How to Replace a Radiator Drain Plug O-Ring

A car radiator leaks because either the radiator hose is punctured or the radiator drain plug O-ring is damaged. Your car's radiator may be leaking and you are at a loss of what to do.

A car’s drain plug is normally at the bottom of a radiator. The plug is used to drain used radiator fluid. The radiator fluid should be replaced regularly after flushing the radiator so as to amplify your car’s performance.

Eighty percent of radiator leaks due to damaged radiator drain plug O-rings. This means that whenever you have a radiator leak, the radiator drain plug O-ring is the first thing you can check. If you suspect or find that it is indeed damaged, the following steps will help you replace it yourself.


A new plug O-ring for the radiator

A dry towel

Vaseline or any other ideal silicon lubricant

A bucket or any other plastic container

A screwdriver or a wrench

Heavy work gloves

Step 1: Turn the Engine Off and Remove the Car’s Radiator Cap

You should turn off the engine of your car and wait until the engine cools down completely before you can work on its cooling system. This may take quite some time if especially it has been in use. Put on some work gloves. Then place the dry towel on top of the car’s radiator cap and loosen it counterclockwise. The cap will come loose once the catch disengages. Keep your face at a distance, since once the cap is disengaged, pressure will escape from the car’s radiator. Remove the cap slowly so that the pressure is released gradually until it has escaped fully. Once the pressure is gone, remove the cap completely.

    Step 2: Drain the Radiator and Remove the Damaged O-ring

    Place the bucket underneath the radiator’s drain plug. Using your screwdriver, turn the drain plug in the counterclockwise direction until it comes loose. Let the radiator fluid empty into the bucket. Next, apply some silicon lubricant or Vaseline on the O-ring and attempt to slide it off. It should easily come off from the drain plug.

      Step 3: Insert Your New O-ring and Replace the Plug

      Before you insert the new O-ring, apply some silicon lubricant or Vaseline to it. Then fit it on the drain plug and ensure it is completely within the provided groove. Place the drain plug back into the radiator. Slowly turn it in a clockwise direction until it is tightened. Don’t over tighten it.

        Step 4: Refill Your Radiator with Antifreeze

        Now you can add a new mixture of water and half antifreeze into the radiator. Each of these liquids should be mixed to a ratio of 1:1. Ensure that the radiator is completely full with the mixture. If there is a reservoir tank, fill it with the mixture too.

        Without capping the radiator start the engine and run it for some time, so that the radiator distributes the radiator fluid to the entire cooling system.

          Step 5: Refill the Radiator Fluid and Recap the Radiator

          There will be more space now for the mixture of water and antifreeze coolant. Refill the radiator and the reservoir tank. Insert the radiator cap back, and turn it in a clockwise direction until it is securely tightened.

            Even before leaks begin, it is important that you replace the radiator drain plug O-ring every time you refill the radiator fluid or flush the radiator. With a damaged O-ring, the car’s water and antifreeze coolant can be lost and cause your car to overheat easily and frequently.