replacing AHC globes/accumulators (2 Viewers)

[Jcreme]

AHC fluid seems to be harder and harder to come by now, so I went ahead and ordered a 2.5L can. It seems to be difficult to find at dealerships, so I ordered OEM off ebay. I am going to try another flush and refill, but I'm still not sure where things went wrong the first time. I did extensive reading before doing the initial flush and globe replacement, and I have gone back through the forums again. I did find some mention (maybe by @suprarx7nut) to closing the bleeders before the fluid completely stops flowing, maybe air can enter the system back through the bleeders? I definitely kept the bleeders open until nothing else came out. I also had to leave the car overnight before putting the new globes on.

BUT after the system recharged going from L to N with the new globes and plenty of new fluid, I was able to get new clear fluid at all 5 bleeders without air bubbles. It wasn't until after I went for a test drive and cycled through all height settings that the new fluid turned milky.

I am going to hook up techstream next to check all my pressures and heights before doing any more flushing.

Can be that a globe or the accumulator failed, allowing nitrogen gas into the fluid.

After my last flush job, I kept the vehicle in high for a couple of hours to absorb gas, then lowered to L for an hour to let the gas migrate out in the reservoir. I did this for 4 or 5 cycles with good results.

I did this because the day after I flushed, the sound of the fluid coming into the reservoir as the vehicle lowered made the same hissing sound as the aerated fluid I bled out.

If you don’t have a failed component this is a near-zero-effort solution that can clean up a less than perfect bleed job.

 

[J Jamm]

Can be that a globe or the accumulator failed, allowing nitrogen gas into the fluid.

After my last flush job, I kept the vehicle in high for a couple of hours to absorb gas, then lowered to L for an hour to let the gas migrate out in the reservoir. I did this for 4 or 5 cycles with good results.

I did this because the day after I flushed, the sound of the fluid coming into the reservoir as the vehicle lowered made the same hissing sound as the aerated fluid I bled out.

If you don’t have a failed component this is a near-zero-effort solution that can clean up a less than perfect bleed job.

Thanks, I will try that. The globes are brand new OEM from Impex. I did not replace the accumulator. Until reading through your recent thread about bad fluid, I had only seen folks replacing the globes and didn't think about the accumulator going out. Hopefully when I check my pressures, the accumulator pressure will look ok. I believe it looked good when I checked it a couple months ago.

 

[suprarx7nut]

AHC fluid seems to be harder and harder to come by now, so I went ahead and ordered a 2.5L can. It seems to be difficult to find at dealerships, so I ordered OEM off ebay. I am going to try another flush and refill, but I'm still not sure where things went wrong the first time. I did extensive reading before doing the initial flush and globe replacement, and I have gone back through the forums again. I did find some mention (maybe by @suprarx7nut) to closing the bleeders before the fluid completely stops flowing, maybe air can enter the system back through the bleeders? I definitely kept the bleeders open until nothing else came out. I also had to leave the car overnight before putting the new globes on.

BUT after the system recharged going from L to N with the new globes and plenty of new fluid, I was able to get new clear fluid at all 5 bleeders without air bubbles. It wasn't until after I went for a test drive and cycled through all height settings that the new fluid turned milky.

I am going to hook up techstream next to check all my pressures and heights before doing any more flushing.

The system doesn't completely empty the shock rams during static bleed cycles (car sitting in a spot changing heights) so perhaps you're just seeing that fluid at the end of each leg get mixed better after the test drive.

 

[PhillipB]

You’re not lying about the fluid being hard to find. I ordered some from a dealership in Florida through eBay. They cancelled and refunded me. Then I ordered a can from mcgeorge. Just had it cancelled and refunded today. Bummer.

 

[ChaoticSquare]

You’re not lying about the fluid being hard to find. I ordered some from a dealership in Florida through eBay. They cancelled and refunded me. Then I ordered a can from mcgeorge. Just had it cancelled and refunded today. Bummer.

The one in Florida was a debacle. They sent me gear oil and I have the joy of going to the print the return label and mail it back. I must have gotten the last of it from McGeorge last week. Keep checking them as it comes and goes. Was out of stock when I first looked, then came back in.

 

[IndroCruise]

Wait a bit and see if it settles. There are really only two possibilities:

1. Air (many tiny bubbles) is suspended in the fluid giving it a milky look (and making for poor performance).
2. Water/Moisture has emulsified the fluid (causing it to look milky and contaminating it as well).

