AHC woes

[Das Shtig]

Double post — Deleted

 

[Das Shtig]

Ok, got it back, the clunk is quieted but not gone, and I’m ok with that. They put a wrench on everything under the car and torqued it all to spec. They readjusted my torsion bars and got my pressures in spec. It feels quiet and smooth and excellent — although the clunk is occasionally heard.

BUT, since I got it back, the AHC is moving VERY slowly. At first it was just a little slower, but now it’s taking waaaay longer, like more than a minute. Pump failure? What am i looking at here? Could they have possibly caused this? Paging @PADDO ::crying::

 

[Das Shtig]

So the saga continues...

All the dealership’s testing wore out my AHC pump. They’re telling me now I need a new AHC Pump & Motor Assembly and a Height Valve Assembly.... grand total at the dealership $4618. The parts alone are about $3700. Someone, somewhere, maybe @PADDO, please help me out... what are my options. How can I fix this for less than $3700

 

[PADDO]

So the saga continues...

All the dealership’s testing wore out my AHC pump. They’re telling me now I need a new AHC Pump & Motor Assembly and a Height Valve Assembly.... grand total at the dealership $4618. The parts alone are about $3700. Someone, somewhere, maybe @PADDO, please help me out... what are my options. How can I fix this for less than $3700

I’ve not read anything yet that suggests to me the dealership has any real idea or plan to what they are doing - seems like misdiagnosis and just throwing parts at it. What started out as a “clunk” appears to have snowballed. So let’s decouple the issues and move on from “shocks” causing a clunk, that wasn’t the root of the problem. It’s something else and not AHC related I bet.
Now just focusing on slow L->N->H. Book says 15 seconds per lift segment for a stock vehicle, what are your actual times? Just off the top of my head things that affect this systems, or any hydraulic servo system for that matter, dynamic performance are:
1. Fluid viscosity and temperature, air in the system - did they pre fill the “shocks” they replaced with AHC fluid and conduct a proper bleed? Dumb dumbs fit hydraulic components dry and wonder why things don’t work properly and the system is full of air. Using a heavier weight fluid than the very light AHC fluid (which is not only a hydraulic working fluid but also has to function as a shock/fork damping oil) will impact performance too.
2. System preload pressure - aka neutral pressures - too high neutral pressures requires the pump to work harder and longer. What are your neutral pressure, please don’t just say “in spec”. At one stage you said you and a buddy cranked TBs to change height/cross level but didn’t tune the system to the correct hydraulic pressure so you could have inadvertently over cranked the system which masked other issues and if the dealer reset,lowered, your front pressure then a prexisting problem could then manifest.
3. What is your height accumulator pressure? Your height accumulator stores pressurized fluid to augment the pumps output during a lift. If it’s failed (there’s a service bulletin on the subject for pre 03 vehicle’s) you’ll have very slow lift rates. A healthy height accumulator should charge to 10.4MPa +/-0.1 and discharge about 400ml from the charged state when the fluid is bleed off via the bleed port. In the service bulletin it discusses how the pump can be internally blocked by seal material that’s sloughed off the height accumulators main seal so it’s a definite possibility you’ve got a blocked up pump intake and/or a flat height accumulator, particularly if you’ve got a pre “fixed” vehicle.
4. The systems solenoid valves can be cycled in the AHC utilities section of Techstream, which can be useful. As is being able to monitor the systems feedback parameters and DTCs. Solenoids can also be operated manually in test mode.
5. If your height accumulator fails the basic tests then a serviceable replacement takeoff can be had for very little, so can a takeoff pump/reservoir assembly. Regarding the “height valve” I’m not sure what they are referring to. The height accumulator has its own solenoid valve that’s integral to the unit; the other valve they may be referring to is the main valve block that houses the leveling and gates valves. Unlikely it needs replacing. Just the pump can be purchased new for about $200. For the money the dealer is talking about, with no guarantees, and if you can’t fix it yourself then I’d seriously consider crossing over to the dark side and going conventional.
6. Investing in the FSMs and Techstream is pretty much mandatory imo for diagnosing the system.

