White Smoke from Exhaust - 2019 Crosstrek 64k Miles

Oct 10, 2022
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Hey all

About 3 months ago I started noticing a small white puff from my tail pipe every time I started my car. Then after being out of town for a month, I came back and upon start up the smoke came out a much bigger cloud, but subsided after about 10 seconds. I have noticed a small bubbling/gurgling sound from the engine bay just prior to the smoke coming out as well.

Took it into the dealership after the same issue occurring on almost every start up over the next few days, but they said they were unable to recreate the issue and that they found nothing wrong after a thorough inspection of the engine. Fast forward to now, I started it again after being away for 2 weeks and the smoke emitted was the most it had ever been. It did subside a bit, but didn't fully stop even after 5 minutes of running.

As for troubleshooting I've done:

- The oil looks good on the dipstick (it was changed about 6 weeks ago), there is no residue on the oil fill cap
- Spark Plugs were replaced 1yr/5k miles ago
- There are no leaks anywhere that I can see (on ground or on engine components)
- Coolant seems to have dropped a lot for 3 weeks (halfway between min&max), however that could just be fluctuation from temperature
- There are no warning lights or messages on the screens
- Vehicle hasn't been overheating or even getting close to
For cooler temps. and higher humidity moisture can be drawn into the exhaust system as it cools. This will come out of the exhaust as steam as the exhaust warms up. You could have a head gasket leak into a cylinder but the techs should have caught it. Does the white smoke have a strange smell? Does the coolant have a 'slick' floating on it?
"Coolant seems to have dropped a lot for 3 weeks (halfway between min&max), however that could just be fluctuation from temperature"

That is the key factor including the "bubbling/gurgling sound from the engine bay". The cooling system is now "aerated" and needs attention.
Have the cooling system pressure tested for any internal or external leaks.
The cooling system needs to be filled, have the air bled out and needs to remain under pressure.
A cooling system that is not leaking will not drop the pressure reading of the tool.
The test is accomplished at ambient temperature. The spark plugs need to be removed for that test.

An even smarter technician will attach a pressure sensor / transducer onto the radiator cap and measure the pressure pulses with an oscilloscope. That test will definitely prove which cylinder is pushing compression gases into the cooling system.
At times, the leak will be more evident cold. the coolant will leak into the combustion chamber / burn off and create the "smoke".

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