a little white smoke on cold start

[pasadena_commut]

The last couple of weeks my 03 P5 has been putting out a little bit of white or grey smoke when it starts cold. It's definitely smoke and not steam, and it does it on the first start even when the temp is fairly warm and there's no condensation on the car. After a minute or two, or once the car warms up,
which is about the same time, it doesn't smoke anymore. It runs fine aside from the smoke.

It may have started after the last oil change.

So far I've checked:

1. Coolant levels = normal.

2. No white or yellow crud under the oil filler cap.

(So it's probably not coolant getting into the motor, which fits since it's smoke and not steam.)

3. Oil level is a bit over F. Maybe the mechanic put in too much oil? Would that cause this symptom only when cold?

4. Put a white furnace filter over the tail pipe when my wife started the car cold. Ran it that way for a a minute. The smoke just blew through the filter and it left no mark on the filter at all. So whatever this stuff is it is probably not made up of little greasy oil drops.

The car only has a bit over 40K miles so valve wear (and oil from that dripping into the cylinder overnight) seems pretty unlikely.

Any suggestions what to check for next?

 

[falsedawn]

http://www.google.com/search?hl=en&q=white+smoke+from+exhaust

 

[Replica]

http://www.google.com/search?hl=en&q=white+smoke+from+exhaust

i guess theres no need for the mazda forum! Everyone go to google!

 

[kcbhiw]

There doesn't have to be condensation on the car to indicate that it's cold enough for steam. One of the bi-products of gasoline combustion is water. Since the exhaust pipe is cold upon start (assuming that you haven't driven the car for a few hours), the water vapor will condense on the inside of the pipe. Once the water droplets are large (heavy) enough, they will be fall into the exhaust stream and be expelled. When the exhaust piping becomes hot enough, the water no longer condenses and continues through the pipe as a vapor.

The same principle is witnessed on a damp or a cool and humid day with windsheild fogging.

All in all, I say it's condensation.

 

[DeadGeneration]

Or it could be too much nawz

 

[slkt]

My 5 has a lot of white smoke in cold weather....

 

[kcbhiw]

My 5 has a lot of white smoke in cold weather....

As do most other cars.

 

[slkt]

As do most other cars.

Yes

 

[pasadena_commut]

There doesn't have to be condensation on the car to indicate that it's cold enough for steam. One of the bi-products of gasoline combustion is water. Since the exhaust pipe is cold upon start (assuming that you haven't driven the car for a few hours), the water vapor will condense on the inside of the pipe. Once the water droplets are large (heavy) enough, they will be fall into the exhaust stream and be expelled. When the exhaust piping becomes hot enough, the water no longer condenses and continues through the pipe as a vapor.

The same principle is witnessed on a damp or a cool and humid day with windsheild fogging.

All in all, I say it's condensation.

There's no condensation on the outside of the car, so presumably none on the inside of the exhaust, and the smoke starts immediately upon startup. When do the water droplets have time to condense and fall into the exhaust stream?

Besides, this stuff just doesn't act like steam. Steam goes all whispy and dissipates rapidly whereas this stuff hangs in the air for a long time as if it were particulate (=smoke).

The P5 lives in the garage. Next weekend if it's still warm I'll try waiting until noon or so before starting it and see whether or not there's smoke. If the car has warmed up to 70 or so before starting and there's white smoke then presumably it's not condensation.