To follow on from @flintknapper ….

• If it is air (or nitrogen gas) in the form of fine bubbles slowly desorbing from the fluid, then that tends to rise to the top of the AHC Tank and exit to atmosphere if the vehicle is left stationary for a while (say overnight)
• If it is water/moisture (which suggests contaminated fluid), then a milky sludge may settle at the bottom of the tank.

Air (or nitrogen gas) usually is the culprit. In this case, ‘globes’ are new so hopefully nitrogen gas is unlikely – can be a problem when old ‘globes’ and failing membranes leak nitrogen into the fluid, or, possibly if nitrogen gets past the piston in a failing Height Control Accumulator or maybe even the Attenuator, but these are less likely.

If air is the problem, the source in order of likelihood, can be

• air from the newly installed ‘globes’ or when system is open while installing ‘globes’ – it is almost impossible to fill the ‘globes’ with fluid prior to installation so some air is inevitable at this step,

• air entering the system at the AHC Tank or tiny amounts of air entering while the bleeding valves are open – not really a big risk but good practice is to close the bleeder valve while the fluid is running out of the system just to be sure, or have a non-return valve in the discharge tube,

• air already in the system but may not be obvious – air can ‘hide’ in the long lines and in the unstroked part of the ‘shock absorbers’ and require persistence to shift,

• air entering the system by being drawn by the AHC Pump past the internal seals in the AHC Pump Assembly – a worn seal between the AHC Pump and its motor or tired internal o-rings within the pump are possibilities, made worse if the inlet strainer within the pump is partially blocked, starves pump of fluid, may allow pump to suck air past the seals rather than fluid from the tank – results in ongoing aeration of fluid and probably cavitation as well, which will result in a noisy and ultimately damaged pump as well as poor fluid pressure and delivery.

It is likely that the ‘milky fluid’ will turn out to mean finely disseminated tiny bubbles in the fluid visible in the AHC Tank after the driving/operating conditions described. If so, then it is inevitable that this problem fluid is fed from the AHC Tank to the Height Control Accumulator when it is re-charged after a raise “LO” to “N”, or “N” to “HI”.

Then at the next raise, the Height Control Accumulator operates and the problem fluid is sent to all four ‘globes’ and all four ‘shock absorbers’ as the vehicle raises.

In this way, the whole system can be ‘infected’ with problem fluid.

Note that the only two occasions when the solenoid valve at the front of the Height Control Accumulator is opened by the ECU is when

• the Accumulator is raising the vehicle, and,
• the Accumulator is being re-charged after a raise is completed.

The Height Control Accumulator plays no role in the normal operation of the vehicle on the road and the solenoid valve remains closed at all other times.

It is not possible to perform a ‘straight through’ flush in the AHC system in a similar way to, say, a brake system, so bleeding the AHC system can require a lot of repetitive bleeding. Basically, this aims to dilute and remove ‘infected’ fluid.

The bleeding methods set out in the FSM and in posts by @PADDO and others at IH8MUD generally work well. In these methods, bleeding is achieved with minimum new AHC Fluid.

In situations when air in the system proves difficult to shift or it is reasonable to assume that air has spread throughout the system, then my preference is full and complete repetitions of the procedure below, at least twice maybe three times.

The point of this arduous, pedantic and repetitive procedure and steps in the order given is to be quite sure that only new clean AHC Fluid is sent by the AHC Pump to the Height Control Accumulator when it is re-charged, and then, only new clean AHC Fluid is sent by the Height Control Accumulator and the AHC Pump to the ‘globes’ and ‘shock absorbers’ when the vehicle is raised.

It can be helpful to look at the diagrams of the hydraulic circuits in the third attachment when thinking through the bleeding process and making whatever adaptations may seem helpful:

1. Acquire 5 litres of genuine Toyota/Lexus AHC Fluid (probably won’t need it all but it is painful not to be able to finish the job for want of new clean AHC Fluid),

2. Personally, I am obsessive-compulsive about cleanliness of hydraulic fluid in any hydraulic system. I am disinclined to re-use fluid which has passed through the system due to concerns about dissolved or entrained air in the fluid and any other detritus the fluid may have picked up in its way through the system.

