Changing out the AHC suspension fluid?

[hoser]

I've adjusted the AHC sensors on my LX to give it some lift. Now the fluid is low so I might as well flush and bleed the system instead of just adding--afterall the fluid does get pretty hot and is subject to moisture.

So, anybody know if there is a specific order to do this? Here's a diagram where you can see the "bleeder plugs" on the accumulators. Now what?

[CTapia]

Hoser,

Sorry, I don't have the answer to your question, but how about more details or a write up on how to adjust sensors for the lift?

[FinallyGotOne!]

Just another example of a routine maintenance procedures apparently missing from the TIS. I hope someone can post the procedure here!

[powderpig]

I do not have a procedure for you but the fluid is quite spendy, and toyota only reccommends it stuff for the system. 30-35 a gallon. later robbie

[hkeller]

Hey. I just did this on our LX. I downloaded an entire set of step by step instructions from the Toyota technical site. I think I paid $10.00 for one day access to the site. Unfortunately, my wife threw away the pages I printed and I can't remember exactly how I did it. It was pretty easy, though. Do use a hose on the bleeder plug to direct the fluid into a catch bottle, as the emulsified fluid comes out under a great deal of pressure. Take a look at that Toyota site, the instructions are good.

[LEXUSBEN]

This is how we usually do it at work (no rocket science), just be careful you don't squish your melon!! One can of the ahc fluid is usually plenty.
1. Set the vehicle all the way to low (Reservoir full)
2. Remove all of the old fluid from reservoir. Fill with new clean fluid, I usually put the whole can in. 3. Start vehicle and let suspension equalize to "n" position.
4. Turn vehicle off.
5. Start at one of the back accumulators (doesn't matter which one) and using a hose on the bleeder, open very slowly and let weight of vehicle push fluid out. Close bleeder when vehicle is close to bottom.
THIS IS THE STEP YOU COULD GET SQUISHED IF YOU ARE NOT CAREFUL!!!
6. Start vehicle and repeat steps for each corner accumulator.
7. Usually one cycle at each corner is sufficient. If you are going to do it more than once you will need more than one can of fluid.
Cautions - don't crack bleeders while car is running. Vehicle will try to compensate for the leaking corner and you will have a big high pressure mess.
Fluid resembles very slippery brake fluid and is a PITA to clean up - so keep that in mind.
Also this is usually PM at 60,000 miles.
Questions let me know.

[hoser]

EDIT:
When following the steps above (specifically #5), Ben meant to say "start at one of the back 'Damping Force Actuators.'" See the diagram in Post #1 to see what it looks like. I also bled the "Height Control Accumulator" and did that till the fluid ran clear. Though I'm not sure it was necessary.


LexusBen-You said this is normally done at 60K intervals. Is that standard for all Lexus Dealerships or just yours? I've never seen it mentioned on the 60k service.

CTapia, It was pretty easy to adjust the height. I will post what I did so far but I'm still not quite done fiddling with the system.

[LEXUSBEN]

I've worked at dealers in Portland, SLC, and Denver and they all did it. Sometimes california dealers are lighter on the Maintenance because the weather isn't as extreme. I just looked in the Maintenance recommendations from the factory and 02 didn't list anything but, 04 updated and lists AHC replacement every 60k. I can e-mail you the pdf if you want.

[CTapia]

Originally Posted by LEXUSBEN

I've worked at dealers in Portland, SLC, and Denver and they all did it. Sometimes california dealers are lighter on the Maintenance because the weather isn't as extreme. I just looked in the Maintenance recommendations from the factory and 02 didn't list anything but, 04 updated and lists AHC replacement every 60k. I can e-mail you the pdf if you want.

I'll take a copy of the PDF, I'll P.M you my e-mail address.

[Jim_Chow]

How about posting it for the archive?

[hoser]

It's a PDF file so somebody will have to host it.

[LEXUSBEN]

You guys figure out how to put it up and we'll do it.

[FinallyGotOne!]

LEXUSBEN! THANKS!!

Note: My 2000 owner's manual lists AHC suspension fluid replacement as a 60K mile service.