 

[Das Shtig]

I’ve not read anything yet that suggests to me the dealership has any real idea or plan to what they are doing - seems like misdiagnosis and just throwing parts at it. What started out as a “clunk” appears to have snowballed. So let’s decouple the issues and move on from “shocks” causing a clunk, that wasn’t the root of the problem. It’s something else and not AHC related I bet.
Now just focusing on slow L->N->H. Book says 15 seconds per lift segment for a stock vehicle, what are your actual times? Just off the top of my head things that affect this systems, or any hydraulic servo system for that matter, dynamic performance are:
1. Fluid viscosity and temperature, air in the system - did they pre fill the “shocks” they replaced with AHC fluid and conduct a proper bleed? Dumb dumbs fit hydraulic components dry and wonder why things don’t work properly and the system is full of air. Using a heavier weight fluid than the very light AHC fluid (which is not only a hydraulic working fluid but also has to function as a shock/fork damping oil) will impact performance too.
2. System preload pressure - aka neutral pressures - too high neutral pressures requires the pump to work harder and longer. What are your neutral pressure, please don’t just say “in spec”. At one stage you said you and a buddy cranked TBs to change height/cross level but didn’t tune the system to the correct hydraulic pressure so you could have inadvertently over cranked the system which masked other issues and if the dealer reset,lowered, your front pressure then a prexisting problem could then manifest.
3. What is your height accumulator pressure? Your height accumulator stores pressurized fluid to augment the pumps output during a lift. If it’s failed (there’s a service bulletin on the subject for pre 03 vehicle’s) you’ll have very slow lift rates. A healthy height accumulator should charge to 10.4MPa +/-0.1 and discharge about 400ml from the charged state when the fluid is bleed off via the bleed port. In the service bulletin it discusses how the pump can be internally blocked by seal material that’s sloughed off the height accumulators main seal so it’s a definite possibility you’ve got a blocked up pump intake and/or a flat height accumulator, particularly if you’ve got a pre “fixed” vehicle.
4. The systems solenoid valves can be cycled in the AHC utilities section of Techstream, which can be useful. As is being able to monitor the systems feedback parameters and DTCs. Solenoids can also be operated manually in test mode.
5. If your height accumulator fails the basic tests then a serviceable replacement takeoff can be had for very little, so can a takeoff pump/reservoir assembly. Regarding the “height valve” I’m not sure what they are referring to. The height accumulator has its own solenoid valve that’s integral to the unit; the other valve they may be referring to is the main valve block that houses the leveling and gates valves. Unlikely it needs replacing. Just the pump can be purchased new for about $200. For the money the dealer is talking about, with no guarantees, and if you can’t fix it yourself then I’d seriously consider crossing over to the dark side and going conventional.
6. Investing in the FSMs and Techstream is pretty much mandatory imo for diagnosing the system.

By dark side you mean Land Cruiser non AHC shocks? I’m very interested in getting to the bottom of this and sticking with AHC. I’m already invested.

Regarding just replacing the pump, I asked he diagnostic specialist working on my car about this. I found a pump on CruiserParts for about $300, and I showed it to the DS, but he said I need the motor too. In order to type that last sentence I just went back to CrusierParts (AHC = Automatic Height Control : CruiserParts.net, Toyota Landcruiser Parts) and I noticed they offer the motor too, so I’ll ask the DS about this.

The valve they are recommending replacing “in order to do it all correctly” is part number 48940-60010. They didn’t say it was bad, just that they recommend replacing it when they do the pump assembly (48910-60012)

The AHC fluid was drained and refilled a few times during all their checks, and the DS admitted that this probably strained the high mileage pump and is why it’s moving slow. Heading to my car now to time this out for you:

Drove the car earlier but didn’t “use” (I know, it’s active, and being used constantly) the height control. Just to give you an idea of how “cold” the car is.

N>L=6.9 seconds. I’m surprised by this. I haven’t been using it since i noticed it working incorrectly, and previously it was taking much longer.

L>N=28.1 seconds. Yeah that’s slower than it used to be and more consistent with what I’ve been experiencing.

N>H=2 minutes in and the car doesn’t seem to be raising at all. Though I just dropped it back to neutral which lowered it slightly and only took a second.

Yes, I should probably get techstream. However I think the DS will share the info with me— will you tell me exactly what you’d like to know? I can probably have him tell me for free rather than spending even more money on something else. I get that it’s a good investment and I’ll make it here soon but I am a little tight right now so... idk if possible let’s try this “free” approach first?

