Head Gasket
The head gasket is the largest seal in the car engine. It seals the joint between the engine block and the cylinder head, keeping dozens of cylinders and channels from leaking into each other. A gasket failure, often called a gasket blowout, is usually caused by the failure of another component that causes the engine to overheat. Replacing the gasket is a difficult task that requires the removal of the cylinder head and its many parts. While the gasket itself is inexpensive, the overall cost of replacing it is high because of the work required.
Inside the engine are several cylinders that contain the pistons. These cylinders are surrounded by many narrow passages through which the oil and coolant move around the engine. The cylinder head is designed to be removed from the top of the engine so that the pistons can be accessed for servicing. The head gasket is essential in preventing oil and coolant from leaking into the cylinders, and also for maintaining the pressure inside the cylinders. A telltale sign of gasket failure is steam or blue smoke coming from the exhaust. This indicates that water or oil is leaking into the cylinders and being turned into vapor by the heat.
The head gasket is easily recognizable from all the other engine seals. It has the same length and width as the cylinder head but is only a few millimeters thick. In the center of the gasket are several large holes for the cylinders. Surrounding these holes are many smaller holes for the oil and coolant passages, as well as the holes for the cylinder head bolts. The head gasket is fragile and care must be taken when handling it, because one tear between any of the holes will ruin it. For this reason, the gasket should not be removed from its package until it is ready to be used.
The three main types of head gasket are multiple layer sheets (MLS), copper, and composite. Most car engines use the MLS gasket which is made from three steel plates laminated together and coated with synthetic rubber. MLS gaskets perform better than any other gasket types, as long as they are installed correctly. Copper gaskets are very durable but are only used on high performance engines, because they do not compress and the engine surfaces must be perfectly flat. Composite gaskets are an outdated type that were made from asbestos or graphite. Gaskets made from asbestos should not be handled because of the serious health risks associated with that material.
Changing a head gasket is not an easy task and it may be worth the cost of having it done by a professional mechanic. It takes a lot of time to remove all the engine parts just to get the gasket out, and it often takes much longer putting them back again. The intake and exhaust manifolds need to be removed, along with the valve train and cylinder head. Engines that use a fuel injection systems may also have wiring that needs to be disconnected from the cylinder head. Both of the engine surfaces need to be throughly cleaned and inspected before the new gasket is installed. Finally, all the bolts must be tightened with the correct torque, as specified in the service manual.
Head gasket failure is a serious problem that can be avoided with minimal effort. The escape of hot gases reduces engine performance and can damage other engine components, and the leaking of oil and water into the exhaust can also ruin the expensive catalytic converter. Gasket failure is usually caused by overheating or improper combustion. The simple way of avoiding gasket failure is to keep the engine properly maintained and not operate it above its limits. Keep the engine tuned and replace the drive belt, timing belt and water pump at the specified times. This will ensure that the head gasket lasts for many years.