[tabraha]

So who's got the pdf? Somebody shoot it to me and I'll attempt to host it.
PM me so I can shoot someone an email address.

[hoser]

PM sent

[tabraha]

Gotcha.

[NMuzj100]

Originally Posted by Landpimp in another thread

Toyota has the AHC fluid, part # 08886-01805, $21 for 2.5ltrs. in stock at my dealer. not sure if its cheaper then lexus...but it can't be anymore.

I'm sure Cdan can deal in this stuff now that Toyota has the AHC on the new models.

[ZOX]

Originally Posted by hoser

PM sent

Can I get PDF too please.

[hoser]

Tad posted the Maintenance Schedule PDF here.
http://forum.ih8mud.com/100-series-cruisers/60777-lx470-maintenance-log.html

I have no PDF on how to change the AHC fluid. Just follow the guidelines in post #6 of this thread.

[ZOX]

Hoser, thanks anyway, All this info about AHC is very usefull for us, lucky AHC owners

[uHu]

tnx to lexusben, hoser & tad for the AHC fluid procedure, it looks like i will need it.

But what about the fluid in the shock absorber, and in the pipe leading to it?
I guess that liquid could need replacement as well. And it would probably take years for it to naturally mix with the rest of the fluid.

It looks like I have a serious issue with wrong fluid in the system. Needed a top-up three years ago, and again earlier this year, was told by toyo-dealer to use brake fluid.... dot4 - not dot5....
Over time this liquid has worked it's way down to where it is actually doing some work, with the result of no shock absorber effect, because that fluid is too "spongy".
Now, if I only change the fluid in the tank, and down to the bleeder plugs, I presume the ride would be just as spongy afterwords, because only the oil beyond that point actually carry the weight of the vehicle. Would I have to drain the shocks themselves? Is there much of the fluid inside them? And I guess I could drain the pipes between the Damping Actuators and the shocks, but would there be a problem of air inside afterwards...? What else...?

Any comments?

[hoser]

Welcome uHu! Nice to see more and more non-US members. I'm always interested in the differences in models.

As for the AHC fluid, I'm not sure what to tell you but I'll ramble some thoughts. I would have guessed brake fluid to be very similiar to the AHC fluid since they both work at high pressure and temperature. Brake fluid is not "spongy" at all but the brake system can get spongy when there is air in the system.

Have you tried to bleed your actuators and accumulator? When you bleed the system, the suspension compresses completely to the bumpstops. So what's left is the remaining fluid in the shock and the line that goes from the shocks to the actuators. Of course, the only way to get ALL of the brake fluid out would be to remove the shocks/brake lines and bleed them out. But if you were to flush the system out say 2-3 times waiting a couple days between flushes, I would think you'd be able to get 95% or more of the brake fluid out.

Perhaps, one or more of your actuators have gone bad and that is the real cause of your AHC failure? How does the ride feel?

[uHu]

Tnx hoser
Well, I did think it reasonable to use brake fluid at the time. Currently my local toyo dealer is trying to find out if brake fluid was ever officialy recommended as a replacement, although this is a different dealer than the one who told me to use it some time ago.
The ride is like no shocks at all in the front!!! And i suspect the rear is starting to fail as well. Difficult to tell because of the way the front sways up and down for every little bump, not to mention the bigger ones (complete take-off and loss of control).
The problem started around 54' km (33k mi), and a tech at the dealer said the shocks might be shot. So I got a deal with the dealer where I bought the car (far from here) to supply new front shocks free of charge, since this was just after the end of the 3 year warranty period, but only IF they where changed at a recognized toyo workshop. So, I paid half a fortune for shipping/customs, and have a bill for the change of shocks, but same problem....
Anyhow, the dealer bled the system and refilled some fluid in connection with changing the two front shocks, and I bled once on each front actuator, letting it go all the way down from normal height. I'll try some more bleeding, rear and height accu.
I would have liked to see a full overview and description of how the system works; then there would be no problem, only nice work. But, as far as I can understand, if the actuator unit is blasted then the ride gets very stiff, which is the opposite of what I have. Air sounds more probable. Of course one of the valves in an actuator could be out of order, but on both sides? Will check the solenoids of the actuators anyhow (simple ohm check, 13 ohms on each of 4 solenoids in each actuator).
BTW the toyo tech currently dealing with,,, says the two oils/fluids feel very different, the AHC fluid more oily, like a normal hydraulic oil, and the brake fluid much drier.
I wonder how this will end....

