[Jaxxa]

Mine will eventually always get hotter than engine temp. From what I've read in other threads it seems like this is pretty common, of course not everyone can check their CVT temp on demand, so whether or not some people's CVT's stay cool or other people's CVT's roast themselves is hard to say. It makes me wonder how many people could have prevented destroying their transmissions if Nissan would have just put a CVT temp gauge in the dash, I certainly drive my Juke differently because of it.

 

[JukeyJukeJuke]

here's fast religeon's comments. I am not convinced about some of it, in other words I think I could implemenet a cvt pump and cooler and not have the issues he says it might have. could use a manual switch, bleed in the thermostat, etc. only thing stopping me is the money and the miles on our juke. but, the cvt asof now is working perfectly fine at 150k, despite the doomsayers ! and, maybe add a cooler pump just for the learning.

I was trying to make a product to sell, and thermostatic by-passes ad a LOT to the cost of the system and complexity. Not everyone knows how to tell of one is working right or not. So It had to be simple. You also have to deal with air at that point too. When you shut off a CVT the fluid will drain out the hoses and back into the CVT if the cooler is mounted above the adapter. This is fine when you just start the car back up, as the CVT self bleeds in a few seconds, and your not driving at that point. Now, if your driving the car and the thermostat opens to allow CVT fluid into the cooler, the CVT now has to burp that air in the cooler while it is already moving, which could cause aeration to occur in the fluid, making it more likely the CVT pickup will get bubbles in it and cause issues. Also: Shocking the CVT with ambient air temp fluid on the initial opening of that thermostat is bad too, the internal temp sensor for the CVT could see a dramatic drop in CVT fluid for a second and trip a code or limp mode, thinking something is wrong. You want it all to heat up and level off organically. There is a reason almost no affordable OEM's use thermostatic systems in regards to oil or hydraulics, too many potential issues. You jsut have to size the cooler to maintain a set temp in set circumstances.

At 150miles on the oem cvt, that CVT is just about done. Your lucky it has lasted that long. Highway driving is what kills a CVT. its a long duration of continued torque. Thats why most people get CVT limp mode on the highway, and not some back road. The CVT makes the most heat on the highway.

On the Insane juke I ran a self-priming pump designed for oil with a thermostatic switch with two lines directly into the modified CVT pan. IT was both overkill, and never did what it was meant to do as mentioned above. Your adding a lot of complications with a system like that.

All my jukes, my current one included, just use the OEM 4 barb beehive system. Ive sold hundreds of them, installed dozens of them, and never had any issues.

 

[Jaxxa]

He was a nissan technician for a long time and has worked on a lot of people's Jukes specifically, but the way he explains it sounds like he was trying to cool the fluid down to ambient temp, which of course if you are trying to cool CVT fluid down to like 60 or 70 degrees it's gonna be a huge problem. All you need is a reliable way to cool it about 30 degrees maximum, and a thermostat can handle the duty cycle to keep it from overcooling the fluid. As far as evenly distributing the cooled fluid, I think introducing it into a spot where it is closer to the primary pulley should probably be best (but of course low enough to be always full of fluid and not take on air), since it's the spinning action that pumps fluid into the beehive cooler (from what I've heard) makes sense to me since both of those things are toward the front. I read through this thread a while ago but I've been doing a lot of my own research into how CVT's operate, so I know a lot more now than I did 6 months ago.

One problem I just realized that he probably ran into but didn't mention, He opted to have the pump not full of fluid when the CVT is not operating, which he said caused aeration. But even if we keep fluid in the system the whole time, when the pump is off, that fluid will continue to cool and not circulate through the transmission, so instead of stopping the pump completely when not in demand, it has to be ran at a lower rate so it can still idle fluid through.

I am kind of interested, but really don't want to go tapping holes into the oil pan of a vehicle I daily drive. There are some less invasive options I want to try out first, personally

 

[pboglio]

Well, here is how the stock CVT cooling system works. Oil is picked up from the sump by the oil pump. Then it's fed into the valvebody so it can split the flow to hydraulics (clutches, pulleys, etc.) then another low pressure circuit is used for lubrication & cooling, about 75 psi or so. This then hits the oil filter/cooler, then hits the CVT belt injector and roller bearings. That then falls into the oil pump and it starts all over again. IF you run an external pump and cooler, you are simply running a parallel circuit that is ONLY dedicated to cooling. There is ZERO lubrication in that circuit because it's not tied into it. This works because the oil pump can now draw from the cooled sump oil which will help it out if all other things are equal.

