As gaskets go, the head gasket is probably the most important within a car.

Its job is to seal the combustion chambers and the coolant and oil passages between the engine block and the head. These are very important areas to keep sealed and apart from each other as the combination of unwanted coolant entering a cylinder or the oil supply is a recipe for disaster. 

The head gasket is under the most intensive pressure of any vehicular gasket and if this tortured component fails, it could spell catastrophe for your car, so material choice is critical. A modern head gasket therefore is generally designed to never fail or need replacing, with the long bolts of the engine block squeezing it in place to a desired tolerance. This doesn’t mean that it can’t fail, with lack of proper maintenance, excessive engine stress and engine modifications among the main reasons for failure.

7 Ways A Head Gasket Can Fail

If a head gasket were to fail, different levels of engine damage can occur depending on how the head gasket fails. No failure will be inexpensive to fix, with the cost of labour being the main expense in most cases

• Coolant to outside leak If a head gasket fails between a water passage and the outside of the engine, the cooling system will eventually run low on coolant. When the coolant level drops too low the engine will overheat

• Compression leak to oil galleries This will allow the piston to suck oil into the cylinder, where it will be burned off as part of the combustion process. This will eventually cause a drop in engine oil levels, and will also cause blue smoke from the exhaust from burning oil

• Water to oil leak If the head gasket fails between an oil gallery and a water passage it will allow the engine oil and coolant to mix, resulting in contaminated oil and compromising the cooling system

• Oil to outside leak This one is fairly easy to spot, and if the head gasket fails between an oil gallery and the outside of the engine you will be able to see the oil leaking down the engine. While not as immediately dangerous as other types of head gasket failure it will still require repair as it will only get worse over time

• Compression leak to coolant If the head gasket fails between the cylinder and a water passage it will allow exhaust gases to enter the cooling system, resulting in overheating. This, in turn, can result in damaged cooling system components. It can also lead to damage in the catalytic converter as it exits through the exhaust system

Left: a blown gasket from a vintage bus. Right: Dobson’s reverse-engineered version

Types of Head Gasket Material

From our factory in West Yorkshire, we produce a range of gaskets designed not to fail,  including the all-important head gasket. The best material for a head gasket often depends on the specific requirements of the engine and the conditions under which it operates. However, some commonly used materials include:

Multi-Layer Steel (MLS): Known for its durability and ability to withstand high temperatures and pressures, MLS head gaskets are constructed from multiple layers of stainless steel with a polymer coating. They provide excellent sealing properties and are often used in high-performance engines.

Graphite: Graphite head gaskets are known for their flexibility and ability to conform to irregularities in the sealing surfaces. They offer good heat resistance and are often used in engines where thermal cycling is a concern.

Metals: Copper, traditional soft metals or composites are used for vintage automobile gaskets. Easily damaged during the production process, our highly skilled technicians precisely engineer them to maintain the integrity and lifespan of the seal.

Composite: Composite head gaskets are made from a combination of materials such as graphite, asbestos, or aramid fibres. They offer a balance of sealing ability, flexibility, and affordability, making them suitable for a wide range of engine types.

MLS with Rubber Coating: Some modern head gaskets combine the durability of MLS with a rubber coating for enhanced sealing properties. This combination provides excellent sealing under varying conditions and is commonly used in modern engines.

A Multi-Layered Steel Head Gasket

The Right Choice

Although certain specific situations may require different solutions, Multi-Layer Steel (MLS) gaskets are the go-to material of choice, being renowned for their robustness and reliability in sealing engine components. They are composed of multiple layers of stainless steel, typically three to five layers, each sandwiched with sealing material that creates a springlike effect to provide continuous sealing properties over various pressures. The surface of a head gasket must be completely smooth, as any unevenness, distortion or roughness can result in sealing failure.

The design of MLS gaskets allows them to effectively seal the cylinder head to the engine block, preventing leaks of oil, coolant, and combustion gases even under extreme temperatures and pressures. Their ability to maintain a tight seal over prolonged periods makes MLS gaskets a popular choice for high-performance engines and applications where durability and consistent performance are essential.

At Dobson's, we manufacture automotive gaskets to any specification, and our skilled technicians will be able to provide advice on the materials and design that will best suit your application.