Common Symptoms of a Faulty Cylinder Head Gasket(s)

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The Cylinder Head Gasket is located between the mating surfaces of the cylinder head and the engine block. Its primary function is to separate the combustion chamber from the oil and coolant passages in the engine block.

When a cylinder head gasket begins to fail or deteriorate between a combustion chamber and a coolant passage, combustion gases can escape the combustion chamber and enter the cooling system. When a cylinder head gasket begins to fail or deteriorate between a combustion chamber and oil passages, oil can enter the combustion chamber and be burned in the combustion process.

What Causes a Cylinder Head Gasket to Fail?

Incorrect Ignition Timing: When fuel ignites at the wrong time, either premature or late during an engine's cycle, such as in pre-ignition or detonation, an intense build-up of pressure in the cylinder can occur. This sudden increase in pressure can strain the head gasket to the point of failure.

Overheating: Overheating can be detrimental to the engine's metal components and mating surfaces, causing thermal expansion and warpage. This includes the cylinder head gasket, the engine block and the cylinder head. Warping may result in an uneven mating surface between the engine block and cylinder head. A quickly overheating engine may be traced back to air in the cooling system.

Incorrect installation: If the head gasket was installed improperly, or without correctly diagnosing the root-cause of previous gasket failure, it's unlikely to maintain a proper seal. If you recently replaced a head gasket but encountered problems shortly afterward, it's possible that there was an issue with the installation.

Wear and Tear: Normal wear and tear, including heating and cooling cycles will eventually cause a head gasket to deteriorate. It is important to note that head gaskets do not usually fail unless something causes them to fail.

Common Symptoms of a Faulty Cylinder Head Gasket

Overheating engine

When an engine overheats due to a failed water pump, low coolant, extreme temperatures, a failed radiator fan or coolant hose, higher engine temperatures are the result. These temperatures can warp the metal mating surfaces and cause a cylinder head gasket to fail. After an engine overheats, you may notice increasing temperatures, an illuminated Malfunction Indicator Light (MIL) for reduced engine performance, or white smoke coming from the engine compartment. This condition can also be accompanied by a sweet-smelling odor from the engine compartment or exhaust system.

Decreased Engine Performance, White Smoke, and Coolant Consumption

If the head gasket fails between the combustion chamber and coolant passages, white smoke may appear at start-up or while driving, although this symptom may not always be present. Compressed air can leave the combustion chamber and enter the cooling system while operating normally, pressurizing the cooling system and causing hoses to fail, a water pump to leak, or a radiator neck or cap to fail. This can further present itself in the form of coolant consumption.

Prolonged driving can eventually lead to starting or cranking issues. As the combustion chamber wears away at a head gasket, more compression is lost to the cooling system and the engine may be difficult to start. This is a low compression situation where a combustion chamber cannot produce enough compression to properly turn the engine over. Additionally, driving with a failed head gasket will eventually introduce coolant into the combustion chamber, causing misfires, more white smoke, and faster coolant consumption.

Oil Consumption, Blue-Gray Smoke and a Milky-White Oil Filler Cap

When a head gasket failure occurs between a combustion chamber and an oil passage, oil can be consumed in the combustion chamber. The oil becomes part of the combustion process and presents as blue-gray smoke from the exhaust system coupled with increased oil consumption. A head gasket can also fail at both an oil passage and a coolant passage. When this occurs, the underside of the oil filler cap can get a film of a milky-white residue that is a combination of coolant and oil. This can be verified by checking the engine oil for change in color or texture, or by a sweet smelling odor in the oil.

External Leaks

A head gasket failure can cause similar issues both internally and externally. When the gasket fails, it allows oil or coolant to leak not only into the engine or cooling system, but also outside the engine, resulting in visible leaks at hoses, seals, or water pumps. When combustion chambers leak into the coolant system, the cooling systems are pressurized beyond their designed operating pressures, and components such as hoses and seals in the cooling system can fail, repeatedly.

Identify A Faulty Cylinder Head Gasket with the Innova Scan Tool

The Innova Scan Tool is ideal for both static and on the go applications. It quickly retrieves Diagnostic Trouble Codes, available Freeze Frame Data, OBD2 and OEM Enhanced Live Data Stream information and Code Definitions as well as DTC Severity and I/M Monitor Status, (Smog Check Readiness).

Please visit us at innova.com/support or pro.repairsolutions.com/Support for additional information.

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