CVT temps in hot weather

[D1dad]

If your belt is slipping, which it sounds like it is. I’d service it , today and start shopping new and or used cvts. The only failure I ever had was on an 09 under extended warranty that started whining. The dealer thought a service would fix it but I pushed for the transmission. I never changed cvt fluid, didn’t know. It went out at 95k. That replacement transmission is as good as new at 75k, but I also learned and replaced fluid every 10-20k. Heat kills the fluid and Nissan never tells you that, why I have no idea.

[Krishna_AbKing]

I have to revive this thread because I have a Blue Light Special in the Live-and-Learn department. Some of you may have noticed I just installed a CVT temperature gauge on the wife's '13, mainly because I got tired of using my phone for an instrument panel. That CVT has always run 160~170F in hot weather, 140~150F's in the winter. We've had the car for 70K and it gets new fluid every 20~25K, and it's always run at those temps. Not that 170F is harmful, but I kept noticing that D1dad's Altie and a lot of other forum folks generally saw temps 20F or so cooler than that. My customers who watch their temps generally ran a bit cooler too. I wondered why, so along with installing the gauge, I started poking around looking for a reason. Lo and behold, I discovered that the embedded thermostat that's supposed to shut off coolant to the beehive was stuck wide open, not just a bleed-flow when warm like it's supposed to. So it was dumping hot coolant into the beehive all the time, not just when the transmission needed warming. It's probably been that way since we bought the car. I changed it out and presto, 140F on flat highway instead of 160F, 150F in the hills instead of 170F.

That's like -- c'mon, man. That 'stat is something nobody ever thinks about. Lots of techs don't even know it's there.
Now I'm wondering how many cases of "repeated failure" might owe something to that butt-stupid little valve.

Reviving this old thread.. there is definitely a wealth if info here, shared by VStar650.

I have had my 2014 2.5L since new, and I have replaced CVT fluid thrice in 80k miles. I have Hayden bypass cooler installed in-line with the radiator oil cooler, which activates at 180F, so its not used most of the time. I have noticed that CVT runs at 125-130F on highway drive, when its 30F outside. It runs at 150-165F on same highway drive, when its 65-80F outside. So there is a direct correlation of CVT temperature to outside air temperature. Engine coolant is always between 180-195F.

I live in Boston, in winters CVT takes good 15-20 miles highway drive to even get to 125F; in short trips lets say city drive of 5-6 miles, it barely reaches 80-100F.

I have noticed that if I sit in traffic, the CVT temperature starts climbing quickly, even in winter. In a recent trip, I was on highway with CVT at 130F, after that I sat in traffic for 20 mins, CVT temperature gradually climbed from 130F to 185F. My gut feel is engine coolant is dumping heat in the CVT fluid.

I believe there are two point where engine coolant sends heat to CVT (1) Beehive (2) Radiator bottom tank. Beehive thermostat may be closed (so no hot coolant going to Beehive), but Radiator bottom tank is still heating up the CVT fluid, when Radiator is cooling the coolant. The Radiator bottom tank is around 180F, and that's always heating up CVT fluid.

As per my understating, Nissan has designed the system to keep CVT fluid around 180F (Radiator bottom tank temperature).

Let me know if I am thinking right.. some of you senior guys like VStar650CL, definitely know a lot.

[VStar650CL]

The outlet tank, which is where the heat exchanger is located, will run a lot less than 180F unless the cooling system is very stressed. The radiator's job is to dump heat, and the coolant in the outlet tank has already passed through the fins. I've also discovered that the CVT thermostats operate like a normal 'stat, which is opposite what I was originally told and seems completely nonsensical. In essence, Nissan is heating up the fluid endlessly with no thermal limitations or controls, then relying on the exchanger to counteract the excess before it gets back to the transmission. To me, that's a Blue Light Special in the "I Don't Get It" Department.

Anyway, in real life, your 180F cooler isn't doing you much good. It will drop the temperature when it cracks, but the 185~190F that results is already above optimal, which is in the mid 170's. The trouble is, the fluid in the pan and hive has thermal mass that the cooler needs to overcome after cracking, so the steady-state temperature will always be above crack temperature and it will always go too high before it levels out. I've switched to a Hayden 697 on the wife's Altie and it's much better, with a crack temperature of around 160F. That also works better with my self-designed CVTsaver, which replaces the thermostat with a temperature-controlled poppet valve that kills flow to the hive above the 170F's. For the cooler, another very good alternative is to swipe one from an R52 Pathfinder in the junkyard, those crack in the 140F's because they're specifically intended for towing.

