replacing AHC globes/accumulators (3 Viewers)

[IndroCruise]

Good question @BullElk!

Short answer: It is not known whether the picture attached to Post #205 above represents the membrane position in a good ‘globe’.

Long Answer: It seems likely that cutting process involved making the cutaway would have had a tearing effect on the rubber-resin-rubber sandwich which makes up the membrane. Nevertheless, I think the membrane in the cutaway is in its natural, as-manufactured position, without the effects of nitrogen gas on one side and AHC Fluid on the other side.

The position shown in the cutaway is similar to the position shown in the diagrams in the FSM.

I have a set of old ‘globes’ – two Front and two Rear – so I measured them this morning and marked-up the measurements of their membrane positions on the FSM diagram below.

However, the marked-up diagram is illusory because, while the measurements are accurate, the measurements on the amended diagram are not to scale and do not show the distended membrane position accurately, as caused by the residual nitrogen gas. So this exercise really does not tell us much.

The old ‘globes’ came off my vehicle when the HI/LO Test showed 8 graduations. Even though the FSM says that this is the change-point for Australian vehicles (versus 7 graduations elsewhere), I could have left the ‘globes’ in place for longer. However, we were preparing for a long trip of ~6,500 kilometres (~4,000 miles), some of it along hot, rough, remote roads and trails across Australia while heavily loaded -- and so I decided on a precautionary early change-out of ‘globes’. We had a great trip without any mechanical dramas – but that is another story.

The point is that the old ‘globes’ still have considerable nitrogen pressure. The membranes in all my old ‘globes’ are visibly and measurably pushed way towards the fluid entry by this pressure. I would have to release the nitrogen pressure to see how the membrane position really compared with the cutaway picture. For now, I guess I will keep them 'as is' as a back-up set of ‘globes’!!

View attachment 2580250

View looking into fluid entry of old 'globe' showing distended membrane pushed forward by residual nitrogen pressure. It is likely that new 'globes' would look very similar out of the box.

View attachment 2580258

My notes below give a more considered answer than my answer way back in February at Post #209 to a question about 'globe' internals on this thread and on other threads.

It is also worth commenting on the so-called "Pencil Test": The FSM suggests that a new Rear 'globe' from the factory has a nitrogen gas pressure of 2.65 Mpa (384 psi). The 'globe' shown in my Post #209 in this thread was one of four which came off my vehicle when the 'HI/LO Test' gave a difference of 8 graduations at the AHC Tank. All 'globes' were still strong -- early change-out was a precaution for reliability in advance of a series of very long trips. Let's guess that this 'globe' had deteriorated to about half the original factory nitrogen gas pressure, say, 1.32 MPa or 192 psi. None of my pencils will make an impression when pushing against anything near 192 psi. For example, compare it with how hard it is to push a pencil into a tire with only 40 psi. The "Pencil Test" might indicate a ruptured 'globe' with no pressure behind the membrane -- but that is about the limit of the usefulness of the "Pencil Test". Measurement of nitrogen gas pressure remaining in a used 'globe' is not easy and would require a device such as that proposed by @suprarx7nut in his thoughtful Post #379 in this thread or a device similar to those used by Citroen people as mentioned on various websites.

More on 'globe' internals:

 

[Ossy]

Real time question here- I am currently changing out my globes and all is going well but I just realized I don't have anything like a turkey baster to suck the fluid out of the reservoir. This fluid is approximately 3 months old, so it should be relatively clean right? How can I completely bleed the system without sucking the fluid out of the reservoir, any ideas?

 

[FxFormat]

Real time question here- I am currently changing out my globes and all is going well but I just realized I don't have anything like a turkey baster to suck the fluid out of the reservoir. This fluid is approximately 3 months old, so it should be relatively clean right? How can I completely bleed the system without sucking the fluid out of the reservoir, any ideas?

Should be fine, 3 months old, just leave it in there. But if you really want it out, then put new globes in, start the truck and let fluid go into the lines and stuff, turn off truck and open bleeder valve, that'll release some fluid. Do that for front and rear, don't let reservoir run dry though.

 

[IndroCruise]

Should be fine, 3 months old, just leave it in there. But if you really want it out, then put new globes in, start the truck and let fluid go into the lines and stuff, turn off truck and open bleeder valve, that'll release some fluid. Do that for front and rear, don't let reservoir run dry though.

