LX570 AHC “Basics” - Added as sticky thread for AHC Issues (11 Viewers)

[TeCKis300]

Gotcha, thanks. Are there any other bushings or anything else that would be good to replace while changing the accumulators or shocks? If i'm in those areas, I'd rather take care of anything that is easy to change. And it sounds like some say that the shocks should be replaced in pairs, and others say just the one that is leaking.

I would at a minimum change the front pair of shocks. If money's not a big deal, change all 4 and you won't have to worry about it again. Shocks are pretty cheap on the LX (fronts ~$200per, rear ~$100/per). Globes depending on where you source it $500-$2k/set. Fluid ~$100-200.

That's all I would do. My LX has 140k miles and I'm actually in the middle of this operation of changing out all shocks and accumulators. Not cause anything failed but taking the opportunity to mod and refresh. Bushing look actually pretty good. If you want to change those that are a part of the upper shock mount, I think that's about another $140/shock.

It's the labor that really adds up.

 

[joesrcool]

Last week I completed an AHC flush and I didn't really have any issues. The flush was very straightforward and I was happy to get the old nasty fluid out. There was no history on this vehicle having an AHC flush done, and at 110k miles the fluid was very dark and possibly slightly low. I ended up using a full 5L of fluid during the flush as I never really felt the new fluid was coming out clean. I bled each corner three times before moving onto the next. During the first bleed at each corner, the fluid contained a bunch of tiny little air bubbles. The each bleed after that had cleaner, bubble-free fluid.

That brings me to a few days ago when I came out of the store and the front-right corner was all the way low, and the truck was leaning. All three other corners looked normal, except for the front-right. I cycled through the various heights and it seemed to stutter, which it didn't do prior to the flush. I'm almost positive no air was introduced as I kept the reservoir pretty full. Most of the time the truck is great, but every now and then, I can tell something is off at one of the corners as all of the sudden my steering wheel goes approximately 30-degrees off when driving straight. This can be remedied by cycling through the height settings, but I think something is amiss.

I've got another 2.5L of fluid coming in, and I was going to just do a simple bleed at each corner. Anything else I should check?

 

[lx200inAR]

Last week I completed an AHC flush and I didn't really have any issues. The flush was very straightforward and I was happy to get the old nasty fluid out. There was no history on this vehicle having an AHC flush done, and at 110k miles the fluid was very dark and possibly slightly low. I ended up using a full 5L of fluid during the flush as I never really felt the new fluid was coming out clean. I bled each corner three times before moving onto the next. During the first bleed at each corner, the fluid contained a bunch of tiny little air bubbles. The each bleed after that had cleaner, bubble-free fluid.

That brings me to a few days ago when I came out of the store and the front-right corner was all the way low, and the truck was leaning. All three other corners looked normal, except for the front-right. I cycled through the various heights and it seemed to stutter, which it didn't do prior to the flush. I'm almost positive no air was introduced as I kept the reservoir pretty full. Most of the time the truck is great, but every now and then, I can tell something is off at one of the corners as all of the sudden my steering wheel goes approximately 30-degrees off when driving straight. This can be remedied by cycling through the height settings, but I think something is amiss.

I've got another 2.5L of fluid coming in, and I was going to just do a simple bleed at each corner. Anything else I should check?

random thoughts from a guy who is not a mechanic on the internet…

If you had a corner lose height while parked at a store, and there wasn’t a puddle of fluid on the ground, I’d be getting Techstream and checking for suspension DTCs. theres only a few possibilities.

I’ve had the steering wheel thing happen after I’ve messed with my height sensors, usually after driving a few blocks it rights itself.

maybe you have a height sensor giving you trouble. The truck shouldn’t adjust much while parked, but possibly you didn’t notice it lower While you were still in it. Either way, if you intend to look at it yourself, techstream will be your friend.

 

[joesrcool]

random thoughts from a guy who is not a mechanic on the internet…

If you had a corner lose height while parked at a store, and there wasn’t a puddle of fluid on the ground, I’d be getting Techstream and checking for suspension DTCs. theres only a few possibilities.

I’ve had the steering wheel thing happen after I’ve messed with my height sensors, usually after driving a few blocks it rights itself.

maybe you have a height sensor giving you trouble. The truck shouldn’t adjust much while parked, but possibly you didn’t notice it lower While you were still in it. Either way, if you intend to look at it yourself, techstream will be your friend.

You are correct, it definitely could have lowered that corner while on the way to the store or while in park getting out. I didn't notice that one corner low until coming out. No leaks from the shock, or any other areas. I should have mentioned, I don't have Techstream up and running quite yet, but there have been no AHC errors in the dash.

I did mess with the height sensors to see what adjustment range I had, but I then set them to the factory recommended height settings. I also thought it may be a height sensor giving me that issue.

I'll let you know if there's anything glaring when I crack the bleeders at each corner.

