Why Gaskets Are Important In an Engine

Fluids such as oil and coolant need to circulate inside an engine. To ensure they don’t leak out, engines are fitted with gaskets, which are metal, paper, silicone, or composites cut to match the surfaces between which they are sandwiched. They are used to prevent leaks by sealing the gaps between connected surfaces.

Older engines had gaskets made of special paper, and, in situations where hot exhaust flows from a cast iron component into an aluminum component (such as EGR or other exhaust), the gasket will be a thick, tough semi-metallic design coated on both sides with graphite to prevent the different expansion/contraction rates of the metals from destroying the gasket.

Older engines had gaskets made of special paper, and, in situations where hot exhaust flows from a cast iron component into an aluminum component (such as EGR or other exhaust), the gasket will be a thick, tough semi-metallic design coated on both sides with graphite to prevent the different expansion/contraction rates of the metals from destroying the gasket.

–Richard McCuistian, ASE Certified Master Automobile Technician

What Does a Gasket Do?

Gaskets in cars play a critical role in keeping oil and coolant contained in their corresponding pressurized channels.

Oil flows around many moving components such as the crankshaft and valvetrain, keeping those parts lubricated. Meanwhile, coolant flows inside channels around the engine block, taking heat away from the cylinder head and the cylinder walls. It absorbs the heat and carries it to the heat exchanger we call the radiator. While these fluids flow in close proximity to one another, they should never mix because they serve very different purposes and flow through different components.

Gaskets function similarly to seals and they only differ in how they’re constructed. Unlike seals, gaskets are made into different shapes so they can fit around the flat surfaces of two components.

Engine gaskets need to be strong and heat resistant because there can be a lot of heat and pressure during engine operation. The gasket passages where coolant leaves the head and travels to the engine block are much smaller than the corresponding ports in the head and block so as to slow the coolant and allow it to absorb heat effectively.

Because of the immense heat and pressure, head gaskets aren’t made from flexible materials like rubber. Instead, the head gasket is made from several layers of different types of steel.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: When parts are being replaced, the parts of the old gasket must be totally removed using a proper scraper, followed by gentle sanding, using a good light that can be shined across the surface at an angle to make sure none of the old gasket remains.

What Are the Gaskets On Your Engine?

There are several gaskets around the engine that keep fluids contained in their corresponding channels.

Head Gasket

As previously mentioned, the head gasket sits between the cylinder head and the engine block and essentially seals the top and bottom halves of the combustion chamber. Aside from keeping oil and coolant in their respective channels, the combustion chamber also prevents hot gases from the combustion chamber from escaping. The head gasket is an extremely important engine component and head gasket leaks can result in serious engine problems.

Valve Cover Gasket

The engine’s valvetrain sits on top of the cylinder head and it controls valve operation. These valves precisely control how air enters and exits the combustion chamber.

One of the valvetrain’s components is the camshaft, which is a long metal rod that has several metal grooves along its length called cam lobes. As the camshaft spins, the cam lobes press on the pushrods, which in turn open the valves inside the engine. The lobes can hit the pushrods thousands of times a minute, so valves need to be constantly lubricated so that the cam lobes and camshaft don’t wear out from the friction from their contact with each other.

The valve cover gasket seals the cylinder head and the valve cover. Hot, pressurized oil flows inside the valvetrain so the valve cover gasket needs to withstand the heat and pressure to keep everything in place.

Oil Pan Gasket

The oil pan gasket sits underneath the engine, allowing oil to accumulate and cool before it’s recirculated back into the engine. The oil pan gasket simply seals the gap between the engine and the pan. Much like the valve cover gasket, the oil pan gasket needs to withstand heat from the oil as it comes down the engine. Some engines use RTV silicone from a tube as an oil pan gasket.

Timing Cover Gasket

The timing cover is usually between the water pump (or around it) and the engine block, with the timing chain just inside. The timing cover gasket sits between the timing cover and the engine block, providing a seal to keep oil in and foreign materials like dirt and water out.

Intake Manifold Gasket

The intake manifold is connected to the cylinder head, and between the two sits a mechanical seal called the intake manifold gasket. The intake manifold is in charge of channeling air and sometimes fuel to the cylinder head. The intake manifold gasket is a flat seal that sits between the intake manifold and the cylinder head. It ensures that air and fuel are contained within the two previously mentioned components.

Exhaust Manifold Gasket

The exhaust manifold gasket is a mechanical seal that sits between the exhaust manifold and the cylinder head. Unlike the intake manifold gasket, which prevents fresh air from the intake from escaping, the exhaust manifold gasket prevents hot gases from the combustion chamber from leaking. The exhaust manifold gasket can either be steel or, in some cases, a composite asbestos or aramid-type material that’s heavily coated with slippery graphite to handle the “scrubbing” effect created by the repeated expansion and contraction of the steel exhaust manifold and aluminum cylinder head.

While engine gaskets are strong and heat resistant, they can wear out and require replacement after several years of use. Gaskets might be relatively simple components but you shouldn’t hesitate to have an inspection if you think they’re faulty. Broken gaskets can ruin your engine and require a complete engine rebuild, which is expensive and time-consuming. Always look out for the symptoms of faulty gaskets and have them inspected at the first sign of trouble.