 

[PADDO]

Here is a copy of the service bulletin I referenced, possibly your DS (diagnostics specialist? back in the day we got by with the lowly title of Technician) is not familiar with it and the ability to just change the pump. If it were mine I wouldn’t really contemplate changing out functional valves blocks but it sounds like that’s the plan your DS wants to follow. With this system you often need to eliminate what’s not defective in conjunction with looking for what is defective. The info that I was after - pressures and height accumulator parameters - as per #43. Good luck with it all.

 

[Das Shtig]

Here is a copy of the service bulletin I referenced, possibly your DS (diagnostics specialist? back in the day we got by with the lowly title of Technician) is not familiar with it and the ability to just change the pump. If it were mine I wouldn’t really contemplate changing out functional valves blocks but it sounds like that’s the plan your DS wants to follow. With this system you often need to eliminate what’s not defective in conjunction with looking for what is defective. The info that I was after - pressures and height accumulator parameters - as per #43. Good luck with it all.

Thanks for the TSB. I will get with my DS and go over all of this with him.

DS- Diagnostic Specialist, yes. However this title is different than tech. This guy is the only DS in the building, he is sort of the ‘Dr. House’ of the service department. So the DS and the service Manager have been the ones helping me since I walked in there a few weeks ago, and they’ve been pretty great, I do trust these guys. I could be wrong, it’s possible! But for now I’m operating on the assumption that these two guys are the most competent team I currently have at my disposal (along with you and the rest of the mud resources), and they’ve been under my truck for weeks going over eeeeverything so I feel like the also know my truck inside and out, which makes me want to continue using them, at least for now. Plus I have a credit with them for like $400 so I’ve got some diagnostic time to play with. But there’s no chance of me spending $5000 on this or anything else with them, either.

 

[Das Shtig]

Ugh they’re being really annoying about the fact it’s a Toyota TSB and not Lexus and they don’t have it in their system. That’s odd though that Toyota never sent this to Lexus dealers, right?

And to make sure I’ve got this right—the relevant part of the TSB is that the dealer is actually able to disassemble the pump&motor assembly and replace just the bad parts (i.e., just the pump and motor, rather than the entire assembly for $2,800)? This is a brilliant find @PADDO thank you! Now to convince them an LX470 is just a Land Cruiser...

 

[Das Shtig]

Convinced. The tech came in and said “duh, it’s a LC, so let’s try this if you want.” So, despite not having this TSB in their system, and never having disassembled the assembly, they’re honoring it. They’re gonna figure out what kind of time it should take them and what parts and related o rings etc they need to do the job and let me know the estimate... They’re going to cut me a big break on the labor but i guess the parts are what they are. They’ll also be applying my credit... so hopefully the cost will be reasonably low.

I gave the service advisor a list of few questions on Friday, including a request for neutral and accumulator pressures. However, I forgot to ask when I sat down with them today. I’ll ask next time I see them. But, the tech that I spoke with today did mention that he had previously checked the accumulator (I guess they thought maybe that was the problem and tested it) and it was operating properly. I’ll find out if that means the pressures were known to be good.

 

[Das Shtig]

Just took it back in to have them check the neutral and accumulator pressures with techstream. The whole time the service manager was telling the tech what I was wanting, the techs eyebrows and face were like, “you want me to do WHAT?!” Lmao. Guess they’ve never had this request before.

Ok the tech that worked on my car last time already had the values. Off the top of his head (he has it written down somewhere and I asked for those exact values) he said the front was 7 and the rear was 6.5. He said he’d already adjusted the front TBs slightly but that overall my springs and TBs were ok and not in need of replacement. He said the accumulator pressures up great but it takes a long time to get to the correct pressure because of the slow pump. Before discount and credit the cost to replace the pump and two o rings is $992. Waiting to hear what my price will be.

Btw @PADDO the TSB you provided says to replace the accumulator too... but you’re not suggesting I replace that, correct? Currently I’m just looking at replacing the pump sub assembly.