Or consider a syphon from the AHC Tank .....




It is not just about a fluid change -- an investment in new 'globes' seems worthy of the best possible effort to clean out air, sludge, oxidised particles etc, etc, which almost certainly are hiding in the system, especially at the extremities in the 'Shock Absorbers', in the 'Height Control Accumulator' and along some of the lines. It is not possible to 'flush' the system from one end to the other like a brake system, so the process relies on progressive dilution of 'bad stuff' with 'good stuff', ideally over multiple cycles. This not helped by use of existing fluid -- who knows what the existing fluid has picked up in the system? The object is to reduce the risk of air locks and sludge etc causing blockages or impeding flow at the tiny orifices and valves, particularly in the Control Valve Assembly, Damping Force Control Actuators and the AHC Pump. This is the reason for the explanation and recommendations back at Post #361 in this thread. Anyway, it is the Owner's choice of course ......

 

[Ossy]

Or consider a syphon from the AHC Tank .....




It is not just about a fluid change -- an investment in new 'globes' seems worthy of the best possible effort to clean out air, sludge, oxidised particles etc, etc, which almost certainly are hiding in the system, especially at the extremities in the 'Shock Absorbers', in the 'Height Control Accumulator' and along some of the lines. It is not possible to 'flush' the system from one end to the other like a brake system, so the process relies on progressive dilution of 'bad stuff' with 'good stuff', ideally over multiple cycles. This not helped by use of existing fluid -- who knows what the existing fluid has picked up in the system? The object is to reduce the risk of air locks and sludge etc causing blockages or impeding flow at the tiny orifices and valves, particularly in the Control Valve Assembly, Damping Force Control Actuators and the AHC Pump. This is the reason for the explanation and recommendations back at Post #361 in this thread. Anyway, it is the Owner's choice of course ......

Great write up! Ended up getting a $10 fluid extractor thingy from autozone

 

[Red Beard]

I just completed replacing all 4 globes. Got my globes from Impex. Here are the steps to replace them based on the @PADDO's method shared in this thread earlier here. Sharing as it might help others. Apologies if this is redundant but I couldn't find a clear step by step.

• Engine On
• Drop to L
• Engine Off
• Bleed all 5 bleeders to where fluid stops flowing (about 1 liter). Truck will be on bump stomps
• Close all bleeders
• Suck all fluid out of reservoir with baster or something
• FILL reservoir with fluid (2 liters)
• Lube new globes o-rings with fresh AHC fluid and place new globes near each wheel
• Unscrew old globes
• Screw on new globe and tighten (40 ft/lb?)
• Start engine. AHC will recharge.
• Change AHC to N
• Level should be above max
• Engine Off
• Bleed corners until no bubbles (one to three ounces)
• Can bleed Accumulator if wanted
• Start engine again and watch AHC recharge.
• Confirm fluid level is good. (If level is a little above max, you’re ok)
• Done

I used this wrench to remove and tighten the globes, it worked really well. No rounding or slipping.
BGS 1774 | Fan Hub Wrench | for Ford, Opel, GM | 36 mm - $32.72 - ships from the UK.

 

[IndroCruise]

I just completed replacing all 4 globes. Got my globes from Impex. Here are the steps to replace them based on the @PADDO's method shared in this thread earlier here. Sharing as it might help others. Apologies if this is redundant but I couldn't find a clear step by step.

• Engine On
• Drop to L
• Engine Off
• Bleed all 5 bleeders to where fluid stops flowing (about 1 liter). Truck will be on bump stomps
• Close all bleeders
• Suck all fluid out of reservoir with baster or something
• FILL reservoir with fluid (2 liters)
• Lube new globes o-rings with fresh AHC fluid and place new globes near each wheel
• Unscrew old globes
• Screw on new globe and tighten (40 ft/lb?)
• Start engine. AHC will recharge.
• Change AHC to N
• Level should be above max
• Engine Off
• Bleed corners until no bubbles (one to three ounces)
• Can bleed Accumulator if wanted
• Start engine again and watch AHC recharge.
• Confirm fluid level is good. (If level is a little above max, you’re ok)
• Done

I used this wrench to remove and tighten the globes, it worked really well. No rounding or slipping.
BGS 1774 | Fan Hub Wrench | for Ford, Opel, GM | 36 mm - $32.72 - ships from the UK.