[hkeller]

Greetings. I am having the same problem with my LX 470. The best I can tell, the damping force actuators, which are the small sphere shapped things on the frame rail, have gone bad. These are round chambers with fluid on one side and nitrogen on the other, separated by a thick membrane. These are what damp the bounce when you go over a bump. One person told me that brake fluid would dissolve the membrane and allow the nitrogen to leakout, thereby casuing the trouble you describe.

[uHu]

tnx keller.
Any idea about the solution to that problem?
Change the spheres? Or is a rep poss.?

Some thoughts on the matter: Nitrogen leaking out? That would mean into the fluid. That would be like air bubbles. But wouldn't they rise to the surface over time? And the nitrogen chamber would then be empty, flat, resulting in very hard suspension? Or would there be microscopic bubbles in the fluid?
Enough of my ramblings. Does this make any sense???

[hkeller]

Good questions, I don't know where the bubbles go.

There is a man in the US, Keith Bowers that drills and taps the sphere, installs a one way valve and recharges the nitrogen. He cannot, however, replace the membrane. New spheres cost about $550US, so you are looking at $2000 plus to replace all 4. Keith Bowers charges $150 to recharge them. He does not charge you if he test of the sphere indicate it will not hold a charge. If you do a search you'll find his email somewhere on this forum. I had it, but misplaced it.

[hoser]

uHu, the other option for you is to replace the suspension with an aftermarket set-up. The parts can be had for $700-900US plus installation. Of course, you'll lose all the AHC features but you'll gain reliability. Because it is difficult/expensive for you to get Toyota Parts, I think this might be your best option.

For technical information on the AHC suspension, you'll have to subscribe to one of the following services.

http://www.techinfo.toyota.com/
http://techdoc.lexus-europe.com/

[uHu]

OK, some new info on my AHC issue. (See previous postings)
I have now replaced the AHC fluid. The old fluid looked vile, dark brown at the accumulator and grey at the actuators. Anyhow, that was a mix of brake fluid and the original AHC fluid. I took out what I could from the reservoir, filled new fluid in and drained from all the bleeder plugs. Added more fluid and drained again. Then I took off the front shocks, emptied them and sucked them full of new fluid before putting them back on.
BTW, on top of the shock, where it connects to the AHC fluid-pipe, there is supposed to be one o-ring and one back-up ring, according to the drawing and parts list. I found only one o-ring. Has anybody seen a back-up ring? What does it look like?
Moving on to the rear shocks, I found that I couldn’t do it without a proper lift, as you have to get your shoulder all the way up under the body in order to get a couple of fingers in to the small bolts of the AHC pipe. (Well, maybe I could have, but with great difficulty). So, I decided to try without emptying the rear shocks completely, as I had only my home garage floor available.
Then I pumped AHC fluid into the system again, using the “Active Test” as described in the Rep.Manual, keeping an eye on the fluid level. And then some checking, full bleeding cycle, and then ROAD TEST. Well, it seemed to be a bit better in the front, but the rear... Worse than ever. Back to base, more bleeding, but out of AHC fluid. Used 2 cans altogether(2.5 litre each). Anyhow, ride did not improve.
Today I got 2 more cans, did a thorough bleeding, even followed the manual this time (the procedure is described slightly different from what appears earlier in this thread). Road test: - no improvement.
Then - AHA: Somebody in this forum mentioned the hydrogen chambers - spheres - attached to the actuators. Thanks hkeller . Looked in the Toyota manual, found a simple test: “How many graduations on the AHC fluid reservoir is used when changing from LO to HI?” The answer should be “more than 7". “Otherwise change all four spheres.”
I got a change of only 4 graduation marks. So, 4 new expensive spheres.
Does anybody know wether they can be changed without taking off the actuators? Meaning: is there space to unscrew them otherwise?
Are there many out there who have had the same experience?