Props to PADDO's AHC fluid replacement method! (3 Viewers)

[FxFormat]

I need help, i replaced the front left shock and everything was fine, car was raising up and down, then for some reason i decided to lift the entire truck up and crack open the bleeder by the front globe, now the car is on bumpstops and i can't get it to raise. I've bled all the corners and didn't see any bubbles, i opened the accumulator (12" long tube thingie on the driver's frame) now no fluid is coming out, even with the pump running, there's no fluid coming out. Anybody have any ideas?

I scanned it with my scanner and got code C1751 and C1762


Edit: nvm, I kept cycling the pump off and on and eventually it built pressure in the accumulator . All is good now!

 

[willyroo]

Resurrecting an older thread, however another "thanks mate" for @PADDO 's easy to follow directions.

My local Lexus dealer quoted A$500 + 2 X 2.5 litre cans ($73 each) for this, so a lot of incentive to DIY.

For us Aussies, the slight change to directions is for the final "check bleed" (Step 9). This is done on the driver's side, being the RHS of the vehicle.

Top tip - offer your 20 year old MechEng student beer for wrenching . Tip 2, a cheap 200ml fluid extractor works a treat to fully drain the main reservoir, including sludge at the bottom. We got out just over 1.1 litres of worn out AHC fluid.

There was a decent pressure release on the main accumulator - so remember to do that very slowly, however everything else went perfectly. The original globes are still in excellent condition (204,700kms or around 124,000mi), with 12 gradations prior to flush and the final result being just over the "max" line.

For Aussies that know the term "Lo-lux", here's a Lo-lex

Another reason to stick with AHC!

Oh and my apprentice suggested new caps for the globes. Lookup these parts on Amayama:

4 X 49189-60010 (plug)
4 X 49177-60010 (cap)

 

[Novalikestofly]

Edited for extra detail.

Here's a quick, easy and efficient 1 can (or 3 bottle) AHC fluid exchange/bleed procedure. By following this process you are very unlikely to get yourself into trouble by accidentally bleeding too much fluid. Furthermore, it's not at all wasteful of new fluid as you remove a considerable amount of the old fluid/gas/air and recharge the whole system with fresh fluid in just one cycle. No wasteful start/stop/bleed/start/stop...... process.

The benefits of periodically changing out the AHC/AVS systems' fluid can't be overstated as this mineral based working oil degrades with time, temperature and use. Fluid viscosity changes, anti wear, anti rust, anti foaming, anti oxidation additives deplete and the fluid picks up particulate and other contamination. Sludge forms in the pump intake chamber and nitrogen from the accumulators permeates into the system, virtually all hydraulic systems will allow air to come out of fluid solution and form bubbles with use and time. The combination of degrading fluid and entrained gases affects damping performance and ultimately can't promote the maximum service life of the system. FWIW I change out the systems fluid at half the recommended service interval, or about 30k miles/3 years.

Materials required. One can of fluid (Toyota suspension fluid, AHC 08886-01805) or three of the new 1L bottles (08886-81221), clear pvc pipe that's a snug fit (3/16 ID) on the bleeders, 10mm spanner/box wrench/crows foot and a suitable waste fluid container.

This process assumes the fluid level in the reservoir is between max and min when the vehicle is at Normal height before commencing and the 5 bleeder points aren't frozen due to corrosion. If corrosion is an issue then consider spraying a penetrating oil (PB Blaster etc) on the bleeders several times over a few days beforehand and use a good quality 6 point 10mm socket wrench. If you can't open the bleed points due to rust then an option would be to drive the AHC system down to the bump stops (lower then L and returning the maximum amount of fluid back to the reservoir for removal) in Active Test Mode and remove/replenish the fluid from the reservoir and not attempt bleeding at the 5 points. Not optimal but probably better than doing nothing. Always clean around the reservoir cap and the spout of the AHC fluid can before opening and avoid introducing any contamination into the reservoir.

This maintenance activity needs to be done with the vehicle on flatish, level ground and not on a lift or with the wheels off the ground as you need the vehicle's weight to compress the shock actuators down to the bump stops to remove the maximum amount of old fluid. Don't get under the vehicle, you access the five bleed points on the outer frame rails.