Great summary! Always good to see a successful outcome well-described!

See also detailed procedures provided previously by @LndXrsr and @suprarx7nut:

“The ABCs of AHC - How to Measure, Flush, and Adjust all in one place” – thread with step-by-step guidance prepared by @LndXrsr:

The ABCs of AHC - How to Measure, Flush, and Adjust all in one place - https://forum.ih8mud.com/threads/the-abcs-of-ahc-how-to-measure-flush-and-adjust-all-in-one-place.1211999/

and

“Video and Cheat Sheet: AHC – Easy as 1 - 2- 3” – excellent video and summary sheet prepared by @suprarx7nut:

AHC Basics for dummies Video re CrossLeveling, Height Sensor adjustment, TB tweaking - https://forum.ih8mud.com/threads/ahc-basics-for-dummies-video-re-crossleveling-height-sensor-adjustment-tb-tweaking.1225842/#post-13383401

The process often goes smoothly. However, it is good to be aware that there have been many experiences reported in IH8MUD threads when air in the AHC/TEMS systems has been reluctant to leave, and the ride quality afterwards was very disappointing -- most often resolved eventually by multilple cycles of all of the bleeding steps to purge trapped air.

 

[rrc swb]

Great summary! Always good to see a successful outcome well-described!

See also detailed procedures provided previously by @LndXrsr and @suprarx7nut:

“The ABCs of AHC - How to Measure, Flush, and Adjust all in one place” – thread with step-by-step guidance prepared by @LndXrsr:

The ABCs of AHC - How to Measure, Flush, and Adjust all in one place - https://forum.ih8mud.com/threads/the-abcs-of-ahc-how-to-measure-flush-and-adjust-all-in-one-place.1211999/

and

“Video and Cheat Sheet: AHC – Easy as 1 - 2- 3” – excellent video and summary sheet prepared by @suprarx7nut:

AHC Basics for dummies Video re CrossLeveling, Height Sensor adjustment, TB tweaking - https://forum.ih8mud.com/threads/ahc-basics-for-dummies-video-re-crossleveling-height-sensor-adjustment-tb-tweaking.1225842/#post-13383401

The process often goes smoothly. However, it is good to be aware that there have been many experiences reported in IH8MUD threads when air in the AHC/TEMS systems has been reluctant to leave, and the ride quality afterwards was very disappointing -- most often resolved eventually by multilple cycles of all of the bleeding steps to purge trapped air.

This is crazy... I was just asking @FxFormat how to adjust the leveling.

The DS rear on my truck is lower by 1/2".

Thanks for the information.

 

[IndroCruise]

The DS rear on my truck is lower by 1/2".

Getting into the fine detail .....

Usually in the IH8MUD Forum and other forums we talk about hub-to-fender ‘operating heights’ being the same Right and Left: Front 19.75 inches; Rear 20.50 inches; on a stock vehicle (not lifted or lowered) -- and like all AHC-related measurements, must be done on level surface, no people or moveable load in the vehicle, fuel full, steering straight ahead.

These are not Factory Service Manual (FSM) numbers but they are good proven practical approximations for most purposes. They are independent of overall wheel/tyre diameter (because that may change the vehicle height relative to the ground but does not change the position of the hub relative to the chassis or body).

There is a limitation to these approximations: It is important that wheel/tyre diameter be the same all round, obviously meaning same type but also meaning similar wear and similar tyre pressures all round. Otherwise a lesser overall diameter or a soft tyre will try to bring the chassis closer to the ground at that point. Theoretically, if everything was perfect and the chassis was completely true with all relevant points in the same plane, then if the DS Rear corner was lower, then it would mean that the diagonally opposite corner (PS Front) would be higher.

Good as they are LC100/LX470 vehicles are not quite perfect – especially after 14 to 22 years of age and few hundred thousand miles or kilometres. Add wear and tear in the mechanical suspension parts and bushes etc supporting the vehicle, minor differences in tyres, some differences (within tolerances) way back when the chassis was manufactured, maybe a little bit of chassis twist accumulated over the life of the vehicle, and altogether it may mean that even if the front seems perfectly correct, then a measurable difference may be seen at the rear.

