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2015 Forester 2.5i CVT Limited - TR580/FB25BC
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Discussion Starter · #1 ·
Hit the gas hard from a slow speed, about 10mph, and got up to about 5000 rpm and noticed a cloud of white smoke coming out of the tailpipe. Did some looking on this site and saw some comments related to the Turbo engines but nothing on non-turbos that fit my circumstances.

Tried to replicate it while hitting the gas hard at about 20mph and getting it up to 5000 rpm again. There was a little smoke but nothing compared to the first time.

First, I never drive the car like this. Mostly never get it above 3000 rpm - no need.

I stopped and checked the oil to see if there was any white foam on the dipstick - thinking it could be a coolant leak but didn't find any. The oil level is right at the top dot. I did add 5oz of Lucas oil additive during the last Oil/Filter change, but compensated by only adding 5qt of oil.

No Oil light on in the car.

The other thing is I have been noticing a low crackling/sputtering sound on normal acceleration, but it seems to only happen when the rpm is dropping and I hit the gas a little. So, on acceleration after coasting.

Could this just be a super hot engine burning off carbon deposits?

I have added some fuel additives in the past but not on this tank. It was nearly empty when I refilled with Kirkland Top Tier Regular this week.
 

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2015 Forester 2.5i CVT Limited - TR580/FB25BC
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Discussion Starter · #5 ·
Possibly just steam from condensation in the exhaust boiling off. How long had you been driving the car before this happened?
I had driven it for about 50 minutes 25-55 mph, parked the car for about 30.

You are making a mistake not driving hard once in a while.
I feel like that too, but don’t do a lot of highway driving. Mostly city streets.
 

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2017 Forester 2.5 Premium, Black
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Does not seem like a head gasket problem which will produce water vapor / steam. I am guessing a high mileage engine with valve stem seal wear. It is common for oil to leak past these seals and build up when the engine is loafing (like going slow, going downhill, or at a long stoplight). Then when you get on it the excess oil burns off producing a blueish white smoke. If it were worn piston rings, it would smoke continuously. You probably are down more than one quart at oil changes. You might want to consider thicker oil like 10w/30. You can get a Leak Down Tester at Harbor Freight.
 

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@johnnyjackhammer -- Ther IS a need to run hard once in a while, as @abc states. By babying the car, a disfavor towards the vehicle is being made.

I've had to break-in a few 'Granny's Cars' to the highway in the past. You know -- the cherry car that granny never drove more than just to get to church and the grocery store. And others have blown the engine of such vehicles by taking it out and revving the piss out of it for the first time in its life and wondered why they blew the engine.

Rods and pistons need to be heated up and 'stretched' or a ridge on cylinder walls may develop. This microscopic ridge needs to be exceeded once in a while or the risk of blowing the engine increases over time. Of course, this phenomenon depends on the quality of the block somewhat. High nickel content blocks -- not so much. Soft blocks (like aluminum alloys) -- more so.

I run the car on highways for 20-30 minute increments of constant speeds (or RPMs) from, say 65MPH to 75MPH to 80MPH (and more) over a period of time until satisfied.
 
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2015 Forester 2.5i CVT Limited - TR580/FB25BC
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Discussion Starter · #8 · (Edited)
@Pugetpower
I am guessing a high mileage engine with valve stem seal wear.
58500. Bought it at 27500 in 2017.
You probably are down more than one quart at oil changes.
Oil was a little lower last time, not a quart. Changed it last time after 3500 miles and it was dark. I think I may have overfilled by ⅓ quart previously.
Mobile 1 Advanced Fuel Economy 0W-20
Wood Rectangle Ingredient Cuisine Dish

One thing is it seems my fuel mileage has dropped relative to a few years back.
 

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2011 Forester
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Hit the gas hard from a slow speed, about 10mph, and got up to about 5000 rpm and noticed a cloud of white smoke coming out of the tailpipe.
Is this an automatic transmission? Does this happen at the bottom of a hill? If so, this sounds like a crack in the diaphragm on a gadget mounted on the side of the transmission connected to a vacuum hose. Don't know if your Subie has such a gizmo, couldn't come up with the proper name for the thing to search. This stymied me for a long time on a Mazda Miata.
Crawl under and see if a vacuum hose comes off the transmission. Then take a picture of the gadget and get a replacement. I apologize if this is a waste of time, but the symptom perfectly matches.
 