Follow me on this guys, OIL FLOW is what keeps the CVT alive. When you replace the clogged oil filter on a CVT......it doesn't tend to overheat because you have increased oil volume to extract the heat. I did that and AMSOIL and I could not get it to hit limp mode when previously it would do it almost every time without mercy. I'll preface that it was mainly the wrong oil fluid LEVEL that caused overheating and cavitation, but the higher oil flow definitely helped even better with oil cooling. When the CVT wears out, then it overheats no matter what you do. I'm not saying this will solve all problems, but how many guys have their oil filter in perfect condition & their CVT fluid levels perfect? I guarantee this isn't a common condition so you have to be meticulous about that and the CVT oil level has to be bang on.

Hopefully that's clear, just because you slap an external pump on does NOT mean you increased oil flow to the things generating heat. If I did that and drastically cut the lubrication circuit flow for the lubrication circuit, the entire CVT would die very quickly even with an external oil pump and big cooler. The CVT oil pump has to push large volumes of oil flow in the lube/cooling circuit just to keep the belt and bearings alive, cooler is better but oil volume matters too.

Here's another one: Too cold and the oil pump starves and cavitates because the oil is too thick to pump.....very bad. Too HOT and the oil level rises due to thermal expansion and the belt whip aerates the sump oil.......and cavitates the pump, and you lose belt pressure. This is why when you nail the oil sump levels perfectly........magically the CVT stops overheating and whining. I live in Chicago so maybe the western states things are different.

It's possible a slug of air in an external oil cooler that dumps oil directly under the oil pump pickup might aerate the oil. I think it's B.S. but I haven't tried it. The CVT belt itself is churning the oil like mad and normally this is OK as long as the oil level is bang on perfect. This is the primary reason the oil pump cavitates but thick oil can do it without any air in the oil sump, so can a stuck oil pump flow relief valve which is it's main job to control pump cavitation. This is my point, there are many things in the CVT that can fail over time that will overheat it, this is a mechanical problem.

Why that setup didn't achieve it's goal? It was a false idea that reducing the heat would somehow magically increase belt traction. Heat does cause slip due to cavitation, but that's not going to increase the belt traction beyond normal levels. You want the oil temperature not too cold and not too hot, so I'd say that 194*F is a pretty darned good target if I had to pick one.

I'm not saying the external coolers aren't needed. I'm saying lot's of times it's a crutch for an existing problem. Fix the problem first......then add the cooler and you now have an even better setup.

 

[Bargeld]

Just one of the reason I haven't done am external CVT cooler. The risk of introducing problems is more than the return of the cooler.

Regular & early fluid swaps at a dealership are a better solution for me.

 

[squirtbrnr]

Same here. I thought about doing an external cooler because I’m tuned but instead I stick with CVT drain and fills at the dealership every ~40k miles. The added risks of modifying the existing CVT fluid system outweigh the rewards for me.

 

[Jaxxa]

I feel like that is a very detailed explanation as to why we all have seen such little returns with our CVT coolers. I will say that when I was having my beehive cooler swapped out I suggested to the tech to swap in a new CVT oil filter, and they said I probably didn't need it, and I'm thinking I probably should have pushed for it a bit more.

 

[pboglio]

Should've done the filter. I have pictures of mine off the car, the restriction and debri was insane on that clogged filter. Not sure if it was the AMSOIL or new filter but either way my temps dropped from about 110*C to a max of about 103-104*C. But it would take an hour of solid expressway driving for that to happen. I'd consider 98*C about perfect, so for a worn out CVT I'd say that was a good improvement. That's with the factory cooling setup.

I was thinking maybe running a 2 thermostats running in parallel might increase water flow thru the stock beehive cooler. No idea if it would work but it I'd be curious as the water flow increase would improve cooling. Again, I'll be running a custom cooler but it'll still be water cooled, just way more efficient.

 

[Jaxxa]

Should've done the filter. I have pictures of mine off the car, the restriction and debri was insane on that clogged filter. Not sure if it was the AMSOIL or new filter but either way my temps dropped from about 110*C to a max of about 103-104*C. But it would take an hour of solid expressway driving for that to happen. I'd consider 98*C about perfect, so for a worn out CVT I'd say that was a good improvement. That's with the factory cooling setup.

That's actually insane, 98C is like 208F and I thought that was super hot. I personally have not witnessed my CVT temp go over 210F, even on a super hot day, or offroading. Maybe my CVT isn't too bad off. I'll still bring up the filter when I schedule my next drain and fill.

 

[pboglio]

Well, here is a general temperature guideline for auto transmissions. I'll be running a 195*F oil thermostat or something similar. I'd say then anything lower than 175*F you probably don't want to run based off the chart. The oil cooler will dictate how cold you can run, regardless of the thermostat. Under max power, you simply may not have a choice but to deal with higher temps. My cooler design will keep the temps at about 98*C (208*F) maximum because that is the limit of the cooling at that horsepower level. Most situations during cruise I could keep it as low as the radiator temps of 183*F if I played with the oil thermostat because I'll still be using water cooling.

When I tore apart my CVT the clutches were burnt and fried due to slippage and high temps. Maybe running at 175*F would have extended that life dramatically.