Definitive list of AHC maintenance items (7 Viewers)

[NorCalFJ100]

Hey crew, need some real time help. I am in the middle of replacing my front globes. The driverside is hitting the accumulator solenoid as I loosen it. Feels like it is getting close to coming out, but its really digging into the wires off the solenoid. I can't find that anyone else had trouble with this for some reason.

Anyone? I assume I can just pop off the solenoid, but it looks like a very thin wrench is needed. Ugh.

 

[IndroCruise]

This link may help ....

replacing AHC globes/accumulators

 

[Cetus]

Happy Thanksgiving everyone!

In need of some help. I ran techstream and started around 7.7 Mpa-G in the fronts and cranked the TBs about 9 turns clockwise. Now my pressures are at 6.7 Mpa-G but it's still boucy on the dips and still feel the cracks on the road. I've checked tire pressures and they are good, and right now getting about 7-8 graduations from low to high. Any suggestions or ideas on what the issues are? You think it's about time to replace the globes? Thanks!

2007 LX - 152K

Both Fronts - 19 1/4"
Both Rears - 20"

Front neutrals - 6.7 Mpa-G
Rear neutrals - 6.7 Mpa-G
Accumulater pressure - 10.2 Mpa-G

 

[IndroCruise]

Happy Thanksgiving everyone!

In need of some help. I ran techstream and started around 7.7 Mpa-G in the fronts and cranked the TBs about 9 turns clockwise. Now my pressures are at 6.7 Mpa-G but it's still bouncy on the dips and still feel the cracks on the road. I've checked tire pressures and they are good, and right now getting about 7-8 graduations from low to high. Any suggestions or ideas on what the issues are? You think it's about time to replace the globes? Thanks!

2007 LX - 152K

Both Fronts - 19 1/4"
Both Rears - 20"

Front neutrals - 6.7 Mpa-G
Rear neutrals - 6.7 Mpa-G
Accumulater pressure - 10.2 Mpa-G

Quoted neutral pressures are within the specified ranges if vehicle is at correct height -- front: 6.4 to 7.4 Mpa; rear: 5.9 to 7.0 Mpa. The vehicle does appear to be a little low compared to the recommended distances hub-to-fender of 19.75" at front and 20.50" at rear. Neutral pressures will increase somewhat if these heights are adjusted, front then can be readjusted at torsion bars, rear may require new springs or spacers to reduce neutral pressure.

Test result of 7 to 8 graduations at AHC tank appears borderline if done at correctly with vehicle height and neutral pressures within specification and AHC fluid in good condition. Just a fluid change/flush may help as a first step but one or more of the four 'globes' (called 'gas chambers' in FSM) may have reached their 'use-by date', meaning aging and inevitable deterioration of the membrane in one or more 'globes' has led to loss of nitrogen with vehicle now riding mainly on the springs or torsion bars and with reduced damping, giving a bouncy ride. If so, replacement of all 'globes' is the next step. New 'globes' should show ~14 graduations at the the AHC tank.

As well as the entirety of this thread, a review of Updating AHC system also may be helpful.

Late edit: Worth noting that FSM specification for rear neutral pressures in unloaded condition are:
5.6 to 6.7 Mpa without sub-fuel tank and with fuel tank full
5.9 to 7.0 Mpa with sub-fuel tank with both fuel tanks full (applies to my vehicle)

 

[Cetus]

Quoted neutral pressures are within the specified ranges if vehicle is at correct height -- front: 6.4 to 7.4 Mpa; rear: 5.9 to 7.0 Mpa. The vehicle does appear to be a little low compared to the recommended distances hub-to-fender of 19.75" at front and 20.50" at rear. Neutral pressures will increase somewhat if these heights are adjusted, front then can be readjusted at torsion bars, rear may require new springs or spacers to reduce neutral pressure.

Test result of 7 to 8 graduations at AHC tank appears borderline if done at correctly with vehicle height and neutral pressures within specification and AHC fluid in good condition. Just a fluid change/flush may help as a first step but one or more of the four 'globes' (called 'gas chambers' in FSM) may have reached their 'use-by date', meaning aging and inevitable deterioration of the membrane in one or more 'globes' has led to loss of nitrogen with vehicle now riding mainly on the springs or torsion bars and with reduced damping, giving a bouncy ride. If so, replacement of all 'globes' is the next step. New 'globes' should show ~14 graduations at the the AHC tank.

As well as the entirety of this thread, a review of Updating AHC system also may be helpful.

Thank you for the help. I have already flushed the system by going with PADDO's method and all the fluid looks clean. I'll try to adjust the height to see of that helps. As you mentioned the graduations are little low so maybe the globes are done.

 

[Travis Bickle]

Thanks to everyone for all the info in this thread...

Just getting around to checking/baselining/maintaining my truck, I replaced a damaged sensor arm and cranked my tbars (1.5") which helped out my pressures quite a bit, got the truck sitting properly again it was saggy in the front. At my year/mileage I believe my rear springs have already been replaced, they don't look old and my rear pressures are pretty ok.

