Radiator flush and cap removal - overheating CVT

[funkee]

Hey folks,

I am taking a road trip at the end of June to Vegas, and I'm very concerned about overheating - especially because I have a CVT.

I realized that I hadn't flushed the radiator since I bought it, and I assume the previous owner did not do so because Nissan's coolant is marketed for long life. The car is an '08 with about 35,000 miles now.

I bought a coolant wetter to help make the coolant more effective, and was considering using a higher water to coolant ratio - about 70% water, 30% coolant. Before flushing it myself, I checked out the service manual (http://www.nicoclub.com/FSM/Altima/2008/co.pdf p.32-33) and they advise using vacuum tools when flushing the radiator - things that I don't have.

Have any of you flushed the radiator yourselves? If so, did you use any special tools? I figured I could just open the radiator cap and the drain plug. Flush it with distilled water and run the engine a few times in between. Then fill it up with the water/coolant/wetter mixture. But then I ran into a problem. I can't get the radiator cap off. I can loosen it, but it's stuck. There are two edges that are crimped down that help the cap make a seal, and prevent it from turning too far. But no matter how much jiggling I do, I can't get the cap off. I don't want to force it, because I don't want to damage the cap. Any suggestions?

Thanks!

[mmkeller]

Did you push down on the cap, then turn?

[rcboy514]

I haven't read the manual or talked to a dealer, but usually that's all you do when flushing the system....drain it and run water (water hose) through it until clear water comes out of the drain hole (doesn't have to be distilled at this point). Then just refill the system with 50/50 distilled/coolant. I'm not sure if our car will auto bleed the system, but I would assume they do.

The way I usually do it if there isn't a bleed screw is roughly this...

-refill system via the overflow reservoir until it's at the max level

-Start the car ***EDIT (turn heat on high and fan on low) and let it idle with the filler cap OFF until it reaches operating temp continually checking the coolant level and adding more as needed.

-Go for a 5-10 minute drive and make sure it doesn't overheat.

[stevewaclo]

Funkee,

How as the Vegas trip and your coolant change project?

Your post got me thinking about coolant service interval and I located this (too lazy to dig out my manual :-) :

http://www.nissanextendedwarranty.com/o ... _N_SMG.pdf

After carefully paging through all the service interval pages (in both directions) found the first reference to coolant flush and fill (vs check and top off) on page 51 (please double check me). There it stated flush and refill at, wait for it, 120k or 96 months (!!!). A whole new meaning to "long life" coolant.

Regarding special equipment for the job, when my time/mles come around, believe I'll let a dealer handle it. An air bubble in a critical location (near an exhaust valve?) could be disastrous.

Best wishes

[funkee]

I forewent the radiator flush after reading the same thing. The dealership wanted $130 for the job, so I passed.

But the car struggled in the desert heat. Even with an UpRev tune, the ECU really pulled the power down to protect the transmission.

After driving a few hours in 110F heat, I could not downshift below 6th in manual mode. I couldn't accelerate past 80mph, or get above 3,000RPM. I must have lost 70-80% power because of the heat. Despite that, the temperature gauge never budged. I guess our cars are really, really heat sensitive. I had to make multiple stops to let the engine bay cool down.

Another forum member got on a dyno with a warm vehicle (Maxima) and posted some really weak numbers. The shop owner postulated that it is because of the heat. And I can confirm that's the case.

I think I will invest in a transmission intercooler, like the ones the boosted members have. It's cheap, and probably the best mod for power considering how much is lost on a hot day. A better coolant mix with a wetting agent should also help.

I'm also contemplating putting on heat reflectors in the engine bay, some light weight heat sinks on the engine block, and build some ramps to help air escape to the underside of the car. I thought about hood vents and fans, but increasing the pressure in the engine bay behind the radiator, makes the radiator less effective. Ideally the pressure in the engine bay should be as low as possible, to help pull air through the radiator and hopefully out underneath the car.

[stevewaclo]

transmission inter cooler sounds like an excellent idea, even if it turns out not to solve your current problem.

Other than the CVT, my '08 6sp is identical and has soldiered on @80mph+ with full a/c and outside temps in the high 90's.

Just a thought. Have you considered hooking up a system to spray water on your existing transmission cooler and see what develops? Perhaps some small, adjustable irrigation spray heads and plastic plumbing connected to a (passenger operated) squeeze bottle. Evaporative effect at the transmission cooler should drop the temperature of fluid returning to the CVT enough to tell you if high temperatures there are the problem. If you are not into plumbing, maybe a buddy strapped onto the hood with a spray bottle and...oh, never mind :-).

Also, would an inexpensive OBDII reader allow you to access CVT temps? If indeed that is the source of your performance issue, the temp must be read and relayed to the CPU somehow, and may be available as a direct reading. Of course if my speculation is correct, why is your MIL lamp not coming on? Seems unlikely the CPU would simply cut power on high CVT temp, without setting a code.

[funkee]

I remember reading posts from other members, who reported similar issues with their CVTs. One member specifically noted how he was unable to downshift in manual mode.

I've driven at high speed, with AC on full blast, for more than an hour at 90+ heat. That wasn't a problem. But the effect of 3 hours in Death Valley heat of 110F+ with long hills at high speed was very obvious. Oddly enough, no lights came on during that time. I think that's because the car cut power before it let me get it to that point. If it hadn't, I would've probably triggered one of the lights by pushing the throttle until it overheated.

