CVT Cold Weather Issues

39520 Views 87 Replies 32 Participants Last post by Crosstrek2018, Feb 3, 2019

72fordgts

Discussion Starter · Dec 17, 2017

I recently left our '16 Outback parked outside all night when the temperature went down to about -10 F. I plugged the block heater in, and I warmed the car up for a few minutes prior to leaving. I noticed when driving the CVT refused to "upshift" once at higher speeds to drop the RPM's to it's normal crusing speed. It seemed to want to hover around 2000 RPM. I thought it was due to the low engine temperature, but this behaviour continued even after the car was fully warmed up to operating temperature.

If I went to manual mode I could shift it into "6" and it would stay at normal engine speeds, but otherwise it seemed to refuse to do so when in automatic mode.

Has anyone ever seen this before? Is this normal for these cars? Seems to me once the engine is warmed up it should go back to normal behaviour. Or is it because the ambient temeprature was so low when I was driving the car?

Any ideas?

Reactions: 1

1 - 20 of 88 Posts

ammcinnis

· #2 · Dec 17, 2017

72fordgts said:
Seems to me once the engine is warmed up it should go back to normal behaviour. Or is it because the ambient temeprature was so low when I was driving the car?

When it comes to transmission behavior, engine coolant temperature doesn't matter as much as CVT fluid temperature. Most likely, your CVT fluid never warmed up sufficiently at that very low ambient temperature ... especially if the trip duration was relatively short.

Models with the 2.5 engine have a dedicated heat exchanger that diverts engine coolant to warm the CVT fluid as well as cool it, but the 3.6 still relies on an old-style heat exchanger in the lower radiator header tank. To make matters worse, all Outbacks have a second CVT fluid cooler in front of the radiator. In my experience (2015 Legacy 2.5, 2016 Outback 2.5), CVT fluid temperature rise lags 40 degrees (F) or more behind engine coolant temperature following a cold-weather start.

Danver

· #3 · Dec 17, 2017

Most likely normal. It will behave that way until the transmission temperature gets up to around 160 degrees I believe. The engine being up to normal temp doesn't mean the transmission has.

It was -9F here yesterday morning and I was about 6 miles from home before rpms dropped to normal and that was also after warming the car up for about 5 minutes before leaving.

Fibber2

· #4 · Dec 17, 2017

This has been an issue that I've mentioned before on the Gen-IV forum as well. My 2014 with the 2.5L FB engine and TR-580 cvt (pretty much what's in the Gen-V wagons) begins this behavior at around 40'F. The colder it is, the longer it takes to allow 'upshifts to 6th' even at road speeds beyond 50 mph. It will run about 500 RPM higher than expected, and stay that way even 5 miles from home (approximately 6+ minutes on country roads) on single digit days.

At least with the manual temperature controls on my 2.5 Premium there are two 'defeats' to this feature that work reliably after about 1.5 miles (when the blue 'cold' light goes off).

1) Turn the fan speed to "off". Within seconds, RPM will drop to normal.
2) Dial the manual temperature setting off the max heat position by two clicks. Below 10' F it might take 3 clicks to get it going, and then I can go back to 2 clicks off max.

I realize that the 2015 and up climate control is different, but I'll bet there is still some level of interaction present. Try playing around and see if you can influence engine calibrations.

See less See more

mikelipke

· #5 · Dec 17, 2017

It is not an issue, it is normal. I have a six speed Sienna that does the same thing, as did my '13 OB, my '11 Ford Flex, my '09 Jeep, etc.

Danver

· #6 · Dec 17, 2017

Fibber2 said:
This has been an issue that I've mentioned before on the Gen-IV forum as well. My 2014 with the 2.5L FB engine and TR-580 cvt (pretty much what's in the Gen-V wagons) begins this behavior at around 40'F. The colder it is, the longer it takes to allow 'upshifts to 6th' even at road speeds beyond 50 mph. It will run about 500 RPM higher than expected, and stay that way even 5 miles from home (approximately 6+ minutes on country roads) on single digit days.

