Head Gasket Failure

TYPES OF HEAD GASKET FAILURE

External Coolant Leak - Coolant leaks out along the edges of the gasket from an internal coolant passage. This is often the result of loose or broken head bolts.

Combustion Chamber to Coolant Leak - Combustion pressure forces its way past the armored skirt on the head gasket and into a coolant passage.

Combustion Chamber to Combustion Chamber Leak - Combustion pressure forces its way past the armored skirt on the head gasket and into an adjacent cylinder.

Oil Passage Leak - Oil leaks out along the edge of head gasket from an oil passage.

SYMPTOMS

External Coolant Leak - Coolant is visible leaking between the head and block.

Combustion Chamber to Coolant Leak
- White smoke in exhaust. (1)
- Rapidly overheats.
- Emits coolant from spark plug holes during a compression check. (1)
- CO (carbon monoxide) detectable in radiator.
- Spark plugs fouled with coolant. (1)
- Oil contaminated with coolant. (1)

(1) Could also be caused by an intake gasket coolant leak.

Combustion Chamber to Combustion Chamber Leak
- Low compression in two adjacent cylinders.
- During a compression check, while one cylinder is on its compression stroke air is emitted from an adjacent cylinder and then drawn in during the intake stroke. This makes a very distinctive "whoosh-wheezing" sound.
- During a leak down check, air is emitted from an adjacent cylinder





HOW TO VERIFY THE PROBLEM
- Pressure check the cooling system and visibly inspect the block to head sealing surface for signs of coolant leakage.
- Remove all spark plugs and inspect for signs of coolant contamination.
- With all of the spark plugs removed, crank the engine with the starter for several revolutions. If a combustion chamber to coolant leak exists, coolant will be expelled from the associated cylinder.





WARNING: Keep clear of the engine compartment while performing this test. Coolant may be expelled from the spark plug holes with great force. Perform this test only with the engine cold.

- Perform a compression test of all cylinders while observing the radiator coolant level. Low compression on two adjacent cylinders or air bubbling out of the radiator during the compression check may indicate a head gasket problem.
- Inspect the oil for signs of coolant contamination.
- With light contamination, the oil will a light creamy coffee color.
- With heavy contamination the oil may appear thick and light tan in color.
- If the engine has sat for a while, the water and oil may have separated. While draining the oil, the coolant will drain out first, followed by the oil.

NOTE: Oil contaminated by coolant may also be caused by an intake manifold leak.



- Perform chemical combustion leak check. Any evidence of combustion gasses in the coolant indicates a head gasket leak.
- Perform cylinder leakage check.
- Watch for bubbles in radiator (combustion chamber to coolant leak).
- Listen for air in adjacent cylinder (combustion leak between cylinders).

NOTE: A cylinder leakage check utilizes regulated low pressure air to pressurize individual cylinders.