White smoke from exhaust after car is off?

[townha99]

Hey everyone,

First off, to the mods, I don't know if I'm even allowed to make a post like this so feel free to remove it if deemed necessary, or move it. Sorry for potentially causing a problem.

To my question:

My dad's E-Class was out on the driveway today after he got back from work and it had been off for about 20 seconds. There was some white smoke coming out of the right exhaust pipe, but not the left. I was just wondering if anyone knows whether this is just condensation or whether its a bigger problem like a blown head gasket/coolant leak or something else. I really can't put a finger on the smell, it almost smelled like something was burning. I didn't really think it smelled sweet, which is what makes me think its not a head gasket. It hasn't done this before to my knowledge. Any replies are appreciated! Thanks!

-Tony

 

[LM7325]

Probably just a little steam from water boiling. The Catalytic Converter produces water as it works, you can see it running out of the pipes of cars sitting in traffic. Nothing to worry about I think.

 

[FoRiZon]

Indeed its from the water evaporation inside the exhaust. But i have to ask. Is your weather when you driving cold or wet? Big contribution to that.

 

[townha99]

Indeed its from the water evaporation inside the exhaust. But i have to ask. Is your weather when you driving cold or wet? Big contribution to that.

It was cold, about 50ºF and around 75% humidity.

 

[FoRiZon]

It was cold, about 50ºF and around 75% humidity.

Theres your answer. The white smoke is caused by the temperature difference between inside which is hot and outside which is cold. The heat then comes out on any holes and also conductors like exhaust metal and cars hood.

The exhaust one is most visible due to the original purpose for letting out the engine waste and thus designed as such.

 

[CSLACR]

It's when the exhaust doesn't smell like it's burning that you have a problem.
Also many cars with duel exhaust fake it, which causes a "preferred" side that receives more exhaust flow, often the right side.

 

[FoRiZon]

It's when the exhaust doesn't smell like it's burning that you have a problem.
Also many cars with duel exhaust fake it, which causes a "preferred" side that receives more exhaust flow, often the right side.

Might be relevant. In GT6 there are numerous cars that has dual exhaust but only one of them (mostly right) that is actually pops. Is that actually true IRL?

 

[Blood Eagle]

Catalytic converters do not produce water as they work. What you see first thing in the morning with water and steam coming out of tailpipes is condensation due to parking a car with a hot exhaust for long periods of time. When you park a car after you've driven it the hot exhaust will suck in atmospheric moisture and trap it in the exhaust. As it gets warmed up again, condense that and steam would be the byproduct until it gets evaporated. On humid days you will see this more noticeably as well as condensation out of the air conditioner. White smoke is steam so it's either just normal condensation or something like coolant being burned in the combustion cycle which would be a problem like a blown head gasket. If it had a blown head gasket, it would be low on coolant and/or coolant mixed in with the motor oil which would appear a creamy type of color on the dip stick. I'd bet it was a short trip after the car had been sitting for hours and the condensation was not fully evaporated.

 

[CSLACR]

Might be relevant. In GT6 there are numerous cars that has dual exhaust but only one of them (mostly right) that is actually pops. Is that actually true IRL?

A lot of cars run a single pipe down either the left side, middle, or right side. (I believe the right side is most common, the middle is unavailable on any rwd or awd)
At the rear of the car the exhaust hits a "Y" pipe or sideways muffler, and the exhaust doesn't distribute equally between the split, it stays a preferred path that the bulk of airflow travels.
You can usually feel a difference in air mass and velocity at idle, by putting your hands at the tailpipes. (the right side usually has more air coming out)

 

[Bakemono36]

White smoke is usually caused by water somehow in the exhaust system. It could be a symptom of a blown head gasket but unless the oil looks milky, I wouldnt worry about that.

 

[townha99]

It's when the exhaust doesn't smell like it's burning that you have a problem.
Also many cars with duel exhaust fake it, which causes a "preferred" side that receives more exhaust flow, often the right side.

Yeah, I've seen that a lot. I was behind an X5 in traffic one day, and there was only condensation smoke from one pipe. However, our E does have two real exhaust pipes. I feel like the fakes have become increasingly common in recent years.

 

[townha99]

I'd bet it was a short trip after the car had been sitting for hours and the condensation was not fully evaporated.

Right on. It had been warmed up fully earlier in the day, but was only driven for 10 minutes in the evening.


Sorry for the double post

 

[LM7325]

Catalytic converters do not produce water as they work.

Yes they do. While it is not a waterfall mind you, it is vapor. It adds to the pipe condensation. Cars without a cat-con have less pipe condensation.

 

[Blood Eagle]

Yes they do. While it is not a waterfall mind you, it is vapor. It adds to the pipe condensation. Cars without a cat-con have less pipe condensation.

I guess we need to clarify the argument. Yes, condensation happens in exhaust systems hence the steam and water. What I was saying is that condensation in exhaust systems is caused by hot exhausts drawing in atmospheric moisture as they cool. If you take what you said in the literal sense, your diagram suggests that catalytic converters create their own water. This is untrue. When atmospheric moisture is present, it will condense when heated. The cat will not condense moisture if there is none. That's why exhausts steam first thing in the morning before it burns off. I understand your argument, I don't think you are implying that cats make their own water with no outside elements. I feel we are arguing the same point without paying attention to what eachother mean.

 

[LM7325]

I did not mean to come across as arguing. What a converter does is quite literally "convert". Through the catalytic process Hydrocarbons, Carbon Monoxide, and NOX are broken down and the products "produced" are water vapor, carbon dioxide, and nitrogen gas.

No, they do not make water. Produce was the best way I could come up with describing what is happening.

 

[Swagger897]

Aside from all this watery nonsense, if it were to be a remotely plausible idea that the head gasket is kaput, you would notice overheating for a long... long time, or at least running higher than normal in the looming days.

 

[Danoff]

If there's not a lot of it, white smoke (better known as steam) and blue smoke (burning oil) might look fairly similar. If you think you might have smelled burning oil, just get under it and look around for fresh oil.

 

[LM7325]

All this just reminded me of working at the Ford dealer as an intern while taking automotive classes. This was late 1998. We had a woman come in with a brand new 1999 Mustang GT complaining of white smoke first thing in the morning. Of course nothing was wrong but I had, just had to go test drive it. Hey it was a big deal in '99 and it was a 5 speed. I had to be sure it was ok lol. Lets just say I got it all warmed up for her...

 

[CSLACR]

And yet you would be pissed if you saw a mechanic treating your car like that.

 

[LM7325]

Oh I didn't try to hurt it. I just put it through the paces is all. The salesmen were much harder on them fresh off the transports. Never understood their logic really.

 

[townha99]

Thank you everyone for the responses! Not only did I get and answer to my question, I also learned some new things.