Props to PADDO's AHC fluid replacement method! (1 Viewer)

[trdcorolla]

I was in your shoes when I got my LX. I had 5 grads (needed a flashlight to get an accurate number). I flushed the system and adjusted the torsion bars since a few here gained a few grads doing that. After the flush and TB adjustment, I still only had 5 grads. It drove like it was on pogo sticks. I replaced all my globes with OEM from the bay. I also replaced the rear springs and added a 30mm spacer to get it in spec. I had to remove the temp sensor to get my rear pressure readings. Got help from the AHC guru here @PADDO

 

[95Fantasma80]

I was in your shoes when I got my LX. I had 5 grads (needed a flashlight to get an accurate number). I flushed the system and adjusted the torsion bars since a few here gained a few grads doing that. After the flush and TB adjustment, I still only had 5 grads. It drove like it was on pogo sticks. I replaced all my globes with OEM from the bay. I also replaced the rear springs and added a 30mm spacer to get it in spec. I had to remove the temp sensor to get my rear pressure readings. Got help from the AHC guru here @PADDO

everything went smooth following @PADDO method.

after making sure I'm at the max level when in normal height, doing the low to high graduation count im at about 7-8 using flashlight because its so hard to tell, thanks for tip!

That's the first flush its had since new and its a 2001 with 188k miles.

next is techstream fun which has just arrived from amazon...

 

[colinkennedy]

Thanks @PADDO so much for writing that out. I'm a few weeks into my '02 and the fluid was horrid... took it to a shop and they didn't want to do it but i couldn't stand it so got a 2.5L tin (ebay) and 1L (dealer, which cost as much as the 2.5L o.0) and just cycled through - The procedure you wrote up worked like a champ, and everything is now running near-clear and I feel much better

Thank you, again. You saved me hundreds of dollars, and gave me (and many others) the confidence to tackle this ourselves!!

 

[AFei]

While prepare for my first AHC fluid change, I saw @PADDO 's method was mentioned everyone. However, do we have a link to the "official" @PADDO 's method?

Is it this one? Props to PADDO's AHC fluid replacement method!

 

[AFei]

And, why it's not in the FAQ?

 

[BigBen97]

Did my AHC fluid following his method yesterday. Couldn’t have been simpler once I located all of the bleeders. Huge thanks for the write up!! My biggest issue was all the snow and ice on my garage floor.

Now I need to get Techstream working.

 

[PADDO]

And, why it's not in the FAQ?

Something like a pay per click account would be good

 

[neckbone]

Have to bring this back up to the front. Anyone who hasn’t changed your ahc fluid recently, this is one of the easiest things you can do.

I did it on my ‘99 a few months ago. It wasn’t driving bad, but there was a noticeable improvement in the ride quality after I did it. Probably took me 45-60 minutes to do it.

I just finished the job on my ‘05 LX. Think it took me about 30 min this time. I couldn’t find any tubing to fit this time, but one of my kids plastic bendy straws fits the valve pretty well. I had some spillage but overall not bad. Haven’t driven it so can’t speak for ride difference.

 

[2001LC]

@PADDO I'd like your opinion, perhaps you've run into this.

I'm running into more and more where the accumulator bleeder plug is frozen and rusted in. These snap off with only a mild torque on the bleeder. It's always the accumulate in my experience. So I've no doubt it from not keeping a good bleeder cap on at all times.

Anyway I've just been leaving them in and flushing around the accumulator. Not ideal, but with frequent flushing and actively use the various modes of the AHC, it seem to be fine.

But to-date my only solution to restoring (haven't done yet) is removing accumulator and drilling out bleeder. Would be hard to do on rig, but I suppose possible with small right angle drill chuck. But more difficult to be accurate and not damaging threads.

My question to you. Do you fell that welding a bolt onto the bleeder, while accumulator on the rig or off, is viable a safe solution?

The heat if made red hot will loosen frozen threads. It should then come off easily with wrench on the welded on nut. But I've some concern with glowing red hot heat on accumulator and hydraulic fluid. Concern being damage to accumulator and fire.

 

[PADDO]

@PADDO I'd like your opinion, perhaps you've run into this.

I'm running into more and more where the accumulator bleeder plug is frozen and rusted in. These snap off with only a mild torque on the bleeder. It's always the accumulate in my experience. So I've no doubt it from not keeping a good bleeder cap on at all times.

Anyway I've just been leaving them in and flushing around the accumulator. Not ideal, but with frequent flushing and actively use the various modes of the AHC, it seem to be fine.

But to-date my only solution to restoring (haven't done yet) is removing accumulator and drilling out bleeder. Would be hard to do on rig, but I suppose possible with small right angle drill chuck. But more difficult to be accurate and not damaging threads.

My question to you. Do you fell that welding a bolt onto the bleeder, while accumulator on the rig or off, is viable a safe solution?

The heat if made red hot will loosen frozen threads. It should then come off easily with wrench on the welded on nut. But I've some concern with glowing red hot heat on accumulator and hydraulic fluid. Concern being damage to accumulator and fire.

