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

[Clunky]

I just had my AHC fluid replaced. My local indy shop quoted me over 3 hours labor. After reading many posts here that people were getting it done in an hour or less, I reached out to PADDO for advice. He provided me a step by step process that I gave to the local shop.

They ended up following his system and billed me 45 minutes of labor. They said they liked the process so much they are keeping the print out for future reference.

Thanks PADDO and MUD! I just can't say enough about PADDO's generosity, patience and willingness to share his knowledge with newbies like myself.

I'll leave it up to PADDO to bring his system to the masses.

 

[Ramathorn15]

Paddo is the go-to for anything AHC related. I assume hes probably reads the FSM on all AHC items before bed each night.

 

[uHu]

Afaik, Paddo is actually taking the info from the FSM, adding his own sound understanding, of course. So, who's this mechanic who cannot read the FSM? Maybe they also quoted for the time it would take them to find out what the AHC is, or just grabbed a "worthy" figure from thin air? Sounds more like what a dealer would serve you (in your supposed ignorance).
But anyhow: Yes, thanks to Paddo for all the work he is doing for this community.

 

[PADDO]

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.

 

[ChuckB]

Thanks PADDO and MUD! I just can't say enough about PADDO's generosity, patience and willingness to share his knowledge with newbies like myself.

I'll leave it up to PADDO to bring his system to the masses.

Yes, thanks to Paddo for all the work he is doing for this community.

Concur! Thank you for your assistance.

 

[PabloCruise]

Here's my version of a quick and easy 1 can AHC fluid exchange/bleed.

Materials required. One can of fluid (Toyota suspension fluid, AHC 08886-01805), clear pvc pipe that's a snug fit 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 at N height before starting. Clean around the reservoir cap and the spout of the AHC fluid can before opening.

1. Lower the vehicle to L and wait 30 seconds for the AHC system to settle and then turn the vehicle off. The fluid level in the reservoir will now be at its highest. Using a turkey baster or similar remove as much fluid as practical from the reservoir. This amount should equal, or be slightly over, 1 liter.
2. Pour the entire 2.5 liters of new fluid into the reservoir, filling it.
3. Now we know that the reservoir's "normal" contents is ~ 1 liter (vehicle in L when fluid level is correct at N) and we have filled it with 2.5 liters so we don't want to drain more than 1.5 liters or else we may come up short.
4. Starting at the height accumulator drain fluid, closing the bleeder as fluid flow stops which should be ~0.3 liters.
5. Move to the front LH damper and drain until the front is on the bump stops. Both sides will lower and you should drain ~0.4 liters. Again close the bleeder as fluid flow stops.
6. Move to the rear LH damper and drain until the rear is close to/on the bump stops. Both sides will lower and you should drain ~0.3 liters. Again close the bleeder as fluid flow stops.
7. Now we should have drained very close to 1 liter (0.3+0.4+0.3) leaving us about 0.5 liters additional in the reservoir.
8. Start the vehicle and raise to N. The system will refill and recharge with new fluid from the reservoir. The fluid level in the reservoir will lower 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 dampers 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 that we can't access) gets pushed out when you do the DS and take it to the bump stops as both sides are hydraulically connected.
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.

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. Hopefully it fills an information gap between the very brief FSM directions and other available AHC bleeding procedures that may appear complex and daunting to some.

Very nice , thank you!

 

[Higgin]

One quick question on this process.....At the beginning when you set the suspension to Low, remove the old fluid from the reservoir, then add the new fluid to the reservoir.....After this, do you raise the suspension back up before you start bleeding everything, or do you bleed it from the Low position? Seems like bleeding from the Neutral or High position would get a lot more fluid out, but there may not be that much that needs bled out. Everything else seems simple, just thought I'd double check on whether to bleed from L N or H before I did it. Thanks!

 

[PADDO]

One quick question on this process.....At the beginning when you set the suspension to Low, remove the old fluid from the reservoir, then add the new fluid to the reservoir.....After this, do you raise the suspension back up before you start bleeding everything, or do you bleed it from the Low position? Seems like bleeding from the Neutral or High position would get a lot more fluid out, but there may not be that much that needs bled out. Everything else seems simple, just thought I'd double check on whether to bleed from L N or H before I did it. Thanks!

