If you see water dripping or steam floating from your tailpipe there is probably coolant entering the combustion chambers. Antifreeze is run through the engine block to cool the engine. If coolant is making its way into the exhaust, a leak or crack are the only possible causes. A process of elimination is the best way to determine the cause and to get your car back to running order.
Detecting the Problem
Start your car and let it idle for a few minutes. Observe the white smoke and water escaping from the tail pipe. If white smoke starts to escape immediately, water begins to drip as the car warms up, and your exhaust smells of antifreeze, there is a coolant leak inside your engine. Perform two final checks by opening your radiator (when cool) and look for oil floating on the water, and pulling your dipstick and looking for a milky emulsion (antifreeze mixed with the oil) on it. These are both clear signs of a coolant leak.
The smoke escaping from your tailpipe is actually steam and will appear more grey than white in colour if examined closely. The water is the result of an accumulation of that same steam as it makes its way through the exhaust system and out of the tailpipe where it condenses from its gas form back into liquid.
Head Gaskets are Often the Cause
A faulty head gasket is the most common cause of such coolant leaks, and is the cheapest to fix of the possible problems. If the replacement of the head gasket fixes the issue, then no further action is required. The gasket is a low-cost piece which lays between the head and the engine block, creating a seal. Although it may seem an insignificant item when you see it up close, this is an essential part of the engine and can very well be the cause of your troubles. Your mechanic will be able to confirm a coolant leak with a coolant system pressure test. If the cooling system won't hold pressure, this indicates an internal leak.
Testing your engine compression is the next logical step in the process of solving the problem. If the compression is low you may have one of three problems. There may be a crack in the head or in the block. Each of these potential causes can mean costly repairs. Your mechanic will be able to perform a series of tests on your engine to eliminate each of these as the cause and settle on which is the culprit. Have your mechanic test your engine block and head for cracks. If there is a crack in the block or head, repairs are sometimes possible but you may have to replace the engine. Cracks are caused by faults in the metals which make up the block and or head. These defects in the metal are undetectable by the car owner until the crack occurs and are a result of the casting process during manufacturing. Cracks can also be caused by the use of incorrect parts or the incorrect installation of parts, or by putting cold water into an overheated engine.
Bad piston rings can also be a cause of whitish-blue smoke in your exhaust, but in this case the smoke is produced by oil and not coolant. Rings are as they sound, ring-shaped pieces of metal which sit in the head of each piston creating a seal against the cylinder wall as it works its way up and down the cylinder. These rings can wear over time. When excessively worn, the rings will allow motor oil to seep into the combustion chamber and from there, the exhaust. If rings are an issue, they can be changed without any harm done to the rest of the engine, although it is expensive in terms of labour.