At least with the manual temperature controls on my 2.5 Premium there are two 'defeats' to this feature that work reliably after about 1.5 miles (when the blue 'cold' light goes off).

1) Turn the fan speed to "off". Within seconds, RPM will drop to normal.
2) Dial the manual temperature setting off the max heat position by two clicks. Below 10' F it might take 3 clicks to get it going, and then I can go back to 2 clicks off max.

I realize that the 2015 and up climate control is different, but I'll bet there is still some level of interaction present. Try playing around and see if you can influence engine calibrations.

Interesting. I will have to play around a little and see if that has any effect in my '17. In automatic mode it doesn't because that is yet another thing that bugs me. The blower stays on a very low setting until the engine temp comes up quite a bit. I want that blower going right away. Even a small amount of warmer air is going to start melting ice and snow off of the glass long before the blower kicks on in auto mode. And in auto mode with the blower almost off the "shifting" is delayed until everything gets up to normal operating temps.

But maybe with the heater controls in manual mode there will be some interaction.

mikelipke

· #7 · Dec 17, 2017

You don't have to go to manual mode. Just press the fan speed button to raise the fan speed. It over rides the Auto mode.

ammcinnis

· #8 · Dec 17, 2017

Just be aware that increasing fan speed may (or may not) indeed divert more heat to the cabin, but at the expense of slower CVT warming. Slow warm-up is one undesirable side effect of modern, high-efficiency engine designs: there is simply less waste heat available.

Danver

· #9 · Dec 17, 2017

mikelipke said:
You don't have to go to manual mode. Just press the fan speed button to raise the fan speed. It over rides the Auto mode.

That's right. I didn't think of that when I was posting but I always turn the blower speed up before I take off so I guess it doesn't make a difference with the rpms on mine because they still stay high for quite a while.

Danver

· #10 · Dec 18, 2017

ammcinnis said:
Just be aware that increasing fan speed may (or may not) indeed divert more heat to the cabin, but at the expense of slower CVT warming. Slow warm-up is one undesirable side effect of modern, high-efficiency engine designs: there is simply less waste heat available.

My first thought with this was that the fan speed might have an effect on engine warmup but shouldn't make any difference with the CVT temperature. But after reading your earlier post about the heat exchanger with the 2.5 there absolutely could be a connection there. Whether the effect would be significant or not I have no idea. Interesting to contemplate though. I might have to do some experimenting with that as well.

Amazing the things that can be learned here.

AbsoluteZero

· #11 · Dec 18, 2017

I suspect higher engine speed in cold weather is a mechanism to bring the catalytic converter up to temperature quicker.

Reactions: 1

72fordgts

Discussion Starter · #12 · Dec 19, 2017

Interesting infromation, thank you. It was warmer this morning and I kept the fan speed lower, and it drove like it normally does. This car is very cold blooded, and the other day I did drive it for about 20 miles round trip. Mind you I was in an out of the car, but even at the end of the trip it still wasn't "shifting into high gear." It almost seems like these cars could use a winter front.

My Toyota truck won't lock-up the torque converter until the truck is warmed up a bit. But on my truck the engine is usually half-way wamred up and the trans wil shift normally. It is very short in comparision to the Outback, and I always thought my truck was cold blooded (until I got this Subaru that is). My truck also has a HD tow package but the transmission cooler is thermostatically controlled. I also have a trans temperature gauge, and it operates normally well before it's at operating temperature, even in -40 weather.

Danver

· #13 · Dec 19, 2017

I didn't notice any difference this morning no matter where I set the fan speed. The rpms stayed up around 2000 for around the same distance on the way to work. It would be interesting to be able to monitor the transmission temperature while driving. I can bring transmission temp up on the dash of my GMC truck which is nice when I am towing.

My OBDII scanner has live data but I'm not sure if transmission temp is included or if it will work on the Subaru for that matter. I loaned it to a coworker a couple of weeks ago so I will have to get it back and try it.

dat2109

· #14 · Dec 19, 2017

Some scanners will be able to display transmission fluid temp.