Next I'll be replacing all my shock bushings, upper mounts and fluid flush.

Before

After

I also made a youtube video for quick referencing

 

[Jczajka]

I unplugged the sensor and the specs were the same. So I definitely need new springs.

My question is should I go with OE LX AHC springs or King Springs? I have a Falken Wildpeak AT3W 275/70R18 as my spare which is 60lbs, a 1up 3 bike hitch rack that weighs ~70lbs, and the storage platform and gear that is probably 160-200lbs. So some extra weight for daily driving, but not hardcore off-road gear.

From reading some of @PADDO notes it seems rear OE springs and maybe 30-40mm spacers to bring pressure in specs with the extra weight or King springs and no spacers. Wondering what the King springs ride is for a pretty much stock truck.

View attachment 2133259

I installed my new Lexus AHC springs with 30mm spacers on top. I used spring compressors, because I had them With the temp sensor unplugged and all the new stuff in I'm still seeing high pressure in the rear. 6.9 Front, 7.6 Rear now. Measured and readjusted the TB a couple of times and this was the best I could get. Hard to find a really level spot to check, I'm always worried I'm not on a flat enough spot.

Kinda bummed, I thought it would be much lower. Any ideas @PADDO ?

The new springs looked exactly the same as the old ones, side by side, but I know that's not and indication of wear. I thought it would be more dramatic old vs. new. No history of springs ever being replaced. I installed new Plieades globes, new shock cushions and bushings, and a nice bleed with Lexus AHC fluid prior to installing the new springs.

Should I have bought King Springs instead?

Anyone want to buy new AHC Springs and/or 30mm spacers?

 

[Jczajka]

I installed my new Lexus AHC springs with 30mm spacers on top. I used spring compressors, because I had them With the temp sensor unplugged and all the new stuff in I'm still seeing high pressure in the rear. 6.9 Front, 7.6 Rear now. Measured and readjusted the TB a couple of times and this was the best I could get. Hard to find a really level spot to check, I'm always worried I'm not on a flat enough spot.

Kinda bummed, I thought it would be much lower. Any ideas @PADDO ?

The new springs looked exactly the same as the old ones, side by side, but I know that's not and indication of wear. I thought it would be more dramatic old vs. new. No history of springs ever being replaced. I installed new Plieades globes, new shock cushions and bushings, and a nice bleed with Lexus AHC fluid prior to installing the new springs.

Should I have bought King Springs instead?

Anyone want to buy new AHC Springs and/or 30mm spacers?

View attachment 2154377

View attachment 2154378

Anyone have any thoughts on this?

Front at 19.75" rear at 20.5", level side to side, pressure in the front dialed, but rear still high.

Guess I need King Springs????

 

[JMC3]

Thanks to all of the AHC gurus out there! @PADDO @uHu especially. I have read and tried to digest all of this string. and taken the recommended steps that are within my limited mechanical capabilities, except for messing with the height sensors. I have bled the AHC system, stock rear springs installed today and I tweaked the Torsion bars to arrive at the vales listed above.

The truck is riding well (much better), but there are two things I would like some advice on :

1) I am still a little low on actual height. Would you recommend that I make adjustments to the height Sensors?
RF= ~19.5"
LF= ~19.5"
LR= ~20.5"
LR= ~20.25"

2) If I make the height adjustment, would i expect the Rear Neutral Pressure to come down at all? The new springs had very little impact on the neutral pressures.

3) Oh, and one more thing: How do I "zero" the steering angle on my 2007? will that change the values or the drive quality?

Thanks!

 

[Jczajka]

Thanks to all of the AHC gurus out there! @PADDO @uHu especially. I have read and tried to digest all of this string. and taken the recommended steps that are within my limited mechanical capabilities, except for messing with the height sensors. I have bled the AHC system, stock rear springs installed today and I tweaked the Torsion bars to arrive at the vales listed above.

View attachment 2171771
The truck is riding well (much better), but there are two things I would like some advice on :

1) I am still a little low on actual height. Would you recommend that I make adjustments to the height Sensors?
RF= ~19.5"
LF= ~19.5"
LR= ~20.5"
LR= ~20.25"

2) If I make the height adjustment, would i expect the Rear Neutral Pressure to come down at all? The new springs had very little impact on the neutral pressures.

3) Oh, and one more thing: How do I "zero" the steering angle on my 2007? will that change the values or the drive quality?

Thanks!

Zero is just centering the wheel until it hits 0 while doing the test.

I bled my freshly replaced globes, installed new stock LX rear springs, and leveled everything. I still have high rear pressures. I am thinking I need King Springs, but have not got any answers from the forum when I asked above.

I'm thinking new heavier springs for mine.

 

[Cetus]

Zero is just centering the wheel until it hits 0 while doing the test.

I bled my freshly replaced globes, installed new stock LX rear springs, and leveled everything. I still have high rear pressures. I am thinking I need King Springs, but have not got any answers from the forum when I asked above.

I'm thinking new heavier springs for mine.

Did you replace your globes because the ride was bouncy and harsh? Those are the symptoms I'm getting so planning on doing them soon. Hoping that will fix the issues.

