What Causes Water Dripping From a Muffler?

Written by charlie hare
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What Causes Water Dripping From a Muffler?
Exhaust "smoke" is really steam, or water vapour, unless something is seriously wrong. (exhaust fulmes image by bilderbox from Fotolia.com)

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 vapour 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 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.

What Causes Water Dripping From a Muffler?
A small amount of moisture dripping from automotive exhaust is normal. (exhaust flat image by DBarby from Fotolia.com)

Large Amounts

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 coloured and may emit a sweet odour. This is produced by your engine coolant being boiled and exhausted from the combustion chambers. Seek mechanical help immediately.

What Causes Water Dripping From a Muffler?
Many cars and trucks sometimes drip small amounts of water from exhaust pipes. (White sports car image by Christopher Dodge from Fotolia.com)


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.

What Causes Water Dripping From a Muffler?
Leaky head gaskets often allow engine coolant into the combustion chambers. (pipe: steam and smoke rise image by alma_sacra from Fotolia.com)

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