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What Causes Water Dripping From a Muffler?

by Charlie Hare

When internal combustion engines run, the air and fuel combustion that takes place inside the cylinders releases moisture from the air, which generally gets sent out the exhaust system as water vapor or steam. If the engine and exhaust system are cold, moisture can condense from the steam to form a liquid that may drip out of the tailpipe.

Small Amounts

A small amount of moisture dripping from automotive exhaust is normal.

A small amount of water dripping from the tailpipe of a cold engine is normal, and should cause no concern. Some cars' exhausts might drip constantly if they are used only for short trips, as the engine and exhaust system may never get hot enough to prevent the exhaust moisture from condensing back to liquid. The biggest danger of chronic small amounts of water in the exhaust system is the possibility of rusting out the system prematurely. Many exhaust systems are made from stainless steel to prevent rusting.

Large Amounts

Many cars and trucks sometimes drip small amounts of water from exhaust pipes.

If there are large amounts of water dripping from the tailpipe, it can be symptomatic of a leaky head-gasket, which is a serious and costly repair. Usually, when head gaskets begin leaking, the exhaust plume becomes quite thick and light colored and may emit a sweet odor. This is produced by your engine coolant being boiled and exhausted from the combustion chambers. Seek mechanical help immediately.


Leaky head gaskets often allow engine coolant into the combustion chambers.

When the air is humid, more moisture may be present in automobile exhaust. Likewise, if the air is cold, some moisture may drip from the exhaust pipe until the engine and system get hot. If the amount of moisture dripping from exhaust pipes appears excessive, have a reputable mechanic look at the vehicle.

About the Author

Charlie Hare has been writing since 1970 for a large Fortune 500 company. Hare contributed to, compiled and published the quarterly "Facilities Flyers," which was distributed to over 300 employees, as one of his duties. He has submitted instructional content online since 2007, specializing in topics such as cars, home and garden, computers, and pets and animals. Hare attended Manchester Community College.

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