Half-inch difference does seem a bit much at the Rear – although for comparison I note that that FSM specification for front cross-level is +/- 10 millimetres (0.39 inches) – see attachment.

When the Front of my vehicle is cross-levelled as best I can make it, I usually see around one-eighth inch to one-quarter inch difference across the Rear, especially when my always-in-a-rush measurements by eye and tape-measure may not be any more accurate than that anyway!

The point of the story? Check the basics mentioned above, correct if necessary, otherwise live with it.

If you are interested in the FSM details and method for measuring vehicle heights for LC100/LX470 (both the same under the skin for AHC versions), check out the information at this link:

https://lc100e.github.io/manual/
At the Index Panel on the left hand side of the opening page, follow this sequence of tabs:
Repair Manual > SUSPENSION AND AXLE > FRONT WHEEL ALIGNMENT (Independent Front Axle> INSPECTION –
check the several entries relevant to the model year.

 

[rrc swb]

Getting into the fine detail .....

Usually in the IH8MUD Forum and other forums we talk about hub-to-fender ‘operating heights’ being the same Right and Left: Front 19.75 inches; Rear 20.50 inches; on a stock vehicle (not lifted or lowered) -- and like all AHC-related measurements, must be done on level surface, no people or moveable load in the vehicle, fuel full, steering straight ahead.

These are not Factory Service Manual (FSM) numbers but they are good proven practical approximations for most purposes. They are independent of overall wheel/tyre diameter (because that may change the vehicle height relative to the ground but does not change the position of the hub relative to the chassis or body).

There is a limitation to these approximations: It is important that wheel/tyre diameter be the same all round, obviously meaning same type but also meaning similar wear and similar tyre pressures all round. Otherwise a lesser overall diameter or a soft tyre will try to bring the chassis closer to the ground at that point. Theoretically, if everything was perfect and the chassis was completely true with all relevant points in the same plane, then if the DS Rear corner was lower, then it would mean that the diagonally opposite corner (PS Front) would be higher.

Good as they are LC100/LX470 vehicles are not quite perfect – especially after 14 to 22 years of age and few hundred thousand miles or kilometres. Add wear and tear in the mechanical suspension parts and bushes etc supporting the vehicle, minor differences in tyres, some differences (within tolerances) way back when the chassis was manufactured, maybe a little bit of chassis twist accumulated over the life of the vehicle, and altogether it may mean that even if the front seems perfectly correct, then a measurable difference may be seen at the rear.

Half-inch difference does seem a bit much at the Rear – although for comparison I note that that FSM specification for front cross-level is +/- 10 millimetres (0.39 inches) – see attachment.

When the Front of my vehicle is cross-levelled as best I can make it, I usually see around one-eighth inch to one-quarter inch difference across the Rear, especially when my always-in-a-rush measurements by eye and tape-measure may not be any more accurate than that anyway!

The point of the story? Check the basics mentioned above, correct if necessary, otherwise live with it.

If you are interested in the FSM details and method for measuring vehicle heights for LC100/LX470 (both the same under the skin for AHC versions), check out the information at this link:

https://lc100e.github.io/manual/
At the Index Panel on the left hand side of the opening page, follow this sequence of tabs:
Repair Manual > SUSPENSION AND AXLE > FRONT WHEEL ALIGNMENT (Independent Front Axle> INSPECTION –
check the several entries relevant to the model year.

should have said... the difference is in the rear. The 1/2" difference is from DS to PS in the rear.

I'm not too concerned between the front vs the rear.

The DS sag is very noticeable in my opinion.

Maybe I'll just have to get used to it. Like with the Rovers. The DS was always higher.

 

[IndroCruise]

should have said... the difference is in the rear. The 1/2" difference is from DS to PS in the rear.

I'm not too concerned between the front vs the rear.

The DS sag is very noticeable in my opinion.

Maybe I'll just have to get used to it. Like with the Rovers. The DS was always higher.

Apologies-- I have not been clear. I was attempting to explain the causes of the effect at the Rear, DS to PS, and the relationship to the Front. These things don't occur in isolation

 

[rrc swb]

Apologies-- I have not been clear. I was attempting to explain the causes of the effect at the Rear, DS to PS, and the relationship to the Front. These things don't occur in isolation

No need to apologize it was a great explanation.

