How to Check for a Blown Head Gasket on a Car

Written by adelaide damoah
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How to Check for a Blown Head Gasket on a Car
(knuckle image by Witold Krasowski from

The head gasket prevents leakage of vaporised gas, engine oil and coolant. A blown head gasket leads to chronic engine overheating, oil dilution and a reduction in engine power. Checking for a blown head gasket can reduce the chances of permanent damage to your engine. How often head gaskets fail varies between car models. In general, to prevent a head gasket in good condition from blowing, re-torque the engine, drain and refill the cooling system and check the head gasket annually.

Skill level:


  1. 1

    Check the oil dipstick for the presence of brown foam. This indicates water in the oil reservoir caused by combustion gases leaking into the cooling system and is symptomatic of a blown head gasket.

  2. 2

    Note any frequent stalling of your vehicle or if it makes chugging sounds while you are driving. These are indications of a blown head gasket.

  3. 3

    Check the temperature gauge while you are driving. If the engine is overheating, the gauge will be in the red, and steam will be coming from under the hood of the car. If the engine is overheating, stop the car immediately, turn off the engine and open the bonnet to allow the hot gases to escape. Wait for the engine to cool down completely before adding water to the water reservoir and changing the coolant. Have the car towed to your nearest mechanic.

  4. 4

    Look for white steam coming out of the exhaust as you drive. You should be able to see this in your rear view mirror. Notice if there is a sweet smell coming from the exhaust pipe as this is a sign that the antifreeze has leaked into the combustion chamber. These are both signs that you may have a blown head gasket.

  5. 5

    Check the radiator and look for oil in the coolant. Note any foaming, gargling or bubbling from the radiator. If your car uses more radiator fluid than usual, this can be a sign of a blown head gasket. Check the radiator for signs of coolant where it should not be present, such as on the spark plugs. This may happen because of pressure building up in the cooling system, causing the coolant to rapidly bubble up and overflow.

  6. 6

    Take the car to a mechanic who will perform a compression test with a compression gauge. The mechanic may follow up this test with a pressure test and a cylinder leak-down test which can confirm a blown head gasket.

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