Symptoms of a Blown Gasket in an Exhaust Manifold

by Allen Moore
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The exhaust manifold gasket helps seal the union between the exhaust manifold and the side of the engine’s cylinder head. In cases where the gasket is not installed properly, or the manifold and gasket are beginning to deteriorate due to age, leaks can occur. Once the gasket is “blown,” a slang term for gasket failure, it should be replaced as soon as possible. Determining if an exhaust manifold gasket has failed is easy to do.


A blown exhaust gasket often protrudes from the gap between the exhaust manifold and the cylinder head. Visually examine the area where the manifold and head meet. If the engine is a V-6 or V-8, compare both sides. Odds are, not all the gaskets, or every portion of the gasket if it is a single unit, are blown. Look for pieces of gasket that are protruding far more than the rest which will indicate the point of failure. Another telltale visual sign is sooty exhaust which will stain the side of the cylinder head or manifold. These stains will resemble the staining that occurs inside the tailpipe. If the entire area is dirty, clean it off with engine cleaner then operate the engine for a day or two, as normal, before looking again. Follow this stain back to its point of origin to pinpoint the failed gasket.


Exhaust gas and noise are expelled from the engine at a high velocity, down through the exhaust manifold and into exhaust pipes, where they pass through the catalytic converter and muffler before exiting from the tail pipe. The purpose of the muffler is to reduce the audible sound of the exhaust gases leaving the engine. In the event your manifold gasket is blown, the exhaust gas will escape at the seal between the manifold and cylinder head, resulting in a loud bang or pop noise each time that cylinder fires. This noise can be commonly confused with an engine knock. The telltale difference in the two sounds is the slight hiss that precedes and follows the popping noise. If that hiss is present, chances are the exhaust manifold gasket has failed.


The purpose of the catalytic converter is to neutralize some of the hazardous exhaust gases before they are released into the atmosphere. Exhaust gases escaping the system prior to passing through the catalytic converter have a stronger odor than those that exit the tail pipe. If strong exhaust odor is present in the engine area, inspect the exhaust gaskets to see if one or more has failed and is now allowing the untreated exhaust fumes to escape into the engine well.

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