1. Lower the vehicle to LOW and wait 30 seconds for the AHC system to settle and then turn the vehicle OFF. Do not restart the engine until step 8. The fluid in the reservoir will now be at its highest level. Remove the reservoir filter screen and using a turkey baster or similar suction device remove as much of this old fluid as practical from the reservoir. The amount removed should equal, or be slightly over, 1 liter [if you were between Max and Min at N].
2. Replace the filter screen and pour the entire contents of a 2.5 liter can [or 2 1/2 x 1 liter bottles] of new fluid into the emptied reservoir. It will be very close to completely full.
3. Now we know that the reservoir's "normal" contents is ~ 1 liter (vehicle in L when fluid level is correct at N) and you have just filled it with 2.5 liters so you don't want to drain/bleed more than 1.5 liters or else you may end up with insufficient fluid on completion.
4. Starting at the height accumulator (12 inch long cylinder on DS outer frame rail, between front and rear damper assemblies) connect your drain tube, crack the bleeder and commence draining fluid, closing the bleeder as fluid flow stops. You should drain ~0.3 liters.
5. Move to the front LH damper assembly, connect tube, crack the bleeder and drain until the front has dropped down to the bump stops. Both sides of the vehicle will lower together (because they are hydraulically connected) and you should drain ~0.4 liters. Again close the bleeder as fluid flow stops.
6. Move to the rear LH damper assembly, connect tube, crack the bleeder and drain until the rear is close to/on the bump stops. Both sides will lower like the front did and you should drain ~0.3 liters. Again close the bleeder as fluid flow stops.
7. Now you should have drained very close to 1 liter (0.3+0.4+0.3 for healthy damper accumulator spheres; if you have degraded or blown spheres then you'll likely drain less fluid as there's limited/no nitrogen charge to expel the spheres fluid contents) leaving you about 0.5 liters "excess" in the reservoir.
8. Start the vehicle, let it idle for 30-60 seconds and then press the UP button to raise to NORMAL height. The whole system will refill and recharge with new fluid from the reservoir and the level in the reservoir will be drawn down to slightly over the max line if everything has gone as expected.
9. Turn the vehicle OFF and do a small, quick bleed on the PS front and rear damper assemblies just to check that there isn't any gas trapped. You don't need to remove very much at all from the PS as essentially all available fluid (there will always be a small residual in each shock actuator/damper that we can't access) is forced out when you do the DS dropping the vehicle down to the bump stops.
10. You're done, confirm that the reservoir fluid level is correct - between max and min at N height with the engine running. There is nothing wrong with leaving the level slightly over the max line.

As long as you don't drain more than 1.5 liters you can't mess up and accidentally draw air into the pump/system through the reservoir or be left short of fluid.

This approach is simpler than others, but slightly more elaborate than the FSM. It is intended to remove as much old fluid as practical in a quick and efficient manner. It doesn't waste new, fresh fluid like the drain/start/stop/drain/start etc method. Hopefully this method fills an information gap by associating approximate quantities drained to the height accumulator and the front/rear hydraulic circuits and gives people the confidence to undertake this simple yet critically important maintenance procedure.

View attachment 1770402

Just finished AHC flush but reservoir has a large amount of fluid left. Well above max line in N. How big of a problem is this and how should I remedy?

 

[IndroCruise]

Just finished AHC flush but reservoir has a large amount of fluid left. Well above max line in N. How big of a problem is this and how should I remedy?

This is not a big deal -- the MAX and MIN levels are only a guide. Just be sure that there is enough space left in the reservoir for fluid when vehicle is in LO mode, and then some, in case some problem occurs like faulty Height Control Sensors. This may send the vehicle all the way to the bump stops and send even more fluid back to the reservoir. If reservoir is really over-full, fluid could overflow and spill, especially when/if the vehicle is on extreme slopes.

Use a simple cheap hand pump or turkey baster or similar to suck fluid from reservoir until it is at safe level. A little too much fluid is better than not enough -- do not want to draw air into the system when vehicle is put in HI mode and much fluid is sent to the 'shock absorbers' to raise the vehicle, possibly emptying the reservoir if available fluid is insufficient.

When doing an AHC Fluid change, best to start by removing most of the old fluid from the reservoir at LO mode, but be aware that if the bottom of the reservoir is completely exposed, air may enter the AHC Pump below the reservoir. Then thorough bleeding of the system will be necessary to remove the air. "Active Test" also may be necessary to re-start the AHC Pump.

 

[w4lks0ftly]

Edited for extra detail.

Here's a quick, easy and efficient 1 can (or 3 bottle) AHC fluid exchange/bleed procedure. By following this process you are very unlikely to get yourself into trouble by accidentally bleeding too much fluid. Furthermore, it's not at all wasteful of new fluid as you remove a considerable amount of the old fluid/gas/air and recharge the whole system with fresh fluid in just one cycle. No wasteful start/stop/bleed/start/stop...... process.

