Exhaust Manifold Gasket
A high-temperature seal compressed between the cylinder head and the exhaust manifold, preventing dangerous exhaust gas leaks.
The exhaust manifold gasket is a high-durability seal compressed between the engine's cylinder head and the exhaust manifold. Its role is to seal the exhaust ports, ensuring that all hot exhaust gases exiting the combustion chambers are routed directly into the exhaust system without leaking into the engine compartment.
Because it sits directly at the engine exhaust ports, the exhaust manifold gasket is exposed to extreme temperatures (exceeding 1,200 degrees Fahrenheit) and raw combustion pressures. It is typically constructed from layered steel, graphite, or copper to withstand these conditions and accommodate the thermal expansion and contraction of the exhaust manifold.
If the gasket fails or blows out, hot exhaust gases will escape under the hood. The most recognizable symptom of a leaking exhaust manifold gasket is a loud, ticking or tapping sound coming from the engine bay, which is most noticeable when the engine is cold and often fades as the metal heats up and expands to temporarily seal the leak. Other signs include exhaust smells inside the cabin and soot deposits around the manifold ports.
A leaking exhaust gasket is a safety hazard, as it can release toxic carbon monoxide gas into the cabin heater intake. It can also allow fresh air to enter the exhaust stream, fooling the oxygen sensor into reporting a false lean condition, which causes the engine computer to inject excess fuel. Replacing the gasket requires unbolting the manifold, cleaning the mating surfaces, and installing a new gasket.