Changing out the AHC suspension fluid?

[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?

Edit: Do NOT use brake fluid in the AHC system. It will deteriorate the rubber membrane. This Motul fluid is probably closer to what Toyota/Lexus sells but for the price, why not just use OEM stuff.
http://www.motul.com.au/product_line_up/fork_brake_others/others20.html

 

[uHu]

Brake Fluid ?!?

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]

Nitrogen leaking out

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.

 

[uHu]

More AHC problems

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?

 

[hkeller]

Glad I could help. The spheres simply unscrew from the actuator. You may need a chain wrench or a belt wrench; a ground down open end wrench may also work. If you look closely, there is a large nut at the end of the sphere closest to the actuator, it's part of the sphere. The sphere's simply spin off. I hear they can be a bear to break loose. You can ship these to Keith Bowes, who's email is somewhere on this board, but I don't have it handy. He will recharge for $150.00 a piece. Beats the $500 plus the dealer will charge for each. The only problem is, the brake fluid may have disolved your membrane. Thereby making recharging not an open. I would suggest trying to source through a junk yard on a relatively new wreck. Keith will tell you whether yours will hold a charge and not bill you if they are shot. Since you are oversees, he may be willing to tell you the process of drilling tapping and recharging, so you can do it yourself. With the right equipment, it should be simple, if you know the pressure.

Best of luck. I wish it was better news.

 

[uHu]

Yes, that's a good idea. Found some used 60k miles, for $ 140 each, plus shipping. Those might be complete actuators though.
I have no idea how long they should last. Is 60k too much?
Anybody?
So, the spheres should be possible to remove without removing the actuators. Looks a bit tight on the left side though.
Right now, the suspension is "rather uncomfortable".... (see, no bad words)

 

[ZOX]

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.”

Can you please tell me something more about this simple testing, and maybe some other testing procedures from your Toyota manual regarding AHC. I always wonder why is those marks on a reservoir can. Tnx.

 

[uHu]

OK. The test for the spheres (gas springs) has the following conditions (at least):
1 - The vehicle height is correct in L, N and H.
2 - Any air in the AHC fluid has been bled.
(Other factors like spring tension (shock absorber neutral pressure), enough fluid, etc...)

Test:
1 - Adjust height to LO
2 - Record fluid level in reservoir (front left corner (of the reservoir)[edit])
3 - Adjust height from LO to HI
4 - Note the difference in fluid level

The change should be 7 graduations or more. (8 or more for OZ !!)

Can come back with more tests/info next year.

 

[uHu]

New AHC gas chambers

Four 2nd hand gas chambers fitted just in time for the holidays.
Got them from Denmark http://www.joekers.dk/
Easy job, and very rewarding. All you need is a 36 mm spanner, ground down to 8 mm thickness. (In addition to the bleeding eq)
Now the gas spheres test reads about 7.5 grads.

It's wonderful to drive again. Had forgotten how good this AHC/TEMS suspension really is.

 

[Jim_Chow]

I regards to when to replace the AHC fluid, I noticed the owners manual for my '03 LX says to replace the AHC fluid at 60K miles.

 

[ZOX]

Thanks to all you folks who gave advices regarding changing AHC fluid. I was a bit lazy this winter, but after few warm days I decide to finally change AHC fluid. I follow the previous explained procedure and it’s a piece of cake. My old fluid looks like metallic gray paint (after almost 187.000 mls) and new one is pure, crystal yellowish liquid. Main thing is after flushing the system my suspension works like brand new!! Great improvement! Thanks again and I love my AHC (again).

 

[Tinkerer]

Thanks to all you folks who gave advices regarding changing AHC fluid. I was a bit lazy this winter, but after few warm days I decide to finally change AHC fluid. I follow the previous explained procedure and it’s a piece of cake. My old fluid looks like metallic gray paint (after almost 187.000 mls) and new one is pure, crystal yellowish liquid. Main thing is after flushing the system my suspension works like brand new!! Great improvement! Thanks again and I love my AHC (again).

What kind of improvement did you notice?

I'm going to change my AHC fluid this weekend, I guess...about time, at 96k miles.

Anyone have the Toyota p/n for the fluid? (The Lexus stealer will charge up to 40% more for the same p/n as Toyota, in my experience.)

 

[hoser]

AHC Fluid Toyota Part #08886-01805

 

[Tinkerer]

AHC Fluid Toyota Part #08886-01805

Thanks - this helped speed up the phone work yesterday!

Strangely, the Lexus price quote was only 5% higher than Toyota, for the 2.5L can. (Usually Lexus charges 30 to 40% more for same p/n.)

Waddya think - should I support my local Lexus dealer by buying from them and paying their additional premium? hehe

Can anyone comment on ride quality affect by old vs. new AHC fluid?

 

[LXPearl]

The can you get from Lexus will be the same Toyota branded can you buy from Toyota. I bought mine from Lexus, but I also got it for less than I could at the Toyota dealer. Your choice on who you buy from - its the same product.

 

[ZOX]

Can anyone comment on ride quality affect by old vs. new AHC fluid?

As I said, ride become smoother and kinda softer in all conditions (in normal position), and better harder feeling in sport position without any bump noises. After flushing fluid I was also on a suspension tester, and this tester according to data in memory find minimum difference between mine suspension and brand new one. Suspension test find wear out of link assy of front stabilizer, and after I change this my rig become kinda hovercraft

 

[hoser]

Tinkerer, by any chance can you measure the length of the front and rear AHC shocks at full suspension compression? When you bleed the actuators, your suspension will lower completely to the bumpstops.

I'm also looking for the measured length of the AHC shocks compressed and extended. Anybody have a uninstalled AHC shocks?

 

[Tinkerer]

Tinkerer, by any chance can you measure the length of the front and rear AHC shocks at full suspension compression? When you bleed the actuators, your suspension will lower completely to the bumpstops.

I'm also looking for the measured length of the AHC shocks compressed and extended. Anybody have a uninstalled AHC shocks?

What measurement points?

(I bled it last night but one can of fluid was not enough, so now I have to re-do it with 2 or 3 cans...can measure things then...)