Bleed it out from the L position without starting the vehicle. You want to avoid, as much as practical, diluting the new with old fluid. By bleeding the height accumulator and the front and rear actuator circuits down to the bump stops (without starting and recharging the system) you've expelled as much old fluid as you can, it's not diluted and you are in control of the volumes you're replacing and removing. Only way to get more old fluid (and air/nitrogen) out would be to disconnect and purge each shock actuator - and then it would be neither a quick or easy process

 

[tacoduck]

you doing this on jack stand? wheel ramps? thanks...

 

[PADDO]

Wheels on the ground - you want gravity to lower the vehicle and push fluid out of the four shock actuators.

 

[craaaazzy]

this was the 2nd thing i did to my "new" lx470 (heater T's were first in line) and followed paddo's easy to follow instructions (bought 3 - 1 liter containers as it seems the 2.5 liter cans are no longer available). i did drive up onto my homemade ramps to give me a little bit more room underneath (and ease my fear of getting crushed as i didn't know how low it could go).

 

[Higgin]

Bleed it out from the L position without starting the vehicle. You want to avoid, as much as practical, diluting the new with old fluid. By bleeding the height accumulator and the front and rear actuator circuits down to the bump stops (without starting and recharging the system) you've expelled as much old fluid as you can, it's not diluted and you are in control of the volumes you're replacing and removing. Only way to get more old fluid (and air/nitrogen) out would be to disconnect and purge each shock actuator - and then it would be neither a quick or easy process

Thanks a lot! That was the only thing I wasn't totally sure about. Otherwise, seems like a simple process. Guess I'll find out this weekend!

 

[tacoduck]

Wheels on the ground - you want gravity to lower the vehicle and push fluid out of the four shock actuators.

do you have to be under the truck to have access to the shock actuators?

 

[PADDO]

do you have to be under the truck to have access to the shock actuators?

For fluid change/bleeding, no. The bleed points (4 damper assemblies and 1 height accumulator) are mounted on the outer frame rails. Don't get under the vehicle to change the fluid.

 

[Higgin]

Wow, this actually WAS super easy to do per your steps! Going on a 3000+ mile trip starting next saturday, so I was glad to get this done beforehand! Took about an hour and a half. But thats just me screwing around, taking my sweet ol time. Next time, it'll be a 30 minute job for sure. Only concerning part was after everything was bled, getting back in the truck, starting it up and thinking "Please raise, please raise" as I hit the "Susp Up" button LOL. Fluid that came out when bleeding was pretty darn black. I'm debating on whether its worth it to flush it again in a month or so just to make sure all the old crap is out. Actually, come to think of it, now that the AHC fluid is in quarts, I could prob just buy another quart and use that with the 1/2 quart I still have left and do the bleed sequence without removing the fluid I just put in from the AHC reservoir. I'll probably do that after my trip. Thanks again for the steps Paddo! Made it super easy!

 

[Dannyboy lx470]

Paddo just a question.Did my bleeding all camed out nice and clean no bubbles ascept ds rear acumlator camed out with bubbles and bleed it couple of times.Once it settled tho fluid in waste bottle looked normal no bubbles like all the sides.I used Toyota hydraulic suspension fluid one can was the light gold stuff and the other was the newer red colour looking they make available now is ok to add different colours same product ? .Thanks.

 

[4WDarren]

Another big thank-you to @PADDO! Followed the write-up with no issues. Super easy. Judging by the color of the AHC fluid, this was probably the first time it was ever flushed (currently at 140k miles). Better late than never!

 

[comtal]

+ 1

Big thank you for the simple instructions. Got lucky and grabbed the last 3 bottles of fluid at the local dealer and flushed it all without issue. Excellent write up.

 

[PADDO]

@comtal thanks, glad you found it useful.

 

[MattyO]

Thanks a million. Worked like a champ!!!!