Just had a chance to look at some spare parts and noticed that on both spare height accumulators (and my fitted one) I’ve got the bleeder is internally drilled to ~2.6mm into a 5.3mm OD bleeder body stock and the bleeders for the damper assemblies are drilled to ~1.9mm for the same OD body: there’s less wall thickness for height accumulator bleeders (at least the ones I checked) hence they’ll be more prone to shearing if there’s any corrosion. One small mystery solved . In both cases the thread OD measured 6.7mm and the seat tapers appeared very similar, not identical, but I suspect a damper assembly bleeder would seat properly under pressure if used in the height accumulator and vice versa. You could probably drill, say, to 5mm without damaging the height accumulators thread. A 4mm or 5mm reverse twist drill would be my choice. Spot heating the broken stub might be OK but I definitely wouldn’t heat soak the height accumulator body as you’ve got hydraulic fluid, a solenoid and a 1000psi of nitrogen in close proximity. The less then perfect, but functional, work around would be to leave the busted height accumulator bleeder stub in place and just bleed around it by letting the accumulator discharge its fluid content during a raise cycle and turning the vehicle off before the pump starts to recharge it (then siphon off and bleed down to the bump stops) or by using Techstream utility you can activate the height accumulator multiple times and it will discharge back to tank where you can siphon off and bleed down to the bump stops. Either way you’ve discharged the old fluid out of the height accumulator.

 

[2001LC]

Thank you @PADDO. I should have said Height Accumulator.

 

[AFei]

Finally replaced the AHC fluid on my 04 LX. Thanks a billion to @PADDO !
Old fluid:

After replaced, new fluid drained from the passenger side:

 

[AFei]

So I read the AHC data by Techstream. Would anyone help to review the data and let me know my next step? From my reading I know there is something to do with the torsion bar first, but just has no experience at all. Any help is appreciated.

Reading at Hi:

Reading at Nm:

Reading at Lo:

 

[BigBen97]

AFei, did you follow the procedure properly? Those numbers look like what I had when I wasn’t doing it properly. Was 10.9/8.7 when done incorrectly, then had 7.8/6.9 when done properly (at least so I believe).

Here’s my approach now since as I understand it:
1. Check heights from wheel center to edge of fender. Adjust height sensors (mechanically) to get those within spec. The spec for that is in this thread.
2. Retest pressures then adjust torsion bars as needed to get front pressures within spec. Spec for turn to pressure change is in this thread.
3. Retest confirm front pressure is in spec and to see what needs to be done for the rear pressures. From my reading it could be spacers or new OEM springs assuming by some miracle it doesn’t drop when lowering the front pressure. From what I’ve read the rear will likely go up when lowering pressure on the front.

 

[AFei]

AFei, did you follow the procedure properly? Those numbers look like what I had when I wasn’t doing it properly. Was 10.9/8.7 when done incorrectly, then had 7.8/6.9 when done properly (at least so I believe).

Here’s my approach now since as I understand it:
1. Check heights from wheel center to edge of fender. Adjust height sensors (mechanically) to get those within spec. The spec for that is in this thread.
2. Retest pressures then adjust torsion bars as needed to get front pressures within spec. Spec for turn to pressure change is in this thread.
3. Retest confirm front pressure is in spec and to see what needs to be done for the rear pressures. From my reading it could be spacers or new OEM springs assuming by some miracle it doesn’t drop when lowering the front pressure. From what I’ve read the rear will likely go up when lowering pressure on the front.

Well the pressure was pretty unchanged before and after the AHC fluid changed.

Thanks for telling me to mechanically adjust the height sensors to get height within spec. I was thinking it's done by torsion bar adjustment. Just not quite sure how could that got changed.

So once the height is within spec, the next step is to adjust the TB to get the front pressure into spec. And the rear pressure is the last step and can only be done by new stronger spring?

 

[PADDO]

@AFei your pressure readings make no sense. Recommend a redo on flat level ground, no additional weight, nominally a full tank of fuel and just go from L to N as readings taken at H or L aren’t relevant. And please include actual height measurements front center hub to fender bottoms as this helps complete the picture of your setup and helps eliminate guessing.

 

[AFei]

@AFei your pressure readings make no sense. Recommend a redo on flat level ground, no additional weight, nominally a full tank of fuel and just go from L to N as readings taken at H or L aren’t relevant. And please include actual height measurements front center hub to fender bottoms as this helps complete the picture of your setup and helps eliminate guessing.

Hmmmm I will retry when get back home. It was tested in the garage which should be most level. Thanks!

 

[JWick]

Thanks for the perfect process and write up @PADDO ! Worked like a charm and happy to have gotten rid of this nasty AHC fluid.

 

[Eltestro]

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

Would I able to do this with no prior mechanic experience?

 

[IndroCruise]

Many thanks to PADDO, UHU and all who have gone before.

In my case – 2006 HDJ100R Toyota Landcruiser Sahara 4.2 litre turbodiesel with AHC – the flush-and-bleed followed installation of new Toyota OEM gas chambers or spheres supplied by Megazip of Singapore (Front: Toyota Part No. 49141-60010; Rear: Toyota Part No. 49151-60010). This was the first replacement after 183,216 kilometres (113,845 miles) and almost 13 years. The vehicle lives in easy suburban conditions in Brisbane Australia and only sees tough conditions on occasional trips around the country.

Before the change, the volume test showed 9 graduations on the AHC tank from “LO” to “HI”. In Australian conditions, 8 graduations appears to be the recommended minimum if I am understanding the FSM correctly. The ride still seemed reasonable but the test and age of the vehicle suggested that the gas chambers (spheres) were past their best and it was time to prepare for several long trips across Australia – probably another 10,000 to 15,000 kilometres in the next year.

Anyway, all seemed to go well with the change-out of parts and also with the flush and bleed with new light red AHC fluid (Toyota Part No. 08886-01805).

After the change, the volume test showed 14+ graduations when moving from “LO” to “HI” -- I added a bit too much new fluid, made level a bit hard to read because new light red fluid level ran across the join half way up the AHC tank!

Now I need to check pressures when I get Techstream working.

Meanwhile a question: The ride now seems a bit firmer after this work than it was before the work so I am wondering whether this is normal or whether it is signalling some other problem?

Also, I am not sensing much difference between “COMFORT” and “SPORT” settings on the TEMS switch.

Advice is welcome from anywhere in the world ….