AHC Fluid Change How To -- Need Input (5 Viewers)
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^ excellent, have you got your Techstream up and running to dial in your neutral pressures? Its very safe to say that if your torsion bars haven't been adjusted in a while (or ever) and coils are tired originals then your pressures will be much higher than the factory settings - to the detriment of your damping and overall ride quality.
I happen to work at a Lexus dealership in the sales department and did the work at our shop on a Sunday. After the work I hooked up a techstream computer to the car and got an abnormal pump pressure code C1762 along with the attached AHC Live readings which made me nervous as there was no reading for front pressure sensor as well as accumulator pressure. I was in a hurry so I went about my day but I intend to hook the car back up to the techstream to get some new readings. In doing some additional research I saw that to "refresh" the reading, you could put the vehicle in the "L" setting and bring back up to "N", then look at the AHC live screen. I was hoping to try that then see what the readings are. The system seems to be working properly as it did before the fluid change. 9 notches of movement from "L" to "H". its an '03 with 72,000 miles.
Will update once I have new readings.. this is what I have now.
Will update once I have new readings.. this is what I have now.
C1762 is a very common fault code, often as a result of some inconsequential transient hiccup. It could be ages old too. Clear it (the little engine with eraser symbol) and think about investigating if it returns. The one pressure sensor reads the pump output as the leveling valves and accumulator charging valves close - it's the leveling valves that actuate when you raise or lower - so the pressure sensor is working. I'd clear the dtc and redo and expect things to read normally. Nothing wrong with cycling between L to N back to L to N to check the pressures.
So I hooked up the truck to the techstream last night and Im glad to report that the code was gone. Yesssss!! The pressures do seem a bit high so I guess the next step toward will be to crank the font torsion bars to get the pressure inline with he factory specs.. The truck had a front brush guard installed by the previous owner which seems pretty stout and heavy. I have not yet decided if I am going to keep i or get rid of it but I suspect that its weight is adding some additional pressure to the front end. Here is a shot of the readings from yesterday. If anyone has any feedback I would love o hear it. What do you guys think of he brushguard. yay or nay...
we have the same exact color LX! what tires are those, and how is the road noise? personally not a fan of the bolt on brush guards that leave the stock bumper in place. granted, you are in NYC, so it might prevent people scraping your bumper if they park in front of you on the street.
Pressures at 8.7/7.4 are rather high. Get them down around 6.9/6.0 MPa and assuming your 4x damper accumulator globes are still healthy your damping and ride quality will be much better. Standard approach: check and adjust cross level; check and adjust front/rear heights; install coil spacers w new coils if required (likely); adjust torsion bars for optimum damping which should be around 6.7-6.9 MPa front. Well covered in the "definitive list of AHC maintenance items" thread. Start reading at the end and work backwards if you like.
The tires are 285/65 R18 BFG all terrain KO2s. I had a set on my old jeep and loved them. They look aggressive but are relatively quiet on the road. They are load range E so a bit stiffer then the stock rubber but it's a trade off I was willing to accept.
I think I will keep the brush guard for the time being but I don't love it.
I am going to crank up my TBs sometime this week and hopefully get my pressures closer to spec and will report back.
I've got to the do the same. Just did the AHC flush this evening and need to drop front pressure by about 1Mpa-g
Nothing to worry about. One can is sufficient for a good exchange and bleed, particularly if you're comfortable with working on hydraulic systems and can do it efficiently. For a lot of guys here though this is all new to them and in that case it's better to have more fluid (2 cans) on hand than being left short in the middle of the process; or if it's a first time ever fluid change then you'll benefit from a follow up bleeding to establish a good baseline. The trick is to not drain more than you can replace 
An opened second can be resealed pretty well and stored for later use.
Edited to include:
Here's my version of a quick and easy 1 can AHC fluid exchange/bleed. Following this process is less likely to get you into trouble by reducing the risk of accidentally bleeding too much fluid thereby allowing air to be drawn into your system.
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, do not restart until step 8. 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 (12 in long cylinder on DS outer frame rail, between front and rear damper assemblies) 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 and accidentally draw air into the pump/system.
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 by associating approximate quantities to the height accumulator and front/rear hydraulic circuits. Hopefully this guidance falls between the very brief FSM directions and other available AHC bleeding procedures that may appear complex and daunting to some.
An opened second can be resealed pretty well and stored for later use.Edited to include:
Here's my version of a quick and easy 1 can AHC fluid exchange/bleed. Following this process is less likely to get you into trouble by reducing the risk of accidentally bleeding too much fluid thereby allowing air to be drawn into your system.
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, do not restart until step 8. 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 (12 in long cylinder on DS outer frame rail, between front and rear damper assemblies) 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 and accidentally draw air into the pump/system.
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 by associating approximate quantities to the height accumulator and front/rear hydraulic circuits. Hopefully this guidance falls between the very brief FSM directions and other available AHC bleeding procedures that may appear complex and daunting to some.
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I used less than a can when I bled my AHC system, ran each globe out until they ran clean. Seemed to do the trick, system works as designed.
I just did mine…the new AHC fluid from Toyota is pink and easy to see the transition when bleeding. My ride improvement is noticed. Im going to change out every season IMHO. Don't over tighten the bleeders as they are hard to get on off sometimes. Let the system "absorb" the new fluid when you turn on the engine. Toyota made a nice system, but it is too expensive to replace. So I understand the different opinions regarding the AHC system. My wife will drive this 100, but won't touch my locked 80.
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Reading over this AHC fluid change thread - its great information but I have a question.
My AHC was serviced about 6 years ago and 4K miles ago.
I took a sample of the AHC fluid out of the
Reservoir and it is totally clear. I've read postings in this thread about some finding it black
and that the new fluid is pink. My AHC seems to work properly and the fluid levels in the
Reservoir between Low and High are normal.
What do assess of my situation?
My AHC was serviced about 6 years ago and 4K miles ago.
I took a sample of the AHC fluid out of the
Reservoir and it is totally clear. I've read postings in this thread about some finding it black
and that the new fluid is pink. My AHC seems to work properly and the fluid levels in the
Reservoir between Low and High are normal.
What do assess of my situation?
The fluid you get at the top of the system isn't a good representation of its condition down in the lower extremities and dead legs of the accuators as the fluid doesn't properly recirculate and there is no internal filter. At 6 years you will have some degree of nitrogen permeation so I'd replace the fluid, mainly for the fresh R&O additives and wear inhibitors, and the associated bleed then be confident you probably won't need to touch it for several more years/50k miles or whatever interval you're comfortable with.
For clarity to folks like me who are pretty new to the LX, is there a picture of the "bump stops" mentioned in the
procedure? Or is this going to be readily apparent when I get down under the vehicle?
procedure? Or is this going to be readily apparent when I get down under the vehicle?
