Article > Feature Story

ASE P2: Exhaust Parts

By Larry Carley

All vehicles have at least one or more mufflers mounted aft of the catalytic converter.
Most late-model vehicles come factory-equipped with long-life stainless steel exhaust systems, but eventually most exhaust pipes and mufflers fail and need to be replaced. Exhaust leaks are noisy and increase the risk of carbon monoxide poisoning.

All vehicles have at least one or more mufflers mounted aft of the catalytic converter. A second muffler or resonator may be located further back for additional sound control. Vehicles with dual exhausts usually have separate mufflers for each side, but some may share a common muffler.

Mufflers most often fail from the inside out due to corrosion caused by the acids and moisture in the exhaust gases. Mufflers mounted behind the rear axle typically have shorter lives than those mounted closer to the converter because they run cooler and collect more moisture.

Replacement mufflers come in various types. Direct fit replacement mufflers look and install the same as the OEM muffler. Universal mufflers fit a wider variety of applications and may require adapters to install. Performance mufflers use fewer baffles and restrictions, or have a straight through design and/or flow straighteners to reduce backpressure for improved power and fuel economy. The trade-off may be increased exhaust noise — which some customers want.

Exhaust pipes include the head pipe that connects the exhaust manifold to the converter, the y-pipe that connects the right and left sides of a V6 or V8 engine into a single exhaust, the exhaust pipe, which connects the converter with the muffler, and the tailpipe which usually extends aft of the muffler or resonator. Some FWD cars have a flexible head pipe to accommodate engine vibrations.

Special exhaust tools may be needed when replacing pipes or mufflers. These include pipe cutters and pipe chisels for separating corroded pipes and connectors, and expanders for repairing or installing new pipes and mufflers.

Other items that may be needed when replacing exhaust pipes include new clamps, pipe hangars and heat shields. Clamps must match the diameter of the pipes. Heat shields should be replaced if damaged, corroded or missing.

Exhaust manifolds carry hot exhaust gases away from the engine. Bolted to the cylinder head(s), the exhaust manifold(s) connect to the head pipe or Y-pipe. Most are cast iron, but some are welded stainless steel tubing. Some exhaust manifolds also include “pre-cat” converters to reduce cold start emissions. Cast iron manifolds can sometimes crack, causing a loud exhaust leak. New exhaust manifold gaskets are required when replacing an exhaust manifold.

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