Typical leaks between cylinder head, cylinder-head gasket, and engine block involve gas, oil, or coolant leakages. These leakages occur between combustion chambers, into the coolant circuit, or to the environment. Gas leaks can result in fatal engine damage within a very short time and oil leaks can cause severe environmental pollution.

Pressed-in dirt or foreign objects as well as rough surfaces also cause damage to cylinder-head gaskets. Component unevenness leads to gas blowby between the combustion chambers, and consequently to gasket failure.

Therefore, thorough cleaning of the sealing surfaces is essential before installing the cylinder-head gasket.

Damage Analysis of MLS Cylinder-head Gaskets
Damage to multi-layer steel cylinder-head gaskets mostly involves two sealing elements: beads and elastomer coatings.

Bead Fractures due to excessively high Component Dynamics
Possible causes for excessively high component dynamics are faulty, reused, or unlubricated cylinder-head bolts; incorrect bolt torquing due to excessively high friction during installation; and damage to cylinder head or engine block. Component distortions can also be the result of engine overheating. Similarly, if an engine is operated under pinging conditions (pre-ignition), the high temperatures and pressures can lead to higher component dynamics and possible bead fractures.

Detached Elastomer Coating due to Overheating
Classical causes for overheating are defects of the water pump, radiator, thermostat or hoses, but also insufficient coolant or incorrect venting of the coolant system can lead to thermal problems. Failure of the catalytic converter can also result in higher temperatures due to increased exhaust back pressure.

Elastomer Coating destroyed by Antifreeze Agents
Contact with antifreeze agents that have not been approved can cause the elastomer coating to become detached from the metal surface. Subsequently, the dislodged elastomer particles can clog the coolant channels and interrupt the coolant flow. The result is an overheated engine. Other typical damage profiles for MLS cylinder-head gaskets are destroyed combustion chamber seals due to incorrect cylinder liner protrusion or faulty liner flange seats, as well as severely damaged Ricardo squish areas due to detached swirl chambers.

TIP FROM THE EXPERTSP
Cylinder-head bolts tightened using the torque-angle method are elongated permanently. After disassembly, they are clearly longer than new bolts. If reused, they can break. Therefore, new cylinderhead bolts should always be used when replacing a cylinder-head gasket.