 

[NorCalFJ100]

I just completed replacing all 4 globes. Got my globes from Impex. Here are the steps to replace them based on the @PADDO's method shared in this thread earlier here. Sharing as it might help others. Apologies if this is redundant but I couldn't find a clear step by step.

• Engine On
• Drop to L
• Engine Off
• Bleed all 5 bleeders to where fluid stops flowing (about 1 liter). Truck will be on bump stomps
• Close all bleeders
• Suck all fluid out of reservoir with baster or something
• FILL reservoir with fluid (2 liters)
• Lube new globes o-rings with fresh AHC fluid and place new globes near each wheel
• Unscrew old globes
• Screw on new globe and tighten (40 ft/lb?)
• Start engine. AHC will recharge.
• Change AHC to N
• Level should be above max
• Engine Off
• Bleed corners until no bubbles (one to three ounces)
• Can bleed Accumulator if wanted
• Start engine again and watch AHC recharge.
• Confirm fluid level is good. (If level is a little above max, you’re ok)
• Done

I used this wrench to remove and tighten the globes, it worked really well. No rounding or slipping.
BGS 1774 | Fan Hub Wrench | for Ford, Opel, GM | 36 mm - $32.72 - ships from the UK.

If I am only changing the rears, do I still need to bleed all 5? Just curious. My rears are in really bad shape and I need to change them in a hurry before work. Truck rear bounces so much its not even comfortable to drive...

 

[Moderator]

If I am only changing the rears, do I still need to bleed all 5? Just curious. My rears are in really bad shape and I need to change them in a hurry before work. Truck rear bounces so much its not even comfortable to drive...

If you are only changing the rear globes I would only bleed those 2.

 

[suprarx7nut]

If I am only changing the rears, do I still need to bleed all 5? Just curious. My rears are in really bad shape and I need to change them in a hurry before work. Truck rear bounces so much its not even comfortable to drive...

You can always bleed again later. Totally flat globes will be worse than a pretty gassy fluid mixture so I would go for it. Bleeding out the fronts and accumulator takes only a few more minutes - assuming you don't somehow run the reservoir dry or leave a bleeder open and suck in a ton of new air.

 

[IndroCruise]

You can always bleed again later. Totally flat globes will be worse than a pretty gassy fluid mixture so I would go for it. Bleeding out the fronts and accumulator takes only a few more minutes - assuming you don't somehow run the reservoir dry or leave a bleeder open and suck in a ton of new air.

@NorCalFJ100: I agree with @suprarx7nut. Do what you can while you can in the time available. Obviously be super-careful to minimise the opportunity for air to enter the system while you have it open. Inevitably, you are adding a volume of air from the open side of the new 'globe' when it is fitted to the system -- plus any air which may accidentally be drawn into the system.

The pictures below might help. If you trace the fluid pathways in the pics, it will be seen that air CAN move into the system if you are unlucky or in the event of bleeding mistakes.

If this happens, it is no big deal -- but it will mean more bleeding, sometimes a lot more. Suggest bleeding all five points (including the Height Control Accumulator) as soon as time allows -- and by the way, it need only add minutes to the job in the first place -- but take the time to proceed very carefully.

As you may know, when the vehicle is stationary (or being driven straight ahead) the Left Front and Right Front parts of the AHC system are hydraulically connected (because within the Control Valve Assembly, the Front Gate Valve is open in this condition) and the AHC pressures are equalised at Left and Right. Ditto at the Rear. Some Owners hold the view that given this connection, bleeding on one side or the other should be sufficient -- and often that seems to work. However, it is a courageous assumption because the location of bubbles or frothy fluid or fluid in which air is dissolved cannot actually be seen.

There is no similar direct connection between the Front and Rear parts of the AHC system. However, as can be seen in the diagrams below, the action of raising or lowering the vehicle, or suspension movement, can allow bubbles or frothy fluid or fluid in which air is dissolved to move towards the Height Control Accumulator. Once there has been ingress into the Accumulator of bubbles or frothy fluid or fluid in which air is dissolved, then the affected fluid can be sent by the Accumulator to all four branches of the AHC system. It may then lodge in various places, notably in the bottom portions of the Shock Absorbers from which it may be reluctant to move, because the Shock Absorbers are never fully flushed.