[Krishna_AbKing]

The outlet tank, which is where the heat exchanger is located, will run a lot less than 180F unless the cooling system is very stressed. The radiator's job is to dump heat, and the coolant in the outlet tank has already passed through the fins. I've also discovered that the CVT thermostats operate like a normal 'stat, which is opposite what I was originally told and seems completely nonsensical. In essence, Nissan is heating up the fluid endlessly with no thermal limitations or controls, then relying on the exchanger to counteract the excess before it gets back to the transmission. To me, that's a Blue Light Special in the "I Don't Get It" Department.

Anyway, in real life, your 180F cooler isn't doing you much good. It will drop the temperature when it cracks, but the 185~190F that results is already above optimal, which is in the mid 170's. The trouble is, the fluid in the pan and hive has thermal mass that the cooler needs to overcome after cracking, so the steady-state temperature will always be above crack temperature and it will always go too high before it levels out. I've switched to a Hayden 697 on the wife's Altie and it's much better, with a crack temperature of around 160F. That also works better with my self-designed CVTsaver, which replaces the thermostat with a temperature-controlled poppet valve that kills flow to the hive above the 170F's. For the cooler, another very good alternative is to swipe one from an R52 Pathfinder in the junkyard, those crack in the 140F's because they're specifically intended for towing.

I have Hayden 696 installed, I thought it opens at 180F, good to know its 160F.

Another observation, I have babied the car since beginning, installed cooler and did fluid change with Nissan NS3.. simply because, soon after buying it new, I realized the CVT was not very robust. But despite all that the CVT had developed noticeable vibration and noise. So, I intentionally switched to Valvoline CVT fluid (its NS-3 compatible), as its a little thicker fluid (higher viscosity).. and that did take care of a lot of noise/vibration. Now CVT is much smoother.
I know, its strongly suggested to stick to Nissan NS3, but in my experience, that fluid is too thin (low viscosity) to protect the CVT properly, and is probably one of the cause behind a lot of CVT failures.

[VStar650CL]

Yah, I contacted Hayden and they told me the 69x's all open at 160F. There wasn't anything in the literature, so I took their word for it. The one in the wife's car was new last fall, the hot weather will tell if they were lying to me.

NS3 is a good fluid but very noisy. It's formulated for gas mileage and not quietude. Valvoline is actually pretty noisy too. If you really want quiet, try Eneos or AMSoil.

[Krishna_AbKing]

Yah, I contacted Hayden and they told me the 69x's all open at 160F. There wasn't anything in the literature, so I took their word for it. The one in the wife's car was new last fall, the hot weather will tell if they were lying to me.

NS3 is a good fluid but very noisy. It's formulated for gas mileage and not quietude. Valvoline is actually pretty noisy too. If you really want quiet, try Eneos or AMSoil.

surely, next time AMSoil.. its also a thicker fluid, so should help with vibration/judder.
In my opinion, as the vehicle age.. with wear and tear the clearances/gaps between various moving parts increase.. so higher viscosity fluids typically do a better job of protecting, be it engine or transmission, I recently switched to 5w30 in engine from 0w20, which I have always used in past (ofcourse at the cost of mpg).

[VStar650CL]

Don't go thicker than 5W, you'll start getting P0011's in cold weather. AMSoil isn't really much thicker, it actually has a much lower cold pour point than most of the competition and I recommend it to anybody who lives in the snow belt. CVT's are just glorified friction-drives, and all CVT fluids need to be compromises between allowing belt traction and keeping metal off metal. Those ends are obviously somewhat opposed, so the fluids have some very special properties to walk the knife edge of that compromise. Some do it better than others.

[Krishna_AbKing]

Don't go thicker than 5W, you'll start getting P0011's in cold weather. AMSoil isn't really much thicker, it actually has a much lower cold pour point than most of the competition and I recommend it to anybody who lives in the snow belt. CVT's are just glorified friction-drives, and all CVT fluids need to be compromises between allowing belt traction and keeping metal off metal. Those ends are obviously somewhat opposed, so the fluids have some very special properties to walk the knife edge of that compromise. Some do it better than others.

Thanks for the advice!
one more observation, I have noticed that when CVT is at 180-190F (which is not very frequently), there is CVT fluid smell, I can smell it inside and outside, near the hood. I noticed this after changing over to Valvoline (last 3-4k miles), never before. Any idea what's going on ?

