiator or recovery tank cap and close the bonnet. Check the coolant level every day for a few days and top off as needed.

Tips and warnings

  • Keep an eye on the temperature gauge or light during this procedure. Shut the engine off if it begins to overheat.

Don't Miss

Filter:
  • All types
  • Articles
  • Slideshows
  • Videos
Sort:
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the eHow.co.uk site, you consent to the use of cookies. For more information, please see our Cookie policy.