I find the GEN5 outback to warm up slower than I was expecting - but not too slow or anything, it is still very reasonable.

phaem

· #15 · Dec 19, 2017

2016 Limited 2.5: I find that at 50 F or above the transmission behaves normally. Between 32 F and 50 F the transmission behaves normally if i turn off climate control. Below 32 F the transmission behavior is not responsive to climate control initially, but within a few minutes it returns to normal transmission operation (the colder it is the longer it takes) if climate control is off. Once operation resumes normal, turning climate control on results in a return to higher revs unless the engine has reached near normal coolant temperature. In sedate driving, engaging the climate control actually reduces engine coolant temperature.

I formulate the theory that transmission programming depends upon key-on ambient temperature, transmission temperature, and call for cabin heat in relation to engine coolant temperature. Only below freezing does it appear that the program seeks to warm up the transmission itself. At 32 F to 50 F, or after the transmission reaches an appropriate temperature, revs are held higher (it would seem) only to improve cabin heat.

See less See more

DNMakinson

· #16 · Dec 19, 2017

I think this question will fit here, rather than starting a new thread.

New 2018 Outback 2.5. At 30F ambient, this car takes 20 minutes to warm up fully (much longer for engine oil temp to stabilize).

I know that my Expedition takes a long time like that, but other cars I have had, Camry, Miata; warm up in less than half that time.

For the Subaru, is this normal, or should I have the dealer look into it?

ammcinnis

· #17 · Dec 19, 2017

phaem said:
I formulate the theory that transmission programming depends upon key-on ambient temperature, transmission temperature, and call for cabin heat in relation to engine coolant temperature. Only below freezing does it appear that the program seeks to warm up the transmission itself.

In the 2.5 there is a dedicated coolant loop to the CVT heat exchanger, regulated by its own thermostat. According to Subaru documentation, that thermostat begins to open at ~120 F and is fully open at ~140 F. From my own observations using an OBD-II scan tool, ~140 F is also the point at which the automatic climate control system begins to ramp up fan speed (assuming cabin heat is requested).

On a cold day it's not unusual for coolant temperature to plateau between 140 and 150 F for several minutes as the engine warms up during initial driving, reflecting that the CVT and climate control system are absorbing heat from the coolant almost as fast as the engine is producing it. The CVT typically seems to absorb a lot of heat following a cold start.

For completeness, an unlocked torque converter is also a significant source of heat input to the CVT fluid. Normally undesirable, this mechanical heating is actually helpful following a cold start, and the CVT controller may be programmed to take advantage of it by leaving the TC unlocked longer than usual.

See less See more

dakotarayne

· #18 · Dec 19, 2017

I've noticed the same behavior with my 17 2.5. I have a scangauge plugged in with the CVT temp displayed. I notice the higher RPMs until the CVT fluid is around 100 degrees F. Then it calms down.

Rub

· #19 · Dec 19, 2017

ammcinnis said:
In the 2.5 there is a dedicated coolant loop to the CVT heat exchanger, regulated by its own thermostat. According to Subaru documentation, that thermostat begins to open at ~120 F and is fully open at ~140 F. From my own observations using an OBD-II scan tool, ~140 F is also the point at which the automatic climate control system begins to ramp up fan speed (assuming cabin heat is requested).

On a cold day it's not unusual for coolant temperature to plateau between 140 and 150 F for several minutes as the engine warms up during initial driving, reflecting that the CVT and climate control system are absorbing heat from the coolant almost as fast as the engine is producing it. The CVT typically seems to absorb a lot of heat following a cold start.

For completeness, an unlocked torque converter is also a significant source of heat input to the CVT fluid. Normally undesirable, this mechanical heating is actually helpful following a cold start, and the CVT controller may be programmed to take advantage of it by leaving the TC unlocked longer than usual.

You say that in such a sexy way. I almost imagine your computer has a soft, smokey voice.

ammcinnis

· #20 · Dec 19, 2017

Rub said:
I almost imagine your computer has a soft, smokey voice.

I suggest that you pair it with a modest Pinot Noir.

1 - 20 of 88 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.