As far as spraying a bit of water... that's an interesting idea. Here in the Bay Area where I'm located, the weather is mild, and I wouldn't need such drastic measures. I'm not familiar with the aerodynamics of an engine bay, but I suspect that I would want a vented hood to implement the spray bottle method. Otherwise a lot of the steam would collect near the top of the engine bay, and wouldn't necessarily be forced out. I wouldn't want steam there... since I don't have a hydro-shield on my K&N, I imagine a good amount would be forced into the engine.

But hey, why stop at water? Why not alcohol? Liquid nitrogen? Or a can of compressed air?

[Throckmorton]

The Nissan Altima owner’s manual has the answer to this question.

5-16 Starting and driving

High fluid temperature protection mode

This transmission has a high fluid temperature protection mode. If the fluid temperature becomes too high (for example, when climbing steep grades in high temperature with heavy loads, such as when towing a trailer), engine power and, under some conditions, vehicle speed will be decreased automatically to reduce the chance of transmission damage. Vehicle speed can be controlled with the accelerator pedal, but the engine and vehicle speed may be limited.

Fail-safe

If the vehicle is driven under extreme conditions, such as excessive wheel spinning and subsequent hard braking, the fail-safe system may be activated. The MIL may come on to indicate the fail-safe mode is activated, see “Malfunction indicator light (MIL)” in the “Instrument and controls” section This will occur even if all electrical circuits are functioning properly. In this case, place the ignition switch in the OFF position and wait for 10 seconds. Then push the switch back to the ON position.
The vehicle should return to its normal operating condition. If it does not return to its normal operating condition, have a NISSAN dealer check the transmission and repair if necessary.

When the high fluid temperature protection mode or fail-safe operation occurs, vehicle speed may be gradually reduced. The reduced speed may be lower than other traffic, which could increase the chance of a collision. Be especially careful when driving. If necessary, pull to the side of the road at a safe place and allow the transmission to return to normal operation, or have it repaired if necessary.

[AlexN09]

I often fear that my car will kill me going into limp mode. I once pulled out in front of oncoming traffic to turn left across a road and my car went into limp mode. I was expecting the car to accelerate quickly and didnt hav much time to get across the road. I was flooring it ad my car was crawling across the street. Oncoming traffic luckily was able to brake in time to not kill me.

[funkee]

Was it hot out? That sounds absurdly dangerous... I can imagine a fat lawsuit against Nissan for something they don't consider a defect.

[AlexN09]

No it wasn't hot out and I don't think it was an overheating issue. I believe that this happens in my car when I change between manual and auto modes rapidly/nonsensically. If I remember correctly I was braking somewhat hard in manual mode using engine braking as well as brakes, switched to auto while I was coming to a stop, then back into manual in a short amount of time to take off again. My car did not really respond much at all until I hit thirty five mph or so and then it regained torque and power like nothing ever happened.

This exact scenario has occurred many times (although less than ten times) at red lights shifting between auto and manual modes.

[funkee]

I have a theory of what happens.

When you switch to CVT mode, the transmission takes the tallest gear ratio, which is equivalent to 6th in manual mode. When you press the throttle, the gear ratio changes, and continues to change as you gain speed or vary the throttle. When you switch from CVT to manual mode, it downshifts to a lower simulated gear ratio. It seems that when you switched to CVT mode, the transmission picked the highest gear ratio. But when you switched back to manual mode, the transmission got stuck in 6th gear.

I suspect that if you floored the throttle past the click, the transmission will downshift and correct itself. It normally downshifts in manual mode if you press the pedal down all the way down.

[nismogirl92]

I forewent the radiator flush after reading the same thing. The dealership wanted $130 for the job, so I passed.

But the car struggled in the desert heat. Even with an UpRev tune, the ECU really pulled the power down to protect the transmission.

After driving a few hours in 110F heat, I could not downshift below 6th in manual mode. I couldn't accelerate past 80mph, or get above 3,000RPM. I must have lost 70-80% power because of the heat. Despite that, the temperature gauge never budged. I guess our cars are really, really heat sensitive. I had to make multiple stops to let the engine bay cool down.

Another forum member got on a dyno with a warm vehicle (Maxima) and posted some really weak numbers. The shop owner postulated that it is because of the heat. And I can confirm that's the case.

I think I will invest in a transmission intercooler, like the ones the boosted members have. It's cheap, and probably the best mod for power considering how much is lost on a hot day. A better coolant mix with a wetting agent should also help.

I'm also contemplating putting on heat reflectors in the engine bay, some light weight heat sinks on the engine block, and build some ramps to help air escape to the underside of the car. I thought about hood vents and fans, but increasing the pressure in the engine bay behind the radiator, makes the radiator less effective. Ideally the pressure in the engine bay should be as low as possible, to help pull air through the radiator and hopefully out underneath the car.

Story of my life!!!! I am in Florida though. Thanks for sharing!

[seldomseen]

Story of my life!!!! I am in Florida though. Thanks for sharing!

Nissan's CVT can be an down right odd depending on temperature. During the cold winter months in New England the CVT operates rough until it's within it's normal operating temperature. And depending on how cold the weather is....it can take sometime to reach normal operating temperature. Other than that the CVT is a treat and is well mated to the 3.5 litre engine.