The benefits of periodically changing out the AHC/AVS systems' fluid can't be overstated as this mineral based working oil degrades with time, temperature and use. Fluid viscosity changes, anti wear, anti rust, anti foaming, anti oxidation additives deplete and the fluid picks up particulate and other contamination. Sludge forms in the pump intake chamber and nitrogen from the accumulators permeates into the system, virtually all hydraulic systems will allow air to come out of fluid solution and form bubbles with use and time. The combination of degrading fluid and entrained gases affects damping performance and ultimately can't promote the maximum service life of the system. FWIW I change out the systems fluid at half the recommended service interval, or about 30k miles/3 years.

Materials required. One can of fluid (Toyota suspension fluid, AHC 08886-01805) or three of the new 1L bottles (08886-81221), clear pvc pipe that's a snug fit (3/16 ID) on the bleeders, 10mm spanner/box wrench/crows foot and a suitable waste fluid container.

This process assumes the fluid level in the reservoir is between max and min when the vehicle is at Normal height before commencing and the 5 bleeder points aren't frozen due to corrosion. If corrosion is an issue then consider spraying a penetrating oil (PB Blaster etc) on the bleeders several times over a few days beforehand and use a good quality 6 point 10mm socket wrench. If you can't open the bleed points due to rust then an option would be to drive the AHC system down to the bump stops (lower then L and returning the maximum amount of fluid back to the reservoir for removal) in Active Test Mode and remove/replenish the fluid from the reservoir and not attempt bleeding at the 5 points. Not optimal but probably better than doing nothing. Always clean around the reservoir cap and the spout of the AHC fluid can before opening and avoid introducing any contamination into the reservoir.

This maintenance activity needs to be done with the vehicle on flatish, level ground and not on a lift or with the wheels off the ground as you need the vehicle's weight to compress the shock actuators down to the bump stops to remove the maximum amount of old fluid. Don't get under the vehicle, you access the five bleed points on the outer frame rails.

1. Lower the vehicle to LOW and wait 30 seconds for the AHC system to settle and then turn the vehicle OFF. Do not restart the engine until step 8. The fluid in the reservoir will now be at its highest level. Remove the reservoir filter screen and using a turkey baster or similar suction device remove as much of this old fluid as practical from the reservoir. The amount removed should equal, or be slightly over, 1 liter [if you were between Max and Min at N].
2. Replace the filter screen and pour the entire contents of a 2.5 liter can [or 2 1/2 x 1 liter bottles] of new fluid into the emptied reservoir. It will be very close to completely full.
3. Now we know that the reservoir's "normal" contents is ~ 1 liter (vehicle in L when fluid level is correct at N) and you have just filled it with 2.5 liters so you don't want to drain/bleed more than 1.5 liters or else you may end up with insufficient fluid on completion.
4. Starting at the height accumulator (12 inch long cylinder on DS outer frame rail, between front and rear damper assemblies) connect your drain tube, crack the bleeder and commence draining fluid, closing the bleeder as fluid flow stops. You should drain ~0.3 liters.
5. Move to the front LH damper assembly, connect tube, crack the bleeder and drain until the front has dropped down to the bump stops. Both sides of the vehicle will lower together (because they are hydraulically connected) and you should drain ~0.4 liters. Again close the bleeder as fluid flow stops.
6. Move to the rear LH damper assembly, connect tube, crack the bleeder and drain until the rear is close to/on the bump stops. Both sides will lower like the front did and you should drain ~0.3 liters. Again close the bleeder as fluid flow stops.
7. Now you should have drained very close to 1 liter (0.3+0.4+0.3 for healthy damper accumulator spheres; if you have degraded or blown spheres then you'll likely drain less fluid as there's limited/no nitrogen charge to expel the spheres fluid contents) leaving you about 0.5 liters "excess" in the reservoir.
8. Start the vehicle, let it idle for 30-60 seconds and then press the UP button to raise to NORMAL height. The whole system will refill and recharge with new fluid from the reservoir and the level in the reservoir will be drawn down to slightly over the max line if everything has gone as expected.
9. Turn the vehicle OFF and do a small, quick bleed on the PS front and rear damper assemblies just to check that there isn't any gas trapped. You don't need to remove very much at all from the PS as essentially all available fluid (there will always be a small residual in each shock actuator/damper that we can't access) is forced out when you do the DS dropping the vehicle down to the bump stops.
10. You're done, confirm that the reservoir fluid level is correct - between max and min at N height with the engine running. There is nothing wrong with leaving the level slightly over the max line.

As long as you don't drain more than 1.5 liters you can't mess up and accidentally draw air into the pump/system through the reservoir or be left short of fluid.

