How to know if your head gasket is bad

Written by r.l. cultrona
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The head gasket is sits between the engine block and the cylinder head. This gasket seals the engine cylinders to keep coolant from leaking into the engine and to ensure maximum compression of its combustion chamber. This gasket is the most important seal in an engine and can cause major problems if it goes bad.

Skill level:
Moderately Easy

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Things you need

  • Mirror to inspect the gasket
  • Flashlight

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  1. 1

    Pull out the dipstick and check the oil for the presence of coolant. If the head gasket breaks, it will usually cause coolant to enter the oil line. Coolant will look milky in the oil. If you are still unsure, drain a little oil into a pan and check it under a light for spots.

  2. 2

    Turn the car on and leave it in park. Step behind the vehicle to inspect the exhaust pipe. If there is a problem with the head gasket, the exhaust will be white. There may also be a sweet smell emanating from the exhaust pipe

  3. 3

    Open the bonnet and shine the flashlight to the area where the engine block meets the compression cylinder. Use a mirror to inspect hard to see areas. You are looking for any obvious cracks or coolant leaks, which can indicate a broken head gasket.

  4. 4

    Place the car in park and slowly rev the engine. If the car feels like it is about to stall while going back to the idle position, this could also be a sign of a bad head gasket. The reason for this is when a head gasket is bad, there may not be enough compression to keep the engine going. It may not completely stall, so try this a few times to get an indication of what is going on.

Tips and warnings

  • Try performing these tests on a warmer day as the car will perform better, allowing you to get a better diagnosis.
  • If you think your head gasket is about to go, get to a repair shop immediately. A blown head gasket can cause a sudden loss of engine power, which can leave you stranded on the highway.

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