The cylinder head is an essential component of all combustion engines, the failure of which can cause catastrophic results.
Essentially the cylinder head and head gasket seals the top of the cylinders creating the combustion chamber. It also creates a solid and sound environment for the valves, spark plugs and fuel injectors to feed the chamber with air and fuel. Cylinder head repairs are the most common task undertaken by an engine repair shop.
Cylinder heads are precision milled to very fine tolerances specified by the manufacturer and require specialist equipment and highly skilled technicians.
The most common cylinder head repairs are:
· Cracked cylinder head: Hairline cracks can form in cylinder heads, usually caused by overheating or rapid temperature change. It can also be caused by the different expansion and contraction rates if an aluminum cylinder head is mounted on a cast iron engine block. Many drivers mistakenly pour cool water into the radiator when their vehicles overheat, in an attempt to bring the temperature down. This is also can cause a cylinder head crack, because the rapid temperature change can cause cracks due to thermal stress. Cracked cylinder heads can be repaired by welding the offending crack then milling the repair back to factory specification.
· Warped cylinder head: As with cracking, cylinder head warping is usually caused by overheating or extreme temperature fluctuations. Repairs should be made by regrinding the cylinder head back to a true state before the head cracks.
· Corroded cylinder heads: Corrosion is more common in old cylinder heads where porous spots are formed, usually around the coolant passages. Corroded areas can be identified by pressure testing the head. Corrosion of cylinder heads can be repaired by welding aluminum to the affected area.
To prevent overheating, make sure that your radiator is filled and in good conditions, with a tightly sealed cap. Check to be certain that your engine thermostat is in good working order, and accurately reflecting the temperature. Make sure that you have no leaky belts or stretched hoses, and that the fan is working effectively. If your car does overheat, stop, turn off the engine, and allow it to cool completely before adding water.
If your car has overheated, check the cylinder head and gasket for signs of cracking or warping. If the cylinder head has warped even slightly out a flush state, it will cause cylinder head cracking. In this case, the head gasket may need to be replaced and the cylinder head should be ground even again before it cracks.
Symptoms of a damaged cylinder head:
· White smoke: If excess grey / white smoke can be seen in the exhaust of the vehicle this is likely to be caused by the engine overheating which could be caused by a fault in the cylinder.
· Blue smoke: Excessive blue / grey Smoke is usually an indication of oil burning in the combustion chamber. This can be caused by leaking valve seals, excessive clearance between the valve stems and guides, worn piston rings or worn / distorted cylinder walls. These conditions can be repaired by re-bedding the valves or machining the cylinder walls.
· Leaking: If the vehicle is leaking coolant and there is no sign of any hoses or the radiator weeping, this may be a result of a cracked cylinder head.
· Smell: If the engine appears to be giving off excess odour this could again be a cracked or warped cylinder head allowing coolant to leak into the cylinders.