This approach is simpler than others, but slightly more elaborate than the FSM. It is intended to remove as much old fluid as practical in a quick and efficient manner. It doesn't waste new, fresh fluid like the drain/start/stop/drain/start etc method. Hopefully this method fills an information gap by associating approximate quantities drained to the height accumulator and the front/rear hydraulic circuits and gives people the confidence to undertake this simple yet critically important maintenance procedure.

View attachment 1770402

I join the many before me to thank @PADDO for his incredibly clear and effective write-up of this process. Flushing the AHC went off without a hitch, and courtesy of confidence in these good directions, my 6-year-old assistant was able join in helping on a low-stress job!

 

[Kingrich33]

Big thanks to @PADDO, just did this on my ‘04 and worked like a charm. Out with the old and in with the new…

 

[NKP Garage]

Big thanks to @PADDO, just did this on my ‘04 and worked like a charm. Out with the old and in with the new…View attachment 3484390

Nice work!

 

[ronnunan]

Props to @PADDO For the step by step. I have a hiccup in my end result. I followed the direction and all seemed good until I noticed after driving around a bit (the ride was great-better than before) and coming to a stop. I went from N to L and I heard and felt some shuddering and thudding while lowering. This also occurred a couple other times while lowering from H to N and N to L.
It didn’t do it every time but it still does it when I don’t go through the heights… like if I drive a bit and come home and throw it to N after getting off the freeway it will shudder and thud. But it always finishes its cycle. Of coarse when I got home and went through all the cycles tonight it didn’t do it once.
Any ideas?

 

[terryscott621]

Another shout out to @PADDO for his procedure. Just did this today on my new to me ‘02 with 258k miles. Super easy took about 45mins. Old fluid was black and definitely needed to be changed.

 

[babybluelincoln]

I posted this on my own separate thread but thought I'd ask the question on this one to see if I can get a little more advice.

Tried to flush the AHC fluid tonight and sheared off the bleed screw to the accumulator. What are my options now? System is/was working fine, just wanted to change the fluid as it has not been done in a long time.

Do I need to replace the accumulator now? Do I try and extract what is left of the bleeder screw? If I can even get it to budge, there is fluid in the system which will come pouring out. Is there an issue running the accumulator dry? How much pressure is in the accumulator if I have to drill out or extract the sheared bleeder screw?

Read and reread the ABC's to AHC and watched several Youtube videos before getting the nerve up to do this and the first bleeder screw I touched, shears off. I did hit the bleeders with PB Blaster for a few days, when it wouldn't budge I even tried to heat it up a bit. FML,.

Any help or advice is appreciated

 

[2001LC]

Bleed around it.

Trick to flush/bleeding around height accumulator:
The height accumulator fills/pressurises, after vehicle raised. That is why, we hear the pump running, after vehicle up. Open door (turns off pump) just as vehicle has raised, to stop pump from filling accumulator. Then, flush/bleed rear & front globes.

Note on bleeders:
All 9 bleeders (4 brake, 5 AHC) must be kept capped with rubber caps. Or they rust, from inside at seat area cavity. The height accumulator, has the thinnest walled bleeder. So it bust the easiest when rusted in. If rusting allowed to go on for too long. The seat of bleeder is damaged, so may then need replacing. Even longer unchecked, and where bleeder seats may be damaged. Then the caliper or accumulator must be replaced if seal can't be made.
The height accumulator and rear calipers, are where we have the most issues.

 

[babybluelincoln]

Bleed around it.

Trick to flush/bleeding around height accumulator:
The height accumulator fills/pressurises, after vehicle raised. That is why, we hear the pump running, after vehicle up. Open door (turns off pump) just as vehicle has raised, to stop pump from filling accumulator. Then, flush/bleed rear & front globes.

Note on bleeders:
All 9 bleeders (4 brake, 5 AHC) must be kept capped with rubber caps. Or they rust, from inside at seat area cavity. The height accumulator, has the thinnest walled bleeder. So it bust the easiest when rusted in. If rusting allowed to go on for too long. The seat of bleeder is damaged, so may then need replacing. Even longer unchecked, and where bleeder seats may be damaged. Then the caliper or accumulator must be replaced if seal can't be made.
The height accumulator and rear calipers, are where we have the most issues.

Thank you for this information, I will give this a try this weekend, I'll continue to flush it when needed like this until the accumulator quits someday.

For what it is worth, the accumulator did not have a cap on it, the only one that did not. Thank you again.

 

[IndroCruise]

Thank you for this information, I will give this a try this weekend, I'll continue to flush it when needed like this until the accumulator quits someday.