 

[Jczajka]

Did you replace your globes because the ride was bouncy and harsh? Those are the symptoms I'm getting so planning on doing them soon. Hoping that will fix the issues.

Yeah, Plieades globes and bouncyness is gone. I can feel the difference in settings between sport and comfort, but they're subtle.

Pressures on the front are great, but still high in the rear even with new stock LX springs and 30mm spacers. I carry extra gear in the back and have a 3 bike hitch rack, So I guess I need King Springs. I assumed with fresh springs & spacers I'd be close to stock pressure, but I guess not.

 

[Cetus]

Yeah, Plieades globes and bouncyness is gone. I can feel the difference in settings between sport and comfort, but they're subtle.

Pressures on the front are great, but still high in the rear even with new stock LX springs and 30mm spacers. I carry extra gear in the back and have a 3 bike hitch rack, So I guess I need King Springs. I assumed with fresh springs & spacers I'd be close to stock pressure, but I guess not.

That's great. Gives me confidence to so the same.

 

[uHu]

My remaining issue is that the vehicle takes 28 to 30 seconds to lift from AHC “LO” to AHC “N” while FSM suggests 10 to 15 seconds. Partial blockage somewhere? Friction between rear springs and internal airbags slowing the lift? AHC pump and/or the long cylindrical height accumulator nearing end-of-life?
View attachment 2134147

Revisiting your post from last year @IndroCruise . Did you get any further with the AHC?
I see two issues, which might be connected. One is the long lift time from Lo to N. The other is that your screen shots always show the height readings well under zero. 5 mm isn't that much, but always 5 mm lacking is not normal. The whole idea of the Automatic Height Control is that the pump lifts the car until the height sensors reach zero. For the fronts the values are averaged (if they are not too different), and the raising will stop when the average is zero. Normally it will stop within 1-2 mm above or below, both front and rear.

 

[JMC3]

Revisiting your post from last year @IndroCruise . Did you get any further with the AHC?
I see two issues, which might be connected. One is the long lift time from Lo to N. The other is that your screen shots always show the height readings well under zero. 5 mm isn't that much, but always 5 mm lacking is not normal. The whole idea of the Automatic Height Control is that the pump lifts the car until the height sensors reach zero. For the fronts the values are averaged (if they are not too different), and the raising will stop when the average is zero. Normally it will stop within 1-2 mm above or below, both front and rear.

@uHu, should the sum of the fronts and rears equal zero? Or should the sum of the fronts (L/R) equal zero? I've got the numbers below. My question was whether I should manually adjust the sensors as I am ~.5 inch low hub center to fender. If my front height sensors should add up to zero, then I am not in as good of shape as I thought I was...

I'm a newbie on this stuff. Sorry if this seems like a simple question or I am confusing the issue.

 

[uHu]

@uHu, should the sum of the fronts and rears equal zero? Or should the sum of the fronts (L/R) equal zero? I've got the numbers below. My question was whether I should manually adjust the sensors as I am ~.5 inch low hub center to fender....

The fronts should add up to around zero. Do you get these values each and every time you move from Lo to N? (On a horisontal, level surface)
Is it the front or the rear which is a half inch too low? If you adjust the sensor(s) to get up to spec height, your pressure will go up accordingly. Paddo has posted the relationship between height and pressure somewhere, iirc. If you do adjust, the values you read in TechStream after moving from Lo to N will be just the same as before, if everything is OK. I keep my rear about half an inch low to help with keeping the pressure within specs (or to be able to take more cargo).

 

[ticoman]

I finally got a reliable teckstream cable to run on Win 10 and thought I would tackle my AHC pressures before I install an ARB front bumper next week. I have read through the monster thread on "All things AHC, but they mostly deal with Gas engines and non dual tank versions. I know that the diesel model has heavier torsion bars but that is about all I know as different. Here is a shot of my pressures after L to N on fairly level ground. my rear is at 20" and the front is 19.5" with 3/4 full main and full aux tank.Can some one please tell me if I should be cranking my T bars to fit gas statistics or what? When I go from N to H , H flashes then goes back to N. If I turn the key off, then on again, it will be at H. I have an e copy of the 04 FSM but it does not cover the AHC system, is there an active link to one?. Sorry for the rambling. Thanks I appreciate your input.

 

[JMC3]

I want to try 30 mm spacers (packers) to reduce rear neutral pressures. What exactly am I buying and where do I get them? can someone point me in the right direction? THanks!

 

[nothappening]

I want to try 30 mm spacers (packers) to reduce rear neutral pressures. What exactly am I buying and where do I get them? can someone point me in the right direction? THanks!

Tough Dog Coil Spring Spacers

Toyota Land Cruiser Tough Dog Coil Spring Lift Spacers 30mm (1.18") tall polyurethane coil spring spacers 80 Series 100 Series 200 Series

trail-tailor.com

or

Slee - Toyota 80 Land Cruiser Suspension Spacers >> scroll to bottom and it's on the left.

 

[JMC3]

Thanks a bunch fijck! Ordered from Trail-Tailor.