3. If fluid is packaged in 1 litre black plastic bottles (Part No. 08886-81221), decant all fluid through a funnel and a filter (for example women’s hosiery or similar) into very clean glass bottles with a cap. Suggest let the decanted fluid stand for 24 hours then observe the purity of the fluid with a strong light behind. Given the reports on IH8MUD 100 Forum and 200 Forum concerning gel in fluid, it is worthwhile to be confident of fluid quality. In Australia I buy genuine Toyota/Lexus AHC Fluid in a 2.5 litre steel drum (Part No. 08886-01805) imported from Japan and have never had the gel problem – but not sure if this package is universally available in USA or elsewhere. The same fluid is used in the AHC systems on LC100, LX470, LX570 and in the KDSS system on LC200 and in the e-KDSS system on LC300 as well as some other Toyota and Lexus vehicles -- so hopefully reliable AHC Fluid returns to the market,

4. Before proceeding, soak bleeder valves with favourite penetrating fluid of choice (multiple times days before if rust is present),

5. Start with vehicle at “LO” height,

6. Turn “OFF” engine,

7. Evacuate most fluid from AHC Tank using turkey baster or hand pump of some kind (cheap at hardware or auto stores) – but leave a little fluid at the bottom of the tank to ensure that the pump entry remains covered by fluid at all times. Set the evacuated fluid aside in a suitable clean closed container,

8. Remove and clean the strainer at the top of the AHC Tank,

9. Look inside the AHC Tank with a torch – if it is merely stained or discoloured due to age, then proceed,

10. If there is accumulated grime and debris or doubt exists, remove AHC Tank and clean with a light hydrocarbon fluid which evaporates quickly (not with detergent etc – do not want any possibility of reaction with AHC Fluid resulting in a gel or similar or any other contaminant). Rinse tank with a little AHC Fluid to remove any trace of cleaning agent and discard. Re-install AHC Tank,

11. When satisfied with condition of AHC Tank, half-fill AHC Tank with new clean AHC Fluid (need sufficient volume later to raise from “LO” to “N” without tank emptying and allowing air into the pump),

12. Start engine. If AHC Tank has been removed for cleaning, allow a little time for fluid to settle from the tank down into the pump.

13. Briefly press AHC ‘raise’ button on centre console,

14. If AHC Pump starts normally, raise vehicle to “N”.

15. If pump does not start due to removal and re-installation of AHC Tank, prime the pump by operating the “Active Test” procedure with Techstream, or using the method at paragraph 5 on Page 6 of the second attachment (using a paperclip as a connector), for ~10 seconds only, then remove paperclip, hold down AHC “ON” button for 5 seconds to engage AHC system again. Then use AHC ‘raise’ button on centre console to raise vehicle to “N”,

16. Turn engine “OFF” – IMPORTANT – in the next steps, do not want the pump to start again, do not want the Gate Valves nor the Levelling Valves in the Control Valve Assembly to operate, do not want the solenoid valve on the Height Control Accumulator to operate,

17. Bleed Rear passenger side (furthest point from pump) while observing presence of bubbles in bleed line and in fluid receptacle – should yield a lot of fluid. Rear of vehicle will sink quickly close to bump stops, so keep head and body clear. With vehicle at rest, Rear Gate Valve is open and connects RH Rear and LH Rear, so fluid will come from both Rear ‘globes’ and both Rear ‘Shock Absorbers’ as they move down through their stroke. Be aware that ‘shock absorbers’ do not ‘bottom out’ so there will be some residual fluid that cannot forced out – which is one of the reasons why repetitive bleeding is important. Record the amount of fluid collected,

18. Bleed Front passenger side (furthest point from pump) while observing presence of bubbles in bleed line and in fluid receptacle – should yield a lot of fluid. Front of vehicle will sink quickly close to bump stops, so keep head and body clear. With vehicle at rest, Front Gate Valve also is open and connects RH Front and LH Front, so fluid will come from both Front ‘globes’ and both Front ‘Shock Absorbers’. Be aware that ‘shock absorbers’ do not ‘bottom out’ so there will be some residue that cannot forced out out – which is one of the reasons why repetitive bleeding is important. Record the amount of fluid collected,

