airdzi

Use best to your abilities, I prepared below below instructions to make it safe error proof procedure, this is most neglected system on your vehicle and I waited 152K miles before doing it, it was well worth it and I GOT MY SUSPENSION BACK.

When I asked my dealer I was told they do not recommend doing it unless there is a problem with the system.

You will need 1 can of Toyota AHC fluid for which there is no substitute, oil mixing large syringe from Wal-Mart, 10mm box wrench, brake bleeding kit (small plastic jar with the tube) all about $75. If you contaminated you AHC fluid with brake fluid you will need 3 cans of AHC fluid to clean and flush the system.

Test the system:
Start your vehicle and set AHC to H high setting and wait for the car to go up. You can slowly drive back and forth to speed the process. Shut down the engine, open hood and mark the fluid level on AHC reservoir. It will be low. Start the car and set the AHC to L low setting, drive slowly back and forth 20 feet or so, give it the time to lower the car down. Weight of lowered car will force fluid from actuators and accumulator to go into the AHC reservoir. Shut the engine, open hood and mark the fluid level for the low setting, it will be high. Compare the high settings mark with low setting mark with marks on the side of the AHC reservoir. Between your H and L marks you should have more than 7 fluid level marks variation on the reservoir. I had about 10, but any number above 7 means your system is in good shape. Number below 7 indicates AHC suspension system problem $$$$$.

Proceed with flush:
With engine shut down and AHC in the L settings open the AHC reservoir and use syringe with attached clear tube to empty as much old fluid out as possible. DO NOT START OR DRIVE THE CAR WITH EMPTY AHC RESERVOIR, you will draw air into the system, trigger AHC suspension low pressure sensors and lower your car flat on 4 wheels or frame stops and will require special reset procedure to get your AHC system working again. After you empty as much old fluid as possible pour the entire can of fresh fluid into the reservoir. You may top it up and may have some left in the container, that is ok, save for later.

With full AHC reservoir you can now start the car and set AHC to N normal position, fluid level will go down and fresh fluid will enter the system. That alone will help as you replaced about half of your fluid but at N your fluid should be between LOW and HIGH lines on the resvoir so you have too much in the reservoir, bleeding will empty more old fluid at the low points and allow more fresh fluid into the system. If you did everything above correctly and your system tested OK air is not the concern, you are simply removing old liquid.

BLEEDING is much easier then brakes as weight of the car will be on your side helping you. If your old fluid was not contaminated you should not try to empty all old fluid, just as much as possible to force more fresh fluid to enter the system.

BLEEDING RULES:

1. I used no jacks, just caution, keep your car on 4 wheels, plenty of access, you do not need to get under the car, just lie next to the running board.
2. You will be doing 1 wheel at the time and no more than 6oz of fluid at the time, less is safer, as if you empty actuator (will be hard to do) air can backfire thru the hose. Plastic container (brake bleeding kit from Lisle tool, car parts stores) is perfect as it is small. Small jar with clear tubing (hardware store) will do as well. Try to use clear tubing so you can see the bleeding action.
3. WATCH YOUR HEAD, if you are only doing 6oz. at the time you will not lower the car much and will be safe, still I got to warn you it is your head, once you set your 10mm wrench on the bleeding plug and hose is on the end of it all you need to watch is the tubing and the jar, do not keep your head under the running board. Take your time, do it all slow and be safe, take your time.
4. I stress again 1 wheel at the time, max 6 oz at the time, after each wheel (actuator) you will start the car and drive a bit on the level surface so self leveling system will adjust your car to other 3 wheels. It will do it by taking more fresh fluid from the reservoir and pumping it into the actuator to replace the 6 oz you take out. So after every wheel you do leveling drive you MUST check the reservoir under the hood to make sure you have enough fluid not to fall below the LOW line. Since you topped the reservoir you probably have enough to do all the wheels including the accumulation but it is your RESPONSIBILITY to check. DO NOT ALLOW RESERVOIR TO RUN OUT OF FLUID (DRY) as air will enter the system.

BLEEDING under car inspection, easy no worry.

There are four actuators - one for each wheel, under the vehicle, behind running board, corresponding with the car doors, front suspension actuators are lined up with front doors, and rear with rear doors. Each actuator has a balloon like globe at the end the size of your fist. Between the driver side actuators you will find thermos like cylinder that is your accumulator. Treat accumulator like 5th wheel, same bleeding procedure as actuators. Do it first, it is the easiest. Each has a bleeding plug zerk, which is capped with rubber cap (if you did not loose it).

Again if your fluid was never contaminated one bleeding cycle is enough. If you suspect contamination with DOT3 OR DOT4 because your tech did know any better you need to get 3 cans of AHC fluid and do it 3 times. Takes 5 minutes per wheel.

BLEEDING: ENGINE MUST BE OFF DURING BLEEDING, NOT TO TRIGGER THE PRESSURE SENSORS AND NOT TO CREATE HIGH PRESSURE MESSY SPILL, ALSO FOR YOUR SAFETY.

Do accumulator first; plug is pointing the front of the vehicle, remove rubber cap. Attach the end of the clear hose from your jar or bleeding kit on the plug, warm tubing will stretch better and easily go on. Put your wrench 10mm on the plug, MOVE YOUR HEAD AWAY and loosen the plug in the unscrew direction slowly, only takes quarter turn before you will see fluid flowing, it will be dark, gray color. As container fills up quickly tighten the plug back and stop the flow. Put rubber cap back on.

