Had my first AHC Issue today (2013 LX570)... Brrr, it's cold (1 Viewer)

[CanadianRockyCruiser]

I'm a big fan of AHC and have always maintained the system myself on my lX470 and now LX570 vehicles. Today, I had my first real hiccup in my AHC history and it made me wonder a bit about the chemistry of AHC fluid and the rubber (is it rubber?) membranes in our AHC globes.

It's getting a bit chilly up here in the great-white north, with the wind-chill getting down to -49° C (Actual temp is currently -34° C). Last night I parked outside and plugged in my block heater and battery warmer. I also had parked the vehicle in easy access mode (drop to low-mode when engine is turned off). Admittedly, I don't recall the last time I've exposed the LX to this level of cold for this long.

This morning, I toss the kids in the back and head out for daycare/work and the LX doesn't want to go into high mode. The suspension was bouncing like a kangaroo over bumps and speedbumps and try as she might, the little LX couldn't get to AHC "N" mode, all the way to work (only 5km distance, at slow speeds <40km/hr). After being parked in a toasty underground garage at 15° C for a few hours, I headed back to check on my dear LX. Toasty and warm, I fire up the LX and all is well and right as rain in suspension-land: AHC becomes compliant and hops right back into "N" with the flick of a switch. Take her for a spin around the block, and it's like she hadn't missed a beat.

My questions here are: What elements do you think are experiencing the extreme cold weather hardship? Is it the AHC fluid? The globes? Maybe too low of voltage from the electrical system to run the pump?

I'm wondering what temp the AHC fluid freezes at. I'm also wondering what type of "rubber" is used inside the AHC globes. I appreciate any of your insights AHC gurus!

 

[grinchy]

Perhaps the conditions to raise weren’t met and it has nothing to do with system function?

 

[CanadianRockyCruiser]

Perhaps the conditions to raise weren’t met and it has nothing to do with system function?

Possible... but usually, she hops back up to "N" after driving at 12km for a short while. I also toggled the switch to "N", to no avail.

 

[grinchy]

I’m thinking one of the sensors (brake, door closed, etc) wasn’t reporting.

 

[lx200inAR]

Possible... but usually, she hops back up to "N" after driving at 12km for a short while. I also toggled the switch to "N", to no avail.

When you toggled the switch, did you get the blinking arrows in the dash?

 

[LX4x4]

Just googled says Hydraulic fluid freezes at -10F.
So actually not sure how the car stops from damaging the pump or system in cold weather.
Why does it need to be in high mode or low mode? Do you park in low?

 

[TeCKis300]

Whew, that's chilly!!

AHC fluid from my understanding is largely mineral oil based. From a quick search, there's some variation in freezing point of the fluid depending on formulation but a general threshold is about -30F/-22C, and you were well below that!

Sounds to me like the fluid needed time to warm up.

 

[CanadianRockyCruiser]

Yeah, in the future, Ill turn off "Easy access Mode" and keep her in "N" when it's this cold.

 

[lx200inAR]

From the FSM:

b. Conditions when vehicle height control stops:

• When the stop light switch is on, after operating for a few seconds, control stops. However, when the transfer is in the L4 position, control does not stop.
• When the vehicle is driving on an uneven road and the vehicle height increases or decreases rapidly due to bumps, etc., control stops.
• On an inclined road, when the inclination is approximately 20° front to back or approximately 17° side to side, control stops.
• When the height control pump and motor continuously operates for approximately 85 seconds, control stops.
• When the oil temperature is -30°C (-22°F) or less, or 100°C (212°F) or more, control stops.

Luckily -30 is within the range of the sensor....guess that means it's a 16bit value..

Oil Temperature Sensor
Fluid temperature sensor reading /
min.: -3276.8°C (-5866.24°F)
max.: 3276.7°C (5930.06°F)

 

[CanadianRockyCruiser]

I’m thinking one of the sensors (brake, door closed, etc) wasn’t reporting.

Could be the case!

 

[CanadianRockyCruiser]

When you toggled the switch, did you get the blinking arrows in the dash?

It showed the up arrow moving from L to N, but it just never got there.

 

[CanadianRockyCruiser]

From the FSM:

b. Conditions when vehicle height control stops:

• When the stop light switch is on, after operating for a few seconds, control stops. However, when the transfer is in the L4 position, control does not stop.
• When the vehicle is driving on an uneven road and the vehicle height increases or decreases rapidly due to bumps, etc., control stops.
• On an inclined road, when the inclination is approximately 20° front to back or approximately 17° side to side, control stops.
• When the height control pump and motor continuously operates for approximately 85 seconds, control stops.
• When the oil temperature is -30°C (-22°F) or less, or 100°C (212°F) or more, control stops.