19. Bleed the Height Control Accumulator. Be wary of high fluid pressure here and crack open bleeder very gently, allow the Accumulator to empty, try to catch all fluid while observing presence of bubbles in bleed line and in fluid receptacle. The solenoid valve on the Accumulator is closed and so the Accumulator is isolated from the rest of the vehicle in this condition. The vehicle will not drop further. Record the amount of fluid collected, expecting ~300ml. The quantity is an important indicator. If it is low or nil, it means that the Accumulator has not been fully re-charged. In order of likelihood, this may be because there is air in the fluid and the pump spends its effort compressing the air rather than pushing fluid into the Accumulator, or, it may be because the pump has a partial blockage at its internal strainers and is struggling to develop sufficient pressure and flow, or, it may be that there is a fault at the solenoid valve or in the harness connecting it to the ECU so that the re-charge function is not working properly,

20. Start engine and allow vehicle to return to “N” height. This will be slow because the Height Control Accumulator is empty and the pressure and volume for the raise is being delivered only by the AHC Pump. Observe when the green AHC indicator on the dashboard has stopped blinking at “N” while listening to the pump operation. Note the time taken by the pump to re-charge the Accumulator – which is done after the raise is completed (after the green indicator is solid green). Around 15 seconds is specified for a new stock vehicle, longer for an older or very heavy vehicle. Long re-charge times may suggest an aged pump or partially blocked strainers inside the pump, or, just to confuse us all, it may be due to poor condition or conflicting adjustment of Height Control Sensors slowing down resolution by the ECU of correct height at "N",

21. Repeat the procedure as often as is required to be quite sure that there is no air remaining in the system, (or until becoming suspicious of other problems such as partial blockage of AHC Pump or malfunctioning Height Control Accumulator, etc, etc), again first dropping to “LO”, removing all fluid from the AHC Tank but leaving fluid covering the entry to the AHC pump, adding new (not recycled) fluid to the tank, raise to “N”, switch OFF engine and bleed, this time using the Rear driver’s side and Front driver’s side bleeders and again bleeding the Height Control Accumulator. Repeat as required.

The point of this arduous, pedantic and repetitive procedure in the order given is to be quite sure that only new clean AHC Fluid is sent by the AHC Pump to the Height Control Accumulator when it is re-charged, and then, only new clean AHC Fluid is sent by the Height Control Accumulator and the AHC Pump to the ‘globes’ and ‘shock absorbers’ when the vehicle is raised.

AHC Fluid ‘infected’ with air is made to exit through the bleeders – and this causes the vehicle to drop (Height Control Accumulator excepted). Some fluid may return to the AHC Tank when the vehicle drops. This fluid in the tank also is regarded as being ‘infected’ and is removed and replaced with new clean AHC Fluid before the vehicle is raised again, to ensure that the AHC Pump is drawing only new clean AHC Fluid and sending only new clean AHC Fluid on to the ‘globes’ and ‘shock absorbers’ and only new clean AHC Fluid is used to re-charge the Height Control Accumulator.

IH8MUD contains many reports of bleeding frustrations. It is often insufficient to bleed only a little fluid, hoping that ‘no bubbles’ means that all is good, then finding that this is not the complete picture after all. If aeration is widespread and arrives back at the AHC Tank, then it is important to push new clean air-free AHC Fluid right through the system and repeat this until reasonably confident of the AHC Fluid purity throughout the system. There can be a variety of ways of doing this but the objective is the same -- confidence in AHC Fluid purity throughout the system.

 

[donj51]

My professional background is wind generation. Depending on the generator platform, almost all have hydraulics from a “simple” system for the high speed brake to complex hydraulics that are in blade pitch hydraulics. There are some systems that the contamination from a human hair can block various ports.

The accumulators I have experienced are manufactured to have their nitrogen (N2) checked at least annually and almost all of the replacement accumulators are designed so that the accumulator bladders can be removed/replaced to keep parts cost down and have them recharged in the shop environment. Hydraulic fluid is sent to the lab to see how the system is operating.

I am sure there are accumulators (globes) that are available in this design and are “plug-n-play” for replacement on the AHC systems and this can assist in troubleshooting and stop the shotgun approach of replacing components that are still in manufacturing tolerances.

Without a port on the N2 side, I have no idea how the pressure can be checked, and maintained to prevent a bladder failure.

My question is do any of the replacement accumulators have a port to check the N2?

 

[xplore]

My professional background is wind generation. Depending on the generator platform, almost all have hydraulics from a “simple” system for the high speed brake to complex hydraulics that are in blade pitch hydraulics. There are some systems that the contamination from a human hair can block various ports.