Get in the car and start the engine, drive 400 feet on level ground for suspension to level itself using fresh fluid from the reservoir. Stop the engine. Check the fluid level in the reservoir, proceed to rear driver side actuator, bleed same as above (watch your head, actuators is when car will lower itself down), drive to level the car, check level under the hood, proceed same steps rear passenger, front driver, front passenger actuators.

After 5 bleeds if your fluid in the reservoir is still above the high level and you need to empty more out repeat the process on the accumulator cylinder, it holds a lot of fluid.

Get your fluid to HIGH level as recommended per manual, YOU ARE DONE.

Go ahead drive a bit and change your car from L to H number of times with drives in between, also to cool the pump. Above will cycle the fresh fluid thru all the components, mix with any leftovers of the old fluid. It will take time so go for a long drive and watch as dampening of your ride improves. Best thing I did on my car.

Good Luck, If you are over 100K miles, do not wait. My suspension started getting very stiff around 140K miles and it drove me nuts. Above fluid change made it like new.

faast

Great write up and one question though?

Once you remove the old fluid before starting the bleeding procedure, do you fill the reservoir with the new fluid all the way to the top of the reservoir or just above the high mark?

Thanks

Linlex

Hello, I am new to the club and appreciate all the help that this post offers. I own a 2003 LX470, Recently due to many months of a bouncy type rebound in the suspension I decided to do the aftermarket shock and spring conversion. At the time I bleed the (4) actuators I was not concerned about the proper procedure to do so. After bleeding the (4) actuators I needed to discontinued the job that day due to an emergency. Later that evening after reading your post and others and remembering the dark brown color of the old fluid, I decided to try and replace the AHC fluid and see what the final result will be. This is what and how I bleed the system: I used a clear plastic tube and drained all the fluid into a bottle from the (4) actuators in this order (FL,RL,FR,RL). Until reading your post I was not aware of the accumulator and did not bleed same. The vehicle was resting on the front wheels and the rear end was supported by jack stands placed under the rear axle with rear wheels removed when system was bled. As of this post I have purchased (2) 2.5 Liters of the AHC Suspension Fluid for replacement. What I need to know is how do I proceed forward from this point to replace the suspension fluid. Thanking you in advance.

hankinid

Once I remove the old fluid from the reservoir, I add enough fresh fluid to around midpoint or an inch or so higher. I get off the floor after the accumulator and each actuator and check the level...adding more if necessary. When done, I'll top-off the reservoir up to about an inch above the "MAX" line with the system in "N".

I do not use a glass jar, just a piece of clear 1/4" tubing stuck into a milk jug. Checking the number of marks between "L" and "H" is a good overall check of the system.

I honestly see no reason to move the truck during bleeding...the system balances itself out the first time you start the truck following bleeding. No mention of driving in the factory shop manual. Interestingly, the 2001 LX manual doesn't mention the accumulator.

You'll need about a can and a half of AGC fluid to drain and flush the system. If you don't see clear fluid during the first bleeding, start the truck and bleed the same corner (or accumulator) a second time. Stop when you see clear fluid.


You cannot correctly bleed the AHC unless the truck is sitting with all 4 tires on the ground...otherwise, there's very little pressure in the system (as you bleed with engine off) to flush out the old and bring in the new fluid.

Start again with the accumulator and then the actuators, the order you used is fine. If you're not seeing clear fluid from all 5 bleeders, simply repeat.

Linlex

Thanks for the quick response. It will be a few days before I am off again to work on the LX. What should I expect after siphoning out the old fluid from the reservoir and adding the new, will the AHC Pump automatically refill the accumulator and the (4) actuators to capacity once the system start up?

hankinid

It's the same principle as bleeding the brakes. You actually refill the accumulator and actuators with the new fluid as the system drains the fluid when you open the bleeder and the truck drops. When you close the bleeder(s) and start the engine, the AHC system will pressurize the accumulator and actuators with fresh fluid. You'll know that's happening when you see the truck raise up.

Clear? If not, lemme' know.

One thing I should have mentioned was to shop around for AHC fluid...Toyota uses exactly the same PN, and normally sells it for less than Lexus.

Linlex

Gotcha loud and clear on how the AHC system refills itself on start up. About where to purchase the fluid. I learned a long time ago about the Lex and Land cruiser sharing many identical parts. Toyota price for 2.5 Liters was $44.50 and Lexus $55.00 for 1.5 Liters. Thanks again.

hankinid

2 more suggestions...

Be SURE to wear safety glasses when bleeding the AHC...pressure at HIGH with nothing in the truck can approach 800 psi.

There are VERY good deals for Toyata parts (most of your truck) via ih8mud.com user name "beno"...he runs a large Toyota parts department. A couple of online LX discount places also if beno can't get it.

Linlex

Thanks again for the info. Do you have a navigation system in your vehicle. If so have you had any issues like DVD freezes, won't eject or says DVD is not present?

hkeller

I have had this issue on my LX470 and now my LX570. Does flushing really help? Thanks,

hankinid

Hey...you're doing the same thing as an oil change...so, do oil changes really help?

Toyota recommends every 60K for normal driving, 30K for "severe" service or 2 years, whichever's first...check your owner's manual.

hkeller

Well, a flush is probably good for the extending the life of the system, as the “shocks” are an entry point for contamination, but does a flush actually improve ride quality. Has some experienced this?

hankinid

I'd say a flush keeps ride quality in a normal range...that can be verified by checking pressure on all 4 corners via TIS.