Luckily -30 is within the range of the sensor....guess that means it's a 16bit value..

Oil Temperature Sensor
Fluid temperature sensor reading /
min.: -3276.8°C (-5866.24°F)
max.: 3276.7°C (5930.06°F)

There's a winner. Thank you for the info! It's rare that the temperature drops that low, and even more rare that the temperature drops that low AND I need to drive somewhere. Usually I go into hermit-mode and hide under a blanket at -25°C...

I'll turn "off" AHC and "easy access mode" until it warms up on Monday.

I kind of loathe stating this, but perhaps I should be running Ravenol with a pour-point of -60°C:

RAVENOL AHC Active Height Control Fluid

RAVENOL AHC Active Height Control Fluid is a full synthetic hydraulic fluid based on PAO (Poly-alpha-olefin) and Ester. RAVENOL AHC Active Height Control ...

www.ravenol.de

I might put some Toyota AHC in a beaker and leave it outside tonight to see if it solidifies or becomes very viscous...

 

[doru]

Even if you change the fluid the control will still stop at -30. So not worth the trouble of chaining the fluid.

 

[CanadianRockyCruiser]

Even if you change the fluid the control will still stop at -30. So not worth the trouble of chaining the fluid.

Fair point... I should just never drive at -30C....but even if the ahc isn't active, at least the fluid will be liquid state. -30 doesnt come up often, but we do get temperatures well velow -20C every winter. If an alternative fluid can still pour at -60, it might be a better option for AHC in very cold places. Any Ravenol users out there?

 

[jlinc50]

Fair point... I should just never drive at -30C....but even if the ahc isn't active, at least the fluid will be liquid state. -30 doesnt come up often, but we do get temperatures well velow -20C every winter. If an alternative fluid can still pour at -60, it might be a better option for AHC in very cold places. Any Ravenol users out there?

I have a similar issue not related to temperature since I live in Florida. I’ve owned my 2013 LX for a year. Everything works as it should except AHC would never lock in to high or low. It will raise but not lock in. I would need to put back in N and drive it above 30MPH for it to return to N. I flushed the system with OEM fluid and bleed all bleeders as recommended. But still no change in ability to lock in H or L. Truck seems fine as far as ride quality and no warning lights or codes. Any ideas would be much appreciated. Considered taking it to dealer for diagnostic help but I’m afraid most likely they won’t know anymore about the issue than I do then start throwing parts at it. Thanks

 

[shunra]

I am in Calgary as well and I just saw this, but the exact same thing happened to me during the same cold snap. Probably the same day as you. I had mine in easy access mode as well, and it would not raise. I was able to confirm that the pump was not trying to run, so I assumed it was some kind of software lockout due to the cold. It warmed up a bit later in the day and everything started working as it should. For what it is worth, given that both of us saw the same thing in the same city, probably on the same day, my guess it is operating as designed. This gives me some peace of mind.

 

[finboy]

I am in Calgary as well and I just saw this, but the exact same thing happened to me during the same cold snap. Probably the same day as you. I had mine in easy access mode as well, and it would not raise. I was able to confirm that the pump was not trying to run, so I assumed it was some kind of software lockout due to the cold. It warmed up a bit later in the day and everything started working as it should. For what it is worth, given that both of us saw the same thing in the same city, probably on the same day, my guess it is operating as designed. This gives me some peace of mind.

Calgary based here as well, bought my truck just after the cold snap but definitely will keep easy access mode in mind for next year.

 

[Nothinghead]

Just googled says Hydraulic fluid freezes at -10F.
So actually not sure how the car stops from damaging the pump or system in cold weather.
Why does it need to be in high mode or low mode? Do you park in low?

If we assume it’s not pure hydraulic fluid, the actual freezing point is likely below -10°F and possible at or near the -22°F referenced in the FSM. Luckily, such fluids don’t expand when freezing like H2O does so it’s unlikely to stress or damage anything. Of course, trying to move the “fluid” when it is solid will quickly damage things.

When I had mine below 30°F, it took about 20 minutes and 10 miles’ driving in L for the pump to kick on and height to return to N.

 

[CanadianRockyCruiser]

This weekwnd I was in Saskatchewan and it was -29C on the dash. AHC functioned fine.

Previously, I left 50ml outaide in a beaker at -38C for 8 hours and it didnt freeze. It was definitely a bit thicker at that temperature, but still liquid.

I dont think the viscosity or freezing point of AHC fluid is much of an issue. I think its just important to keep in mind that if the temperature drops to -30C, the pump won't function. If its going to be below -20C, my precaution will be to avoid putting the system in low.