The accumulators I have experienced are manufactured to have their nitrogen (N2) checked at least annually and almost all of the replacement accumulators are designed so that the accumulator bladders can be removed/replaced to keep parts cost down and have them recharged in the shop environment. Hydraulic fluid is sent to the lab to see how the system is operating.

I am sure there are accumulators (globes) that are available in this design and are “plug-n-play” for replacement on the AHC systems and this can assist in troubleshooting and stop the shotgun approach of replacing components that are still in manufacturing tolerances.

Without a port on the N2 side, I have no idea how the pressure can be checked, and maintained to prevent a bladder failure.

My question is do any of the replacement accumulators have a port to check the N2?

The OEM globes don't have a pressure port to check the nitrogen pressure, and I haven't seen any aftermarket ones that do either. This would be a great feature to have in order to troubleshoot the individual globes rather than just depending on the graduations on the reservoir which only gives a very generalized glimpse of the system health.

There were aftermarket globes floating around on the market, but I heard horror stories of early failures. They were probably just cheaply made Chinese copies. It would be nice if another manufacturer would step up to offer a quality aftermarket option with some of the features you mentioned.

 

[IndroCruise]

My professional background is wind generation. Depending on the generator platform, almost all have hydraulics from a “simple” system for the high speed brake to complex hydraulics that are in blade pitch hydraulics. There are some systems that the contamination from a human hair can block various ports.

The accumulators I have experienced are manufactured to have their nitrogen (N2) checked at least annually and almost all of the replacement accumulators are designed so that the accumulator bladders can be removed/replaced to keep parts cost down and have them recharged in the shop environment. Hydraulic fluid is sent to the lab to see how the system is operating.

I am sure there are accumulators (globes) that are available in this design and are “plug-n-play” for replacement on the AHC systems and this can assist in troubleshooting and stop the shotgun approach of replacing components that are still in manufacturing tolerances.

Without a port on the N2 side, I have no idea how the pressure can be checked, and maintained to prevent a bladder failure.

My question is do any of the replacement accumulators have a port to check the N2?

My background involved small and large scale underground and surface mining equipment hydraulics and so I also note that by comparison the hydraulic-nitrogen part of the AHC/TEMS suspension system on LC100/LX470 vehicles is straightforward. From your description, the design also is very basic compared to the systems described for blade control on wind turbines.

That said, over its design life of now around 25 years, AHC/TEMS has proven to be fit-for-purpose and very robust -- even better if not neglected and if the fundamentally basic fluid change is done at least every 6 years / 60,000 miles as recommended in US Toyota/Lexus Owners Manuals (5 years / 100,000 kilometres in Australia) and if periodic AHC fluid pressure checks are carried out. (Personal opinion: these maintenance actions should take place at least twice as often for improved system longevity – purists would say even more often. There are plenty of tiny orifices in the AHC Pump and more particularly in the Control Valve Assembly and the Damping Force Control Actuators which can be intolerant of poor hydraulic hygiene).

Front torsion bar adjustment and rear spring amendments then can be made to counter inevitably rising and ultimately excessive AHC fluid pressures which otherwise result in loss of damping performance and overloading of seals and valves.

However, the AHC fluid pressures by themselves tell nothing about the condition of the ‘globes’. At correct AHC pressures, observing difference in graduations on the AHC Tank between “LO” height and “HI” height is meant to provide a rough-and-ready indication of the reduction over time of the AHC Fluid displaced by the four ‘globes’ acting together. By inference (not directly) this is meant to indicate the state of the steadily declining nitrogen charges behind the membranes for the group of four ‘globes’.

This of course tells nothing about the state of each individual ‘globe’.

The intended inference is that 14 graduations means ‘as new’, and Toyota/Lexus advise in their Factory Service Manual (FSM) that a volume decline to 7 graduations is interpreted as insufficient overall ‘globe’ nitrogen pressure remaining for effective as-designed damping (through the variable valve settings in the Damping Force Control Actuators) and also means that some of the as-designed ‘gas spring’ performance also is lost – so FSM recommends replacement of ‘globes’ as a set.

Toyota/Lexus choose to reveal nothing about the ‘spring rates’ of the mechanical springs nor the ‘spring rates’ of the ‘gas springs’ (meaning the ‘globes’) nor the damping rates achieved by the Damping Force Control Actuators at any of the 16 damping steps available, although at least some of these things probably could be inferred experimentally.