When something goes wrong during the bleeding effort and the above situation arises, then further very persistent, repetitive efforts at bleeding are necessary. See for example the experiences reported at this long thread

AHC Inop after fluid change 2007 lx C1751 and C1762

HELP!!! I just did the PADDO method of AHC fluid change today while wrapping up baselining a new to me 07 lx. 160k no documented AHC maintenance. Things went more or less fine but now AHC is inoperable!!! I turned the truck on the first time after the left side blead and it took about 2 min or...

forum.ih8mud.com

As a side note, it is a good idea to replace the AHC Fluid if it has not been done recently -- and repeat this periodically (USA Owner's Manual suggests replace AHC Fluid every 6 years or 60,000 miles -- see for example Page 12 and Page 24 of "Scheduled Maintenance Guide" at 2007 Toyota Land Cruiser Owners Manual and Warranty - Toyota Owners - https://www.toyota.com/owners/resources/warranty-owners-manuals.land-cruiser.2007 -- but personal view -- a more careful approach would be to halve these intervals).

The mentioned diagrams follow .....

Pic below shows fluid flow when AHC system is RAISING the vehicle -- when directed by console switch to "N" or HI" and ECU during vehicle operation, solenoid valve at Height Control Accumulator opens and Accumulator discharges fluid and pressure. AHC Pump may assist the raise in some circumstances after Accumulator has discharged, such as when driving. AHC Pump re-charges Height Control Accumulator after raise completes (green dashboard light stops blinking). FSM says re-charge of system in new stock vehicle takes 15 seconds. Strongly recommend allow 60 seconds after blinking stops for AHC Pump to recharge, to be sure of overcoming effects of age, wear and tear, weight of vehicle etc. Always a good idea to time and keep historical records of timing of both 'raise' and 'lower' movements, as times can be a symptom of other problems.

Pic below shows fluid flow when AHC system is LOWERING the vehicle -- solenoid valve at Height Control Accumulator remains closed. Neither the Accumulator nor the AHC Pump participates. When directed by console switch and ECU during vehicle operation, Levelling Valves in the Control Valve Assembly open and allow AHC Fluid to return through the system to the AHC Tank under pressure from the weight of the vehicle. In operation, vehicle lowers to "LO" height. When bleeding vehicle lowers to bump stops as fluid escapes from the system. Always a good idea to time and keep historical records of timing of both 'raise' and 'lower' movements, as times can be a symptom of other problems.

Bleeder Screw Valve is located next to pipe to/from Shock Absorber:

 

[matador454]

Trying to replace ahc globes and successfully changed one but none of the others are budging.

I have no pb blaster on me and no way to move the car (at friends house right now too). Given the other globes haven’t budged, it would suck to have to start it up with only one globe changed but is that possible? So screwed IMO

I have a 36mm wrench recommended on MUD and a strap wrench which I can’t seem to figure out

 

[BigGreenLX]

Trying to replace ahc globes and successfully changed one but none of the others are budging.

I have no pb blaster on me and no way to move the car (at friends house right now too). Given the other globes haven’t budged, it would suck to have to start it up with only one globe changed but is that possible? So screwed IMO

I have a 36mm wrench recommended on MUD and a strap wrench which I can’t seem to figure out

Only thing I'd consider trying is get a chisel and hammer. Some have been able to hit on the surface where the wrench goes and most have just carefully hit on the globe. The globes are close to 1/4" thick steel so you're not going to go through it. If you can get them started and finish with the wrench or just turn it out by hand

 

[matador454]

Only thing I'd consider trying is get a chisel and hammer. Some have been able to hit on the surface where the wrench goes and most have just carefully hit on the globe. The globes are close to 1/4" thick steel so you're not going to go through it. If you can get them started and finish with the wrench or just turn it out by hand

This was the ticket. How this isn’t the standard recommended removal procedure is beyond me

 

[BigGreenLX]

This was the ticket. How this isn’t the standard recommended removal procedure is beyond me

Good deal yeah its funny how everyone's results vary. Glad it worked out