White exhaust smoke on cold start

[BADCLOWN]

My 2017 cement pro with 41k miles has the following happen:

I noticed a few days ago when the truck was started up (cold start) that white exhaust smoke was coming out the back. The temps outside were above 70 degrees and the smoke I would say was coming out the exhaust tip roughly 8-10inches before disappearing. I have noticed this occurring in the past when it hasn't been cold outside as well.

I thought I remembered threads posted about this a while back, but searched this forum section and couldn't find anything.

Has anyone experienced this or know what causes it? should I be concerned?

The only engine mod is a URD MAF box programmed for a stock intake. Engine runs normal, regular oil changes every 5k miles, never had a single mechanical issue since ownership at 12k miles.

Any insight would be greatly appreciated.

 

[Dynamo]

Sounds like it's just condensation inside your exhaust system burning off, which is normal and not an issue. Atmospheric conditions are probably just right to form condensation inside your exhaust system when it cools down. I assume it goes away after the engine warms up?

 

[BADCLOWN]

Sounds like it's just condensation inside your exhaust system burning off, which is normal and not an issue. Atmospheric conditions are probably just right to form condensation inside your exhaust system when it cools down. I assume it goes away after the engine warms up?

Yes, it does go away. I have just never experienced this on any of my previous vehicles (12-14 VWs, 3 BMWs (1 currently owned), and this 5th gen is my 4th Toyota (2 3rd gens and a TT FJ))

 

[ArthurKotb]

Worst case, it could be antifreeze burning off. If that were so, the inside of your exhaust pipe would be white-ish instead of gray-black. Cool damp morning air (note the humidity level of the air) mixing with the fuel is most likely the cause. You probably notice it more on rainy/foggy days than blue-sky dry ones.

 

[osugsxr]

take it to the dealer something is wrong.....,. :flamethrwoer2: .......did you do a scan for codes

 

[wsu_runner]

Years ago I saw similar behavior with a prior generation (3.0 V6) version of the engine. The problem ended up being due to a head gasket issue, which that engine was known for. Small amounts of coolant were finding their way into the cylinder and vaporizing upon combustion. The problem would typically subside as the engine heated because both head and block would expand once they warmed up.

Given the age of your vehicle I doubt it is the problem but if you want to rule it out you can perform a compression check on each cylinder to see if any are low.

 

[Charles Bronson]

99.9% sure this is water condensation from the cat light off and moisture that forms in the exhaust pipe as temps and humidity changes throughout the day. Most every car will have some level of condensation or "white smoke" on a cold start. My BMW M235 does it, my wife's 2020 4Runner does it, and my son's 2015 Outback does it. The fact that this only happens on a cold start and goes away quickly points to condensation.

 

[chrisridebike8]

It could also be oil from the PCV system. My C63 would do that. If you don't have a catch can, then oil is recirculated from the crank case to the intake and sometimes a little buildup decides to burn off during start and will give you a lot of smoke. I wouldn't worry about it.

 

[Jetboy]

Never saw it on my 4runner. But my Tundra has a ton of it for some reason below about 45 degrees. Probably depends on how it was driven before turning it off as well. The 3 way chemistry in the cats converts nox and o2 into CO2 and water vapor. The water vapor leftover from the last drive tends to condense inside the exhaust when the muffler is cold and the warm humid air is inside from driving. Catalytic converters have a lot of surface area to condense water. Then you start it and you also get a big initial shot of fuel to start the catalytic reactions and a bolus of water vapor together with the condensed water in the exhaust evaporating out. So it's probably a few sources that combine.

If your coolant isn't dropping I wouldn't worry about it. If it is dropping you kinda know the issue at that point. Look at any tundra cold Start video on YouTube and they all do the same thing. I was concerned at first on mine but seems to be normal.

 

[jbooth07]

I’m having the same issue with my 18 T4R with 120k miles. Doesn’t happen all the time but when it does it’s a fairly large white cloud. Atmospheric temp ranges from 55-80 degrees. This afternoon was 78 with 24% humidity (not sure if pertinent) and the cloud was the largest I’ve seen.

Potentially unrelated, the vehicle has been idling noticeably rough and at times the RPMs fluctuate ~200-400 especially when it’s hot out.

I have an appointment at a local Toyota shop next week but wanted to see if the interwebs had any insight.


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[Whippersnapper02]

I’m having the same issue with my 18 T4R with 120k miles. Doesn’t happen all the time but when it does it’s a fairly large white cloud. Atmospheric temp ranges from 55-80 degrees. This afternoon was 78 with 24% humidity (not sure if pertinent) and the cloud was the largest I’ve seen.

Potentially unrelated, the vehicle has been idling noticeably rough and at times the RPMs fluctuate ~200-400 especially when it’s hot out.

I have an appointment at a local Toyota shop next week but wanted to see if the interwebs had any insight.


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If the engine was burning coolant, you would smell it. Also the level would be going down.

 

[seatia]

I’m having the same issue with my 18 T4R with 120k miles. Doesn’t happen all the time but when it does it’s a fairly large white cloud. Atmospheric temp ranges from 55-80 degrees. This afternoon was 78 with 24% humidity (not sure if pertinent) and the cloud was the largest I’ve seen.

Potentially unrelated, the vehicle has been idling noticeably rough and at times the RPMs fluctuate ~200-400 especially when it’s hot out.

I have an appointment at a local Toyota shop next week but wanted to see if the interwebs had any insight.


Sent from my iPhone using Tapatalk

The rough idle can be alarming.
The dealership can pressure test the cooling system.
An old shade tree trick was to wipe a finger inside the tail pipe and taste it for sweet, if so, it's coolant and a leak.