How to Flush a Radiator

by Contributor

Flushing the radiator of your car can help prevent blockages or leaks that can cause extensive damage to the cooling system. Failing to inspect and flush your radiator on a regular basis (at least every six months) could lead to a roadside breakdown, possibly in the middle of nowhere.

Turn the engine off and allow it to cool to non-operating temperatures. Cover the engine compartment, with the exception of the radiator, with an approved tarp or blanket in order to eliminate splashes on the rest of the engine block.

Remove the radiator cap. Remember to do this only after the engine has cooled completely.

Check the radiator hoses for damage. Feel the hoses for signs of brittleness or excessive moisture.

Drain the liquid inside the radiator into a plastic tray or tub. If the liquid is fairly clean, proceed with the flush. If it is unusually dirty, check the exterior of the radiator for excessive rust or damage.

Flush the radiator with cold water from a garden hose. Let the water overflow the top of the radiator until it comes out clean.

Perform a reverse flush by replacing the radiator cap on the top, and removing the cap on the bottom of the radiator. Again, let the hose run until the water comes out clean.

Attach the garden hose to the engine cooling jacket and flush it out in the same manner.

Replace all hoses and the bottom radiator cap once the water has completely drained.

Add coolant to your radiator to the level recommended by the manufacturer of the vehicle.

Inspect the radiator cap for excessive rust. If it looks fine, screw it back on the top of the radiator.

Remove the engine cover, start your engine and watch for leaks. If you do not see drops of coolant developing on the ground beneath the car, take it for a spin around the block to ensure you have flushed your radiator correctly.


  • check If your vehicle has a factory sealed radiator, you will not be able to flush it yourself on a regular basis. Instead, have the dealer check it as part of your normal maintenance routine, and periodically check the exterior of the radiator yourself for leaks or excessive rust.


  • close You should have your radiator replaced completely if it continues to leak after a flush. Don't rely on leak sealer, which is a temporary solution at best.

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