In this way, Toyota/Lexus (and their suppliers such as KBR, AISIN and others) have protected their design and the certified road performance of stock vehicles ex factory.

Nevertheless, it cannot be beyond the ken of man to observe, experiment and model suspension dynamics and come up with safe aftermarket solutions as you suggest.

From time to time various efforts are reported on various forums and elsewhere, usually involving fitting a valve at the factory fill point of Toyota/Lexus ‘globes’ or adaptations of similar Citroen ‘globes’.

Use of off-the-shelf accumulators with the appropriate specifications, dynamic characteristics and geometry on a ‘plug and play’ basis as AHC/TEMS ‘globes’ either are not reported, or are a well kept secret which I have yet to discover!

Maybe this specialised market is just not big enough to justify the effort. Meanwhile USD600 to USD700 for a set of four replacement OEM ‘globes’, roughly every 10 years from say IMPEX or Partsouq does not seem too great an impost.

Some pictures are added below to stimulate the discussion. Comments, correction, critique are all welcome.

 

[J Jamm]

@IndroCruise Thanks for all the detailed info and for taking the time to respond.

I did some more troubleshooting tonight, and I suspect that I introduced a s*** ton of air into the system when I bled the accumulator. I made the mistake of bleeding as much as I could until it was dry, instead of stopping when there was still a solid stream of fluid. I also used 3/16" ID poly tubing that would not fit over the bleeder. I did not realize that was essential to keep air from entering. I found some 3/16" ID latex tubing that was a much better fit. I also made sure that the exit end of tubing in the bottle was kept under fluid, so that air could not come back up that way. I did the following tonight.

1. Let the vehicle sit at H and then at L for a few hours during the day after @Jcreme 's suggestion.
2. Checked pressures and heights with TS as it sat. FR -0.09", FL -0.04", RR -0.01", Front 8.4 Mpa, Rear 7.2 Mpa, Accumulator 0.0 Mpa (possibly from air in accumulator? my accumulator pressure was 10.7 before I flushed the system and changed the globes), 11 Graduations (it was 7 with the old globes)
3. Bled accumulator, bled steel hose below base of reservoir, and added fluid. Bleeding the steel hose was a recommendation by some to search for air, but I didn't notice any there. I have used just under 3L and my reservoir height is just above the minimum line.
4. Rechecked pressures and heights with TS. FR -0.10", FL -0.07", RR -0.02", Front 8.4 Mpa, Rear 7.2 Mpa, Accumulator 10.7 Mpa (removed air from accum?)
5. Adjusted torsion bars, once I finally found the adjustment points.... These were a bugger. I had to use a 24" breaker bar.
6. Rechecked pressures and heights with TS. FR -0.04", FL -0.14", RR -0.10", Front 6.9 Mpa, Rear 2.8 Mpa, Accumulator 0.0 Mpa (air moved back into accum and rear?)

I had to stop here for the night. I got my front back in spec. Rear looked out of spec and probably needs new springs. I'm not sure what happened to the rear and accumulator pressure at the last check, but possibly more air moving around? I also wonder if the rear and accumulator pressures will return back to 7.2 and 10.7 after I drive around some and cycle thru the heights. I also need to recheck the grads in the reservoir. Hopefully it will be closer to 14 with the pressures closer to spec. I am waiting on more fluid to do another complete flush that I can hopefully do better the second time.

 

[suprarx7nut]

My professional background is wind generation. Depending on the generator platform, almost all have hydraulics from a “simple” system for the high speed brake to complex hydraulics that are in blade pitch hydraulics. There are some systems that the contamination from a human hair can block various ports.

The accumulators I have experienced are manufactured to have their nitrogen (N2) checked at least annually and almost all of the replacement accumulators are designed so that the accumulator bladders can be removed/replaced to keep parts cost down and have them recharged in the shop environment. Hydraulic fluid is sent to the lab to see how the system is operating.

I am sure there are accumulators (globes) that are available in this design and are “plug-n-play” for replacement on the AHC systems and this can assist in troubleshooting and stop the shotgun approach of replacing components that are still in manufacturing tolerances.

Without a port on the N2 side, I have no idea how the pressure can be checked, and maintained to prevent a bladder failure.

My question is do any of the replacement accumulators have a port to check the N2?

My background is manufacturing engineering so lots of simple and complex system maintenance and upkeep. I think @IndroCruise touched on some of this, but I didn't read his entire reply (gotta make my mud time quick these days). Anyways, I think I can appreciate your take and sum up the difference real quick.