[VStar650CL]

There's a J-shaped vent hose on the CVT which comes up on the righthand side of the airbox.

[Krishna_AbKing]

There's a J-shaped vent hose on the CVT which comes up on the righthand side of the airbox.

What do I need to do with the vent hose ?

[VStar650CL]

Nothing, but the smell is probably coming from there. The fresh air intake is about 18" away from it under the cowl, so any smell coming out of the vent would undoubtedly make it inside the cabin. If you didn't DIY the last fluid change, make sure they didn't overfill it.

[Krishna_AbKing]

Nothing, but the smell is probably coming from there. The fresh air intake is about 18" away from it under the cowl, so any smell coming out of the vent would undoubtedly make it inside the cabin. If you didn't DIY the last fluid change, make sure they didn't overfill it.

Thanks much!

Can I ask your opinion on a totally off-topic thing.. since you are a tech. Couldn't find a way to send you an IM, so posting here.
Any thoughts/experience with Acura MDX (its a Honda Pilot clone) ? I am looking for getting 2020 MDX.

[VStar650CL]

Nope, sorry. I'm strictly a Nissan guy and they don't make me do used car UVI's anymore.

[D1dad]

I’m at 79k on the wife’s rogue, just drove 600 miles round trip to northern kentucky and back. I serviced the cvt with 5qts of Lubegaurd complete prior and saw higher than normalish cvt temps. Generally 180-200 in hot weather and hammering down through the hills. The occasional 215 reaching the top of a mountain. This time I averaged around 200 the whole time. I still have 6k left on the extended warranty, but will for sure add an extra cooler after. The trans has never sounded better that with Lubegaurd, but the cvt did run a few degrees hotter with the fluid for some reason.

[Krishna_AbKing]

The outlet tank, which is where the heat exchanger is located, will run a lot less than 180F unless the cooling system is very stressed. The radiator's job is to dump heat, and the coolant in the outlet tank has already passed through the fins. I've also discovered that the CVT thermostats operate like a normal 'stat, which is opposite what I was originally told and seems completely nonsensical. In essence, Nissan is heating up the fluid endlessly with no thermal limitations or controls, then relying on the exchanger to counteract the excess before it gets back to the transmission. To me, that's a Blue Light Special in the "I Don't Get It" Department.

Anyway, in real life, your 180F cooler isn't doing you much good. It will drop the temperature when it cracks, but the 185~190F that results is already above optimal, which is in the mid 170's. The trouble is, the fluid in the pan and hive has thermal mass that the cooler needs to overcome after cracking, so the steady-state temperature will always be above crack temperature and it will always go too high before it levels out. I've switched to a Hayden 697 on the wife's Altie and it's much better, with a crack temperature of around 160F. That also works better with my self-designed CVTsaver, which replaces the thermostat with a temperature-controlled poppet valve that kills flow to the hive above the 170F's. For the cooler, another very good alternative is to swipe one from an R52 Pathfinder in the junkyard, those crack in the 140F's because they're specifically intended for towing.

I have Hayden 696 installed, I thought it opens at 180F, good to know its 160F.

Another observation, I have babied the car since beginning, installed cooler and did fluid change with Nissan NS3.. simply because, soon after buying it new, I realized the CVT was not very robust. But despite all that the CVT had developed noticeable vibration and noise. So, I intentionally switched to Valvoline CVT fluid (its NS-3 compatible), as its a little thicker fluid (higher viscosity).. and that did take care of a lot of noise/vibration. Now CVT is much smoother.
I know, its strongly suggested to stick to Nissan NS3, but in my experience, that fluid is too thin (low viscosity) to protect the CVT properly, and is probably one of the cause behind a lot of CVT failures.

I keep coming to this thread, as I see a lot of valuable insights in this thread.

I live in Boston (cold winters), and did 2 CVT Oil changes on 2014 Altima (2.5) last year. After that CVT is much smoother, and judder is significantly reduced.
But I noticed that in winters (cold Boston winters), CVT never goes above 100F in city driving, and 125-130F in highway driving. And at those temperatures, there is some judder.

At this time of year (80F in Boston), there is no judder at all. CVT starts warm, and maintains 150-165F. I have Hayden (thermal bypass) transmission cooler installed on the car.

That makes me think that some judder I am experiencing is because of colder winter temperatures.