 

[joesrcool]

Little update, did a quick bleed at each of the corners and all was clear and bubble-free, except for that front-right corner. I ended up bleeding a bit more out as there was a bunch of little tiny air bubbles and it almost seemed as if it were foaming. Once the fluid cleared up, I stopped. Made sure the reservoir was topped off, and I'm just over the Max line in N. I have a short road trip coming up, so we'll see how it performs.

 

[Wolvie]

I would at a minimum change the front pair of shocks. If money's not a big deal, change all 4 and you won't have to worry about it again. Shocks are pretty cheap on the LX (fronts ~$200per, rear ~$100/per). Globes depending on where you source it $500-$2k/set. Fluid ~$100-200.

That's all I would do. My LX has 140k miles and I'm actually in the middle of this operation of changing out all shocks and accumulators. Not cause anything failed but taking the opportunity to mod and refresh. Bushing look actually pretty good. If you want to change those that are a part of the upper shock mount, I think that's about another $140/shock.

It's the labor that really adds up.

This is all on my list. I'm wondering what order you're doing this in. Shocks first, last?

 

[amunsey]

This is all on my list. I'm wondering what order you're doing this in. Shocks first, last?

My current plan is to do front shocks as the first step. The only real reason for this is because this is the only thing I can't do myself. I'll need either the Lexus dealer or my independent shop to handle this part. Then I'm planning on changing the globes and finishing off with the AHC fluid flush once all the new parts are installed.

However if anyone has different thoughts, I'd love to hear them. Still educating myself on this whole system. I also need to find the instrictions for replacing the shocks in the case that I take it to my indy shop rather than the dealer.

 

[teejnut]

SQOD. Is there a point of pre-emptively changing the AHC shocks? Is it a "wear" item? Or doesn't really need any maintenance unless it starts to leak of course?

 

[grinchy]

SQOD. Is there a point of pre-emptively changing the AHC shocks? Is it a "wear" item? Or doesn't really need any maintenance unless it starts to leak of course?

my understanding is they work all the same (new vs old, high miles vs no miles), until they leak.

 

[lx200inAR]

My current plan is to do front shocks as the first step. The only real reason for this is because this is the only thing I can't do myself. I'll need either the Lexus dealer or my independent shop to handle this part. Then I'm planning on changing the globes and finishing off with the AHC fluid flush once all the new parts are installed.

However if anyone has different thoughts, I'd love to hear them. Still educating myself on this whole system. I also need to find the instrictions for replacing the shocks in the case that I take it to my indy shop rather than the dealer.

The only real issue is going through so much fluid. But if you are okay with that, then it doesn't really matter what order you go in. Changing globes and shocks at once would only require a flush/bleed once. Changing the shocks isn't different than any other Toyota, with the exception of depressurizing and disconnecting the hydraulic line from the top of the shock, so i wouldn't be worried about using your preferred mechanic, assuming they were comfortable with it. I also wouldn't assume the guys at your dealership have changed out many more AHC shocks than your other mechanic.

If your independent is someone you are comfortable with, it may not be a big deal to get them to change the globes while they have the shocks out, at least on the fronts, since the system will already be depressurized.

SQOD. Is there a point of pre-emptively changing the AHC shocks? Is it a "wear" item? Or doesn't really need any maintenance unless it starts to leak of course?

From what i understand, the AHC "shock" is little more than a hydraulic ram. All the valving and bouncy bits are attached to the frame. So other than the bushings and them not leaking, there isn't much to be replacing.

 

[tincan45]

my understanding is they work all the same (new vs old, high miles vs no miles), until they leak.

That is my understanding as well. They are just passive tubes with a very small elastomer shock at the end to help in a bottom out/ low pressure scenario. All the active suspension is transferred to the globes hydraulically. If they are not leaking and the bushings all look good, I'm not inclined to change them. Perhaps someone more knowledgeable can chime in if this is incorrect.

If I was going to change them, I would pre-flush them with clean fluid before install to avoid any possible contaminants.

 

[TeCKis300]

This is all on my list. I'm wondering what order you're doing this in. Shocks first, last?

I'd do them all at once if that's your goal. As pointed out by @lx200inAR , if you're going to depressurize the system, that's the right time to attack everything.

That said, IMO shocks don't really need to be addressed unless they're leaking. Globes would see more wear and would be good to change around ~150k. Fluid of course has a maintenance interval of every 60k.

I would bet a number of people having leaking shocks is due to globe failure. Once the pressure inside the globes is lost, and or the membrane ruptures, "bottoming out" of the hydraulic system on the globes is a real thing. This can cause hydraulic pressures to really spike, potentially wearing/damaging the seals on the shocks causing them to weep/leak.

I just drove my car on this morning for the first time after the once over. Man, was surprised at how much better the ride is. It was pretty awesome before even with LT-E tires, but it's another 20-30% better, especially on the smaller bumps. Another layer of butter. Raising and dropping heights is almost 2x as fast. I'll go into details later as the whys, but short answer is fresh globes can make the biggest difference. And they're probably the easiest to change if depressurizing the system with (another 1hr of work).