For what it is worth, the accumulator did not have a cap on it, the only one that did not. Thank you again.

The workaround is well-described by @2001LC, as always..

Just to add belatedly some more information ….

The point is that the ONLY function of the Height Control Accumulator in the AHC/TEMS systems is to assist in quickly raising the vehicle when required, using the console switch. The Height Control Accumulator has no function at any other time during the operation of the vehicle.

FSM Extracts ....

So when the Height Control Accumulator bleeder valve cannot be used for bleeding, the idea is to start the bleed with the Height Control Accumulator discharged and empty of its ~300 mL of AHC Fluid. This occurs when a raise is completing and before the ECU causes the AHC Pump to recharge (refill) the empty Height Control Accumulator. Then bleeding can continue using the bleeder valves at each of the four Damping Force Control Actuators (to which the ‘globes’ are attached).

It is always important to ensure that the AHC Tank does not become so completely empty that air enters the AHC system. When this happens, air-polluted AHC Fluid arrives at the Height Control Accumulator and is then distributed throughout the system when the vehicle is next raised and the Height Control Accumulator discharges its then air-polluted AHC Fluid. Even in this accidental situation, inability to open the bleeder valve at the Height Control Accumulator is not fatal -- but it may mean that more than usual repetitions of the bleeding process are necessary to clear the air-polluted AHC Fluid from the system.

If your vehicle is a 2006 LX470 ex-Texas (?), then it is likely that the AHC system (and the underbody generally) is in good rust-free condition without damage to the pipelines and the wiring looms. If that is the case, then the benefits of the AHC/TEMS systems -- meaning whenever the vehicle is operating (1) auto-self-levelling in real time; (2) auto-damping and comfort adjustment responding to road and driving conditions in 16 steps in real time; (3) height adjustment by console selector when required -- all can be expected to remain functional and highly reliable for many more go-anywhere years -- provided that AHC/TEMS basic maintenance is followed, specifically:

• annual visual inspection of underbody condition -- looking for leaks at AHC pipe joins, rusty bleeders, missing caps, leaks at ‘shock absorbers’ (which may indicate excessive AHC pressures, can be corrected easily), condition of Height Control Sensors -- two at the Front and one at the Rear -- these are longlasting 'wear items' in a hostile environment but will not last forever and eventually will breakdown, condition of bushes at ‘shock absorbers’ and at all suspension linkages,
• annual check of Front cross-level of vehicle and adjustment if necessary using Torsion Bar adjusters,
• annual check of vehicle hub-to-fender heights at each wheel and adjustment if necessary using the Height Control Sensor Adjusters (not the Torsion Bar adjusters),
• annual (or whenever additional permanent weight is added), check and adjustment of suspension settings if necessary (meaning Front torsion bar adjustment, packers or new springs at Rear) to ensure that Front and Rear AHC pressures remain within the FSM-specfied ranges,
• with heights and pressures correct, annual check of overall condition of the four 'globes' by checking that the difference in AHC Fluid Level at the AHC Tank at LO height and HI height is better than 7 graduations (replace ‘globes’) compared to 14 graduations (when ‘globes’ are new),
• change-out of AHC Fluid Part Number 08886-01805 per Owner’s Manual each 6 years or 100,000 miles (twice as often is better for internal ‘hydraulic hygiene’) -- and use the opportunity to replace all bleeder valves AND caps (essential!) -- excellent investment for very few dollars -- see Part Numbers in pic below,
• replacement of all four ‘globes’ when approaching 7 graduations at the AHC Tank (expect 10+ years for life of OEM ‘globes’),
• review the attached illustrated “General Description” of the AHC/TEMS systems to refresh understanding of these systems,
• review the AHC/TEMS sections of the Factory Service Manual (FSM) at LC100 Factory Service Manual - https://lc100e.github.io/ pertaining to the AHC/TEMS systems -- same for LC100 where fitted and LX470,

On a young low-mileage 2006 LX470 vehicle, replacement of the Height Control Accumulator should never be necessary, even if the bleeder valve is ‘stuck’ -- just continue the workaround process.

@Moridinbg has explained his effort to overcome a stuck bleeder valve in Height Control Accumulator -- this method avoids removing the Height Control Accumulator from the LH chassis rail which can be a PITA job -- but this alternative is not for the faint-heated -- see Post #37 and Post #41 at this thread:
Fixing the AHC from hell - https://forum.ih8mud.com/threads/fixing-the-ahc-from-hell.1300130/page-2#post-15607207

Bleeder and Cap Part Numbers: