Auto Talk: Smoke Signals

© Stefan Redel

Smoke coming out of your vehicle’s tailpipe is often a bad sign. Exactly how bad it is depends on the color of the smoke.

Blue smoke
This normally means that you have some engine wear or damage. When damage allows even a small amount of engine oil to get into the cylinder area, that oil will burn, producing blue smoke from the tailpipe.

“A steady stream of blue tailpipe smoke suggests that oil is entering the combustion chambers and burning, causing diminished oil pressure and decreased catalytic converter efficiency,” says Mike McCracken, service advisor at Mountain View Garage, a AAA-approved repair facility in Thornton.

The problem could be caused by a cracked or leaking seal, a clogged oil line or various other situations. It is safe to drive the car, but take it to a technician as soon as possible so the problem can be fixed. If enough oil leaks into the cylinder, it will start to affect the spark plug, and the cylinder will misfire. Some initial home remedies include cleaning or replacing the spark plug, using thicker oil, or thickening the oil with an additive. These quick fixes should not be used long term.

Black smoke
Black smoke from the tailpipe means that there is too much fuel in the fuel-air mixture that is burned in the vehicle’s cylinders. The smoke will smell like fuel, and often there will also be a noticeable decrease in the vehicle’s performance and fuel economy.

“Black smoke from the tail pipe is an indication of an engine running too rich,” says Bob Howell, owner of Bob’s Towing and Repair, a AAA-approved repair facility in Estes Park. “When an engine runs rich, the unburned fuel can wash the oil off of the cylinder walls, causing premature engine wear.”

If the smoke occurs only briefly when you start the vehicle, then goes away, there is no need for action. It’s normal for an engine to run less efficiently when starting up. However, if the black smoke continues while you drive, something is wrong.

There are many possible reasons why too much fuel might be getting into the cylinders. The trouble might be in the fuel pump, the injectors or elsewhere. In addition to finding and fixing the underlying problem, it will probably be necessary to drain and change the oil if it has been contaminated by leaking fuel.

To see if the oil is contaminated, look at the color of the oil on your dipstick. Contaminated oil will be discolored—brown or milky looking. If you see this discoloration in your engine oil, do not attempt to start the engine, not even to drive to a technician, as it may cause serious damage. Call for a tow instead.

White smoke
White “smoke” is steam. A small amount of thin, clear steam when starting the car on a cold morning is nothing to worry about: normal condensation causes this, often along with some drips of water from the tailpipe.

If you see thick white smoke coming from the tailpipe, it is the result of water and/or antifreeze from the cooling system entering the engine. You might have a failed head gasket, a damaged cylinder head or even a cracked engine block. If you find your coolant needs topping up more often than usual, be suspicious of a leak and seek the advice of a technician, even if you are not seeing white smoke.

“That prominent trail of white steamy smoke that you see from your tailpipe is no doubt due to antifreeze leaking into your combustion chamber and being vaporized,” says Marvin Hatton, owner of Valley Performance Inc., a AAA-approved repair facility in Monte Vista. “Stop immediately, call for a tow, and have the concern diagnosed, before further engine damage occurs.”







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