The AHC system on these cars, unlike any sort of manufacturing or engineering environment equipment, is designed to NEVER be touched. To NEVER need more than a mechanic's laptop and a basic wrench set. To NEVER be refilled. Alternatively, the goal was to make the longest lasting sealed unit possible. That means no valve and instead a solid welded chamber.

This also speaks to a Japanese automotive mindset vs American. For decades, and perhaps even still, American cars were made to be easy to fix. Japanese cars were typically made to be reliable. You can make part XYZ easy to replace or you can work to make it so reliable it rarely needs replacement - and therefore can be shoved wherever it fits with little regard for ease of replacement.

Also consider how few Toyota/Lexus mechanics have a clue what the AHC system is and how it should be maintained repaired. They (as a generalization) can't handle (or don't want to touch) the existing system with sealed chambers. Adding more complexity to replace bladders and recharge chambers would just put it further outside their wheelhouse. Also, don't forget that labor is one of the most expensive parts of this equation. Retaining the old part skeleton, but requiring an additional hour of labor is likely a MORE expensive proposition. CV axle rebuilds are somewhat like that. You can buy a 100% new assembly for $500. Or so can buy the high-wear outer tulip for ~$150 and then pay for 2 hours of extra labor to swap the tulip out and reboot/grease. Either way you're spending the same amount at a Lexus dealer. One of the unfortunate side-effects of a high value labor market is that it's more often financially prudent to be wasteful of material things.

 

[J Jamm]

In situations when air in the system proves difficult to shift or it is reasonable to assume that air has spread throughout the system, then my preference is full and complete repetitions of the procedure below, at least twice maybe three times.

I was able to get my hands on 5L of new fluid, two 2.5L cans at an unfortunate markup, and I am going to try the flush and refill procedure that you laid out above. Hopefully to chase out any air that I introduced previously and the milky pink fluid. One of my biggest concerns about doing another flush and refill is "bad fluid" getting pushed back into the reservoir, which made we wonder if fluid can be bled from the 5 bleeders while the vehicle is in N or H. Is it a bad idea to bleed in any height other than L? My thought being that fluid is only sent back to the reservoir when lowering from H to N or N to L, bleeding from N or H seems like a way to avoid pushing fluid back to the reservoir.

I am also considering removing the reservoir, because there is a layer of foam/scum on top of the fluid that I was really not able to remove with a turkey baster last time. I am also wondering about removing the pump to see if there is buildup from the old fluid, but I know some have had problems with disassembling the pump too far and it not working once reassembled. The old fluid was 14 years and 146k miles old. It looked like a freshly poured Guinness, which would be just right in a pub setting.

 

[apdxyk]

JFYI: 2.5-litre cans are not really a US market format any more. They are very convenient though, and it's a pity we have to hunt for the 'new' 1 qt overpriced plastic bottles. After you get a hang of it, 2 bottles per vehicle is enough. I do this every 2 years when I do my brake fluid swap.

 

[danron10]

Here's something I’ve provided to others:

I've done the changeouts two ways: combined with a full bleed and fluid replacement and I've tried a "low fluid loss method". You could probably combine both methods too. Have you got your 36mm ford fan clutch wrench from auto zone and a spare can of fluid?
Method 1. Last globe changeout I did I dropped it to L, engine OFF, bleed all 5 bleeders down to the point where fluid stops flowing (total about 1 liter) so the truck is sitting on the bump stops and then sucked out the reservoir and dumped in a full can of fresh fluid as per my quick and easy 1 can method. So you've got truck on bumps, no pressure behind any globes and a full reservoir. Unscrew old and replace the new globes, you can try and put a bit of fresh fluid in the throats of each globe but it just spills out really, but do wet the O ring with fluid. There is some spec for globe tightness but I just tighten them up and give them a bit of a nudge. After all the fan clutch wrench is 13 or 14 in long so you've got plenty of leverage there. I guess I tighten them to maybe 40 ft lbs? So when you've done the four globes start her up and it will recharge everything and then raise her to N. The fluid level in the reservoir should be a bit above max. Turn her OFF and give each corner a quick bleed, just an ounce or three till there are no bubbles. Start her up again and confirm the fluid level is good, if the level is a bit over max is ok too and you're done.
The other low fluid loss way I've done it is:
Vehicle off, at N height and jacked up the front so both front wheels are off the ground. Crack a front bleeder to relieve pressure (both sides will depressurize as they are hydraulically connected) then spin off/spin on the new globe after wetting the o ring with fluid. Move over to the other side and repeat, crack the bleeder just to make sure there is no pressure but it'll be fine. Tighten the front up, drop her back on the ground and then do the back the same way, both wheels off the ground, relieve pressure and spin off/spin on the new. Keep approximate track of just how much fluid you've drained at each corner and add that much fresh back into the reservoir, plus a cup or two for bleeding each corner. You won't bleed that much out with the wheels off the ground and the shock actuators at full extension. On the ground start her up and give each corner a bleed till no bubbles. I try and keep track of how much I'm bleeding out so I don't run the risk off getting too low in the reservoir. A quick confirmation check bleed at the height accumulator is probably worth it too. Hope this helps.