 

[Bryanmc]

Review on my situation:

- RR damper actuator bad
- Line nut rusted/rounded making removal and reuse difficult or impossible

The shop's solution is to replace the entire line, which will require dropping the gas tank. All in all, I'm just happy to have a solution at this point.

QUESTION:

Is there anything at all that I should do or have done while the tank is dropped. Anything to replace, or inspect? Vehicle has 135K, more rust that I originally thought when I bought it, making some repairs difficult. I plan to keep this thing as long as possible.

Just to put a bow on this, got the vehicle back today and all is well! They replaced the line, installed the used replacement damper assembly and my buttery ride is back. They also did a complete AHC flush, so I could have saved myself from doing that a couple months ago. What a mess this was, glad it's over.

 

[lx200inAR]

Just to put a bow on this, got the vehicle back today and all is well! They replaced the line, installed the used replacement damper assembly and my buttery ride is back. They also did a complete AHC flush, so I could have saved myself from doing that a couple months ago. What a mess this was, glad it's over.

Awesome! glad it all got worked out. And to think you didn't even have to shell over $30k to your local Lexus dealer.

 

[32cls6speedmt]

Just to put a bow on this, got the vehicle back today and all is well! They replaced the line, installed the used replacement damper assembly and my buttery ride is back. They also did a complete AHC flush, so I could have saved myself from doing that a couple months ago. What a mess this was, glad it's over.

That is fantastic news. I am sure you are relieved. I hope you share the contact information for this mechanic shop in the clubhouse section of this forum.

 

[TeCKis300]

Interesting detail I learned today. AHC Extra high (+3.1" or 80mm) not only engages when the system detects a stuck, but also during CRAWL function.

With an 1.5" sensor lift, that makes for 4.6" total lift on the hard stuff.

With 35s, that 6.6" total lift.

 

[lx200inAR]

Interesting detail I learned today. AHC Extra high (+3.1" or 80mm) not only engages when the system detects a stuck, but also during CRAWL function.

View attachment 3030253

With an 1.5" sensor lift, that makes for 4.6" total lift on the hard stuff.

With 35s, that 6.6" total lift.

I’ve read that before and go back and forth on whether it still requires the ECU to see “slip” before it engages.

Using the AHC tool in OBD Fusion, I get no height changes by just engaging Crawl, and the Height index does not change either. Extra HI is the only value I haven’t been able to get the index for because I haven’t been able to force it yet. Next time I’m in the muck I’ll try to find it.

Weird anomaly though today. I went out at lunch to test again to refresh my memory, and when I initially put my truck in high, it raised 80mm instead of 60m. About 60-90 seconds later at a stop light it lowered back to 60mm.. it’s possibly I was moving while it was lifting and it went to far and adjusted back down. It didn’t go that high again in any of the testing I did.

 

[TeCKis300]

I’ve read that before and go back and forth on whether it still requires the ECU to see “slip” before it engages.

Using the AHC tool in OBD Fusion, I get no height changes by just engaging Crawl, and the Height index does not change either. Extra HI is the only value I haven’t been able to get the index for because I haven’t been able to force it yet. Next time I’m in the muck I’ll try to find it.

Weird anomaly though today. I went out at lunch to test again to refresh my memory, and when I initially put my truck in high, it raised 80mm instead of 60m. About 60-90 seconds later at a stop light it lowered back to 60mm.. it’s possibly I was moving while it was lifting and it went to far and adjusted back down. It didn’t go that high again in any of the testing I did.

Yeah, I had always assumed there was slip criteria. The way the second bullet above is worded does not indicate that, with CRAWL enabled being sufficient.

The AHC dashboard is a great check. I'll try to do the same the next time I find a slippery hill.

 

[lx200inAR]

Yeah, I had always assumed there was slip criteria. The way the second bullet above is worded does not indicate that, with CRAWL enabled being sufficient.

The AHC dashboard is a great check. I'll try to do the same the next time I find a slippery hill.

I wonder if it’s a model to model variation. There have been at least a few different revisions of the suspension ECU.

 

[amunsey]

Well I've got the accumulators ordered from ebay and am in the process of ordering the new front shocks from a Lexus dealer in Georgia. Has anyone changed out the Upper Shock Mount bushing as part of this process? Is it pretty easy to do while the shocks are off? I can get each bushing for around $50. Part number - 9094801097

9094801097 - Lexus Suspension Shock Absorber / Strut Mount | Jim Hudson Lexus Augusta, Martinez GA

Genuine Lexus Part # 9094801097 (90948-01097) - Suspension Shock Absorber / Strut Mount Bushing (Left, Right, Front). FRONT SHOCK ABSORBER, NO. 1 LEFT; FRONT SHOCK ABSORBER, NO. 1 RIGHT. Fits LX 570. Ships from Jim Hudson Lexus Augusta, Martinez GA

parts.augustalexus.com