I am thinking of insulating the CVT oil pan, so that CVT can run little warmer in winter. Is this a good idea ?
if yes, what kind of material can I use to insulate it ? any suggestion

[VStar650CL]

Below 100F is definitely too cold. Before insulating anything, make sure your cooler's bypass isn't leaking and make sure you're running 50-50 coolant and not straight antifreeze. You can see if the cooler is causing the issue by pinching it off in cold weather and seeing if your temps rise. There's also a thermostat on the inlet line to the beehive, if that's stuck shut it will definitely cause cold running in cold weather.

[Krishna_AbKing]

Thanks VStar650CL!
Car is running 50:50 coolant, I replaced coolant myself last year, and there is no air in the system, as Engine is running normal temperature (180-190F).

Would you mean, pinching the pipe to the Hayden cooler (additional cooler, which I installed)?
My Hayden cooler is installed in series with the Radiator cooler, so after I pinch the hose, it would also stop the fluid flow through the radiator cooler.

BIG question is - Can it cause any problem by reducing fluid flow in the CVT ?

BTW last winter, I put a sheet of plastic in front of Hayden cooler, exactly touching the cooler, to avoid air passing through it, but that didn't make any difference to fluid temp.

[D1dad]

I swapped out the rogue cvt with 8qts of eneos eco. Trans temps are back down in the 180 range. Lubeguard was thicker thus causing higher heat. I just ran to the lake in Michigan back, 6 hrs round trip in 90 degree heat and averaged 185 at 85 mph which is fine. I have the cooler, just haven’t gotten off my lazy azz and installed it. The biggest issue without a cooler is the heat breaks down the fluid and no service equals a crapped out cvt. My 09 made it to 95k unserviced before it started whining. The replacement cvt gets serviced annually and is approaching 100k and no signs of giving up. And that was a bad period for jatco.

[Krishna_AbKing]

Thanks VStar650CL!
Car is running 50:50 coolant, I replaced coolant myself last year, and there is no air in the system, as Engine is running normal temperature (180-190F).

Would you mean, pinching the pipe to the Hayden cooler (additional cooler, which I installed)?
My Hayden cooler is installed in series with the Radiator cooler, so after I pinch the hose, it would also stop the fluid flow through the radiator cooler.

BIG question is - Can it cause any problem by reducing fluid flow in the CVT ?

BTW last winter, I put a sheet of plastic in front of Hayden cooler, exactly touching the cooler, to avoid air passing through it, but that didn't make any difference to fluid temp.

Any thoughts on above.. any experts ?

[VStar650CL]

Would you mean, pinching the pipe to the Hayden cooler (additional cooler, which I installed)?
My Hayden cooler is installed in series with the Radiator cooler, so after I pinch the hose, it would also stop the fluid flow through the radiator cooler.

Yah, sorry, on a '14 it would be. Pinching it won't tell, you'd need to temporarily splice out the cooler so the radiator was still in the loop. Doable, but it's a lot more work and mess than a clamp. The next best thing is to do touch-and-feel on the cooler. If the bypass is sealed then you should only feel heat near the hose fittings when the transmission fluid is below crack temperature, the fins should be cool or lukewarm. If the fins are getting hot like the hoses then the bypass is leaking.

[Krishna_AbKing]

Would you mean, pinching the pipe to the Hayden cooler (additional cooler, which I installed)?
My Hayden cooler is installed in series with the Radiator cooler, so after I pinch the hose, it would also stop the fluid flow through the radiator cooler.

Yah, sorry, on a '14 it would be. Pinching it won't tell, you'd need to temporarily splice out the cooler so the radiator was still in the loop. Doable, but it's a lot more work and mess than a clamp. The next best thing is to do touch-and-feel on the cooler. If the bypass is sealed then you should only feel heat near the hose fittings when the transmission fluid is below crack temperature, the fins should be cool or lukewarm. If the fins are getting hot like the hoses then the bypass is leaking.

Thanks VStar650CL! always appreciate your inputs.

Thinking out loud, will try blocking off the Hayden CVT cooler with a piece of Foam in winter.. that will make sure that cooler is not cooling, regardless of bypass leak or not. Sorry, just looking for least amount of work. Last time I blocked it with a plastic sheet, that didn't help, probably foam would work better.
If that still didn't work, probably the next option would be to insulate the CVT pan with foam.

[VStar650CL]

Going back to my original suggestion, check the beehive thermostat too. The coolant line into the beehive comes straight from the cylinder head, on the same loop as the heater core. After running awhile it should be too hot to touch comfortably on both sides of the 'stat. If the side toward the beehive is cooler than the side toward the engine, then the 'stat is stuck shut.

[Krishna_AbKing]

great, thanks!

