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AUTO ADVICE: White smoke might be a moisture problem

Question: I hope you can give me an idea about what might be making my Nissan van smoke white smoke out the tail pipe when you crank it cold. I bought the van about four months ago. After I got it home it started running bad and white smoke was c...

Question: I hope you can give me an idea about what might be making my Nissan van smoke white smoke out the tail pipe when you crank it cold. I bought the van about four months ago. After I got it home it started running bad and white smoke was coming out the tail pipe when cranked cold. I took the van to a Nissan dealer they said for me to call the Dodge dealer where I bought the car because it had problems.

The Dodge dealer took it to a different Nissan dealer, who said the motor was locked up. Somehow, after this, the motor is no longer locked up. The mechanic discovered that the catalytic converters were bad. He replaced them, drove the van some distance, and it stopped smoking. The car drives great now. How could the motor have been locked up and then not? About a week after we got the car back it started smoking out the tail pipe again when cranked cold. The van drives wonderful and does not miss or anything.

I hope that you give some suggestions about what might be making my van smoke. After being told that the motor was locked up I just don't know what to believe. Your suggestions will be greatly appreciated.

Answer: Wow! This is quite the puzzle, due to the number of chefs in the kitchen and multiple counts of lousy communication. In areas or seasons of high humidity, it's normal for a vehicle to produce some white smoke during engine warm-up, due to moisture condensation within the exhaust system. If you're noticing a large quantity of white smoke during cranking or immediately after startup, I'd suspect a leaking head gasket. In this case a void in the head gasket allows a small quantity of engine coolant (under pressure as the engine was previously shut off) to sneak into one or more of the engine's cylinders. Upon startup, the coolant is vaporized and passes through to the exhaust. This might also explain the one time engine "lockup." Liquids are not compressible, so if a large enough quantity of fluid entered a cylinder, it may prevent the piston from reaching the top of the cylinder as the engine is cranked. This is a little scary, as the opposing forces can bend the connecting rod or break the piston. A more severe (soon to come) head gasket leak leads to engine overheating and a strong engine miss.

A slight head gasket leak may also result in a cylinder misfire for a moment or longer at startup. I wonder if the catalytic converters were found to be plugged (the internal honeycomb broken apart, causing a substantial exhaust restriction). This could make the engine run very poorly (generally smooth but a severe lack of power), and possibly run hot enough to finish off a marginal head gasket. Cat failure of this type usually results from a frequent or continuous engine misfire.

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My hunch is the selling dealer may have added a head gasket remedy (mechanic in a can) to the coolant, in an attempt to correct the failure, and it worked for a while. I'd insist on having a head gasket test performed -- this consists of a check for carbon monoxide, exhaust hydrocarbons, or bubbles in the cooling system. Another trick is to remove all the sparkplugs and watch for a small gusher of liquid from any of the cylinders as the engine is cranked.

Is the selling dealer willing to make the van truly right (possibly an expensive fix)? Strike now, while the iron is hot!

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