 

[Das Shtig]

From the tech:

FRONT PRESSURE IS AT 6.9-7MPA AND REAR IS AT 6-6.2KPA AT REST. AFTER ACCUMULATOR PRESSURE LOWERS , IT TAKES A LONG TIME FOR THE PUMP TO BUILD PRESSURE

 

[05JLX470]

Such a bummer with this being at a dealership that they are this confused. It's not like it's a 30 year old car. You would sure think they would have a tech that has been around for 15-20 years that is familiar with these vehicles. Good luck and keep us posted.......

 

[white_lx]

Hydraulic gear pumps typically fail gracefully as they gradually wear out from contamination or cavitation. To have this problem now all of a sudden is unlikely to be a pump problem, unless:

1. The pump motor is wearing,

2. The pump is blocked (on the inlet); cavitation could occur as well if it is partially blocked.

3. The coupling between the electric motor and the pump is slipping. Is there a key that could have sheared or moved? I have never seen these parts apart so I don't know what kind of coupling there is.

4. From the TSB: "When installing the pump sub−assembly, if applying unnecessary force to the pump gear, it may result in making clearance inside the pump, unsabling the fluid pressure to rise.". Unfortunately I have no clue what they mean by this (note: unsabling).

5. Specifically for the pump assembly on these vehicles with integrated return valve: If the return valve was bypassing, there could also be fluid loss from the pump directly back to the reservoir. Is it possible that some contamination prevents the poppet return valve from completely blocking off the path to the reservoir?

I would also try to measure running amps to the pump motor with a clamp meter to determine the load on the pump from L>N and from N>H to see if that explains the large difference and inspect the coupling and the pump itself.

 

[Das Shtig]

Apparently there’s black particles all through the system. Replacing the motor didn’t help. Guess we’re gonna try the accumulator and the pump now... does tha sound right?

 

[Das Shtig]

I was planning to drive my family to Ohio (from FL) in the truck Wednesday.... is it a terrible idea to drive this thing with those black particles floating around the system? If possible, my cheapest option is DIY but I can’t get it done before the trip. Is it safe to drive you think? I know the truck won’t flip over or burst into flames but I don’t want to destroy any other AHC parts. Please advise. @PADDO ?

 

[Das Shtig]

Hey guys sorry to be a pain just let me know if it’s safe to head to Ohio tomorrow with the black particles floating around the AHC system. Sorta need to know if I’m good to go ASAP

 

[Das Shtig]

Buuuuuuuuuump

 

[uHu]

No can tell.
You can't expect anyone to say it's safe -- or not.
What's the size of these particles? What's the size of the smallest valves and passages in the ahc system?
Why don't you just clean it out before using the car?

 

[Das Shtig]

Well, I did clean it out—Lexus flushed it multiple times, but more particles appear, presumably coming out of the accumulator (o ring). Yes, I was indeed hoping someone could tell me if it was safe — I don’t know this system as well as many of you, and it seems like it could be safe to drive (I am driving it, just drove to Nashville today from Orlando and am heading the rest of the way to Ohio tomorrow... miiiight even hit a 4x4 trail along the way), but I just wanted an expert to let me know if I really had anything major to be worried about. Like, what would be worst-case-scenario? You could tel me that. I’m certainly not asking you to use telepathy to look inside my system and measure the particles, etc. just wanted an expert opinion since I’m not an expert and the folks at Lexus of Orlando/Winter Park evidently are not either. I had one day to figure out whether I could drive the vehicle I’ve planned for months to take, or if I needed to spend the day before my trip scrambling to make some other arrangements, which would be a bad way to spend the day before a week long road trip with my family. I hoped an expert might chime in right away and let me know. Someone in fact did get in touch and tel me it was 100% fine to drive, so I went on my way. I apologize if it is a stupid question. I, in fact, do not know what I’m doing.

 

[Das Shtig]

So, update time...

I’ve been driving the truck as-is since last update. I suspect my issue is the black particles floating around my AHC system. I say this because while stopped/parked, the AHC doesn’t always raise or lower (the light just blinks forever and never moves from N to H or N to L) but if I move the car a little bit, it generally works fine. (I’m thinking this means a little piece of something is blocking flow somewhere and then when I move the truck around, it slides out of the way and things flow as they should and the system does it’s thing.)

I would like to fix this once and for all. I don’t want to throw parts at it randomly. Can anyone take an educated stab at what I might need to replace to get this bih working properly again?

Maybe just the accumulator and flush/clean the lines out? Lmk your educated thoughts... thanks!