I have lc200 with ahc where I just changed my globes. Read afterwards here on the forum about additional backup washers that go behind the oring, and I guess its the same om the lx470. That package didnt contain any washer and I therefore mounted the globes without them. Should I buy the washers and do the procedure again? Or do you think it will be fine only with the provided orings?

 

[J1000]

If you have fresh fluid in your system but are fighting to get that last little bit of air out use the method of parking the truck in H for 30 minutes, parking in L for 30 minutes, H for 30, L for 30. Do that a few times in a row or maybe over the course of a few days and you should notice a huge improvement. Forgot what the thread was called someone suggested that and it worked great for me.

 

[IndroCruise]

I have lc200 with ahc where I just changed my globes. Read afterwards here on the forum about additional backup washers that go behind the oring, and I guess its the same om the lx470. That package didnt contain any washer and I therefore mounted the globes without them. Should I buy the washers and do the procedure again? Or do you think it will be fine only with the provided orings?

Cannot speak for LC200/LX570 'globes' (because I have never purchased them) but I can say that when I have purchased LC100/LX470 'globes', they arrived with the back-up ring and O-ring already correctly fitted. The back-up rings and O-rings I bought separately as a precaution were unnecessary. In my case, the 'globes' out of the box looked like the pictures posted here and also below. Note that the back-up ring is dark and made of composite material different to the O-ring -- it is easily mistaken for being part of the 'globe'. If your 'globes' arrived with the O-ring already fitted, then it seems likely that the back-up rings also were in place. Unless leaks are evident from around the thread on the 'globe', it seems like unnecessary effort to remove the 'globes' to check and then re-bleed.

@grinchy might be able to comment more specifically on LC200/LX570 'globes'.

LC100/LX470 Front 'globe' showing back-up ring behind O-ring:

 

[tone33]

You’re not lying about the fluid being hard to find. I ordered some from a dealership in Florida through eBay. They cancelled and refunded me. Then I ordered a can from mcgeorge. Just had it cancelled and refunded today. Bummer.

I just ordered a big batch from Impex (along with all new globes) - worked out to about $45 per 2.5L with shipping and all.

 

[tone33]

So much info on Mud sometimes it gets lost and hard to find! But that removal tactic is mentioned on this thread starting at about post #36. Post #44 gives a more detailed description of the “technique”. Just FYI in case someone else out there in the future needs suggestions on stuck globes.

I was surprised mine came off by soaking with Seafoam Deep Creep for a few days and fan clutch wrench. They were corroded AF! Glad you got yours out.

Since I haven't seen it mentioned on this thread (or if it was someone please call it out) - The FSM procedure is to remove the globe along with the thing it attaches to (forget what it's called). It's only a few bolts, plus have to disconnect fluid lines. The whole assembly can be put in a vice and dealt with more easily than trying to futz with a rusty connection under the truck. Especially on the right (passenger) side where you have to bang the chisel upward.

 

[yj668]

Are the issue with bad AHC fluids a long term storage issue in the plastic containers?
Or are they a 2021 manufacturing specific issue?

I have about 3 plastic bottles of late 2019 datecode AHC fluids in the garage, I had a few more bottles of these working perfectly fine in the LX right now.

 

[suprarx7nut]

Are the issue with bad AHC fluids a long term storage issue in the plastic containers?
Or are they a 2021 manufacturing specific issue?

I have about 3 plastic bottles of late 2019 datecode AHC fluids in the garage, I had a few more bottles of these working perfectly fine in the LX right now.

Manufacturing issue, far as I know.