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.