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2015 Forester 2.5i CVT Limited - TR580/FB25BC
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Discussion Starter · #10 ·
Is this an automatic transmission? Does this happen at the bottom of a hill?
@KW England Yes, it's an automatic transmission - a CVT. It didn't happen at the bottom of a hill - on flat ground. I am taking it in for a compression test on Monday. Also want to have them inspect the transmission. I feel that it's exhibiting symptoms of going bad. It was quite warm out when this happened, 85 ºF, so not sure if could be related to cold or condensation.
 

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Discussion Starter · #11 ·
@08subfor
@johnnyjackhammer -- Ther IS a need to run hard once in a while, as @abc states. By babying the car, a disfavor towards the vehicle is being made.
I get it above highway speeds 70 - 85. I just rarely need to punch it so hard from a slow roll. 5000 rpm is hard when you are starting from a slow roll on city streets. A lot of weight to move all at once. I think it could be the head gasket.
 

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That was my initial thouhgt, upon reading the thread's title, too. It may be a small, maybe intermitant, HG leak for now. But if it is, the leak is internal, which means HG change.
I know next to nothing about Subaru CVTs.
Best wishes!
 
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johnnyjackhammer

White smoke is very seldom (ever?) oil related.
Most often, the "smoke" is water vapor condensing when it's cold.
Otherwise, it's typically coolant burn caused by a head gasket leak..
.
A head gasket leak can take several different forms:
  • Oil leak to outside of engine - You see the oil
  • Oil leak to into coolant - You see the milky foam in the oil
  • Coolant leak to outside of engine - You see the coolant (sometimes)
  • Coolant leak into combustion chamber(s) of engine - You see white smoke
It's the last one that causes "actual" white smoke, and it's possible to not have any of the other symptoms with a failing HG.
Depending on severity, it could take a considerable amount of time before you notice your coolant level dropping, as it doesn't take much coolant to make a lot of smoke.

I suggest you keep an eye on your coolant tank so you don't overheat the car, especially if the problem gets worse.
There have been some success stories with people using stop leak formulations that you might want to explore if the problem continues/gets worse.

Good luck.
 

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2019 Forester - Touring CVT
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Is this an automatic transmission? If so, this sounds like a crack in the diaphragm on a gadget mounted on the side of the transmission connected to a vacuum hose.
Your thinking of the Modulator. It used engine vacuum to measure engine load and adjust the internal transmission oil pressure to match the engine load. They were a common failure point on transmissions which used them (which was all US manufacturers except Chrysler). However, modulators were phased out with the advent of electronically controlled transmissions. No modern car has used a modulator since around 2000 or so.
 

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It has always been pretty obvious to me, but then maybe I have more experience..
;)
:) So about 30 years ago my son (in his teens at the time) had a dodge charger which he let get to the outside of a curve in sandy Florida and once the right wheels got into the sand, it rolled onto the roof. Stayed that way until the tow truck arrived and towed it to my house and put it into the garage. I looked it over and and figured it should start. Of course I didn't think about all the oil in the upside down engine running from the valve cover into the intake via the PCV valve. It started right up and several of my neighbors called the Fire Department. You never saw such a thick whiteish blue smoke bellowing out everywhere.
 

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Discussion Starter · #20 ·
Thanks everyone for the input.

The result from the dealership: two mechanics drove it and two looked at it. Checked the engine for any external leaks and did a compression check and "found nothing". Asked about the smoke and one said it could have been carbon burning off and they would advise, top engine cleaner, fuel injector cleaner, etc. The service writer kept saying, "Condensation inside the exhaust system". I can't understand how driving 40 minutes then parking in the sun, temps at 85 ºF, for 30 minutes during the midday would create condensation in the exhaust system.

Everyone agrees that only water can cause white smoke and that's what two people saw (wife as witness). Huge plume of white smoke the first time and barely any the second time 15 minutes later, then a week later tried again and there was none.

Maybe the color was "blueish white", and we couldn't tell the difference, why would the car be burning oil? There are no warning lights and they didn't pick anything up on their computer.

So stumped. But I am going to use two bottles of the Subaru Coolant Conditioner when I refill after flushing the system and get ahead of this. I will also do the top engine cleaning, the throttle body, the MAF sensor. I will proceed with the drain and flush of the transmission x2 as well. Going to send a sample of the oil and trans fluid to Blackstone.
 
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