[Krishna_AbKing]

I recorded the CVT and Coolant temperature this morning. This data is from a easy 6 miles suburban drive, over 12 mins. When I pulled the car out of garage CVT temp was 78F, and over 12 mins of drive it slowly rose to from 78F to 115F.

The engine reached full operating temperature in 5 mins of drive, but you can see that it didn't make any immediate difference to the CVT temperature. The CVT temperature continued to rise slowly. I would have expected that once engine reached the operating temperature, the hot coolant would help CVT warm up quicker.

This is in 70F outside temperature. In winters with 20-30F temperatures, CVT temp rise is even slower.. in Winter, in the same 6 miles drive.. the temp by the end of drive doesn't even reach 100F.

Does this data/chart help diagnose? VStar650CL any thoughts ?

Questions:
1. At what coolant temperature does the coolant line thermostat OPEN to start warming up the CVT fluid ?
2. At what coolant temperature does the coolant line thermostat CLOSE to stop warming up the CVT fluid ?
3. Is there a similar thermostat on the CVT fluid line going to lower radiator tank for cooling ? or is the CVT fluid always cooling through radiator ?

Any inputs would be very valuable.

[VStar650CL]

The 'stat should crack at 160F and be wide open at 203F. It's also possible there's a blockage in the fluid lines and not the coolant lines. The prime culprit for that is the heat exchanger. The fluid orifices in the exchanger are smaller than a millimeter, so it doesn't take much debris to clog it up. The paper filter is supposed to catch that stuff, but I've seen plenty of instances where shavings ended up in the exchanger anyway. It might pay you to jack the car up warm and do some touchy-feely on the fluid outlet hose. The one toward the driver's side of the beehive is the outlet and should be about the same temperature as the beehive. If it isn't, something is blocked on the fluid side of the plumbing.

[Krishna_AbKing]

will try to check.. thanks!

[VStar650CL]

FYI for those interested, this is a cutaway from a typical CVT heat exchanger which I dissected to see what was in there. The tiny passages are the reason they always need to be back-flushed to clean them out. Flushing forward accomplishes little or nothing, because you can't force much through those miniscule tubes.

Heat Exchanger Cutaway.jpg (64.15 KiB) Viewed 2603 times

[Krishna_AbKing]

Returning to this thread, here is the summary:
I have 2014 Altima 2.5, with 88k miles. Have had the car since New, and have always babied it. The CVT fluid has been changed 4 times, and 3 changes only in last 12k miles.
I don't drive this car much, 5-6k miles a year.

The CVT is much smoother after the fluid changes.

The CVT drives silky smooth in Warm weather (Temp's above 65 F).
At this time of year, as its getting cold (I am in Boston, dropping to 20-30's), I feel the judder at low RPM's, typically between 1000-1500k. When its vibrating, if I push little harder on the gas pedal, or let it go little bit, the vibration goes away. The vibration is almost of the engine lugging, especially in manual/gear cars. I believe its coming from the Torque converter.

Wife has heavier foot, when she drives, it feels less the juddery. Also, if I put the CVT in Sport mode, Judder reduces.

The car had had this judder for few years now, and it has progressively gotten worse. But with recent fluid changes, it has reduced.

Few questions:
(1) what's causing the cold weather judder ? Is there an easy way to fix for it ?
(2) should I be worried ? I don't drive this car much 5-6k miles a year, and simply need this car to be there for local drives. If CVT failed, the car would go to junk yard; so, if this is a serious issue, would rather get rid of the car.

This car has been super reliable all this time, only thing that has ever gone bad is the front spring broke (rust by snow/salt), so had to replace front strut assemblies.

[VStar650CL]

The vibration you're feeling isn't judder, it's the Torque Converter staying locked (a gas-saving measure) and causing the engine to lug at light throttle. We got lots of inquiries about it when the gen5's first came out, to the extent that it got a nickname: The Old Lady Noise. Nissans pretty much all lug that way when you baby the gas, but the design of the exhaust and rear body in the gen5's turns it into "panel drumming" which many people find annoying. Thick fluid when cold exacerbates it a bit. Unfortunately there's no fix for it besides hitting the gas a little harder to unlock the TC, but the good news is, it isn't judder and it's quite harmless.

[VStar650CL]

PS - There's a possible issue with the front exhaust hanger on the '13~'15's which can very much exacerbate the noise. Easily fixed, see this bulletin:
https://static.nhtsa.gov/odi/tsbs/2016/ ... 7-2280.pdf