AHC Inop after fluid change 2007 lx C1751 and C1762 (2 Viewers)

[suprarx7nut]

Good afternoon my AHC friends! I got around to installing some 30mm spacers this afternoon. Install was straightforward. I fired techstream up and it brought my rear pressures down by 0.5. Not quite as much as I was hoping. Also strangely whenever I would go from Lo to N or N to Hi I would hear a beep / squeak from the height accumulator about 1/2 the time. I blead a quart thought but this did not seem to help. I took it for a short drive, about 1/4 mile and the beep/squeak is gone! I can hear a hiss as the from the accumulator as the pump stops but I'm pretty sure this is normal and I can only hear it if I have the window down. Strangely I checked my grads and shockingly I went from 8-9 grads to 12-13 grads! I almost don't believe that these original 13 year old globes are giving me 12-13 grads... any thoughts??? Also I am looking to tow a 5,000 lb travel trailer maybe 200-300 miles+ 3 people this summer. Do you think my AHC can handle this with rear pressure at 6.3? Do I need new springs? Thanks! Also for anyone looking for cheap spacers you can get Nolathalen 30mm spacers part number REV170.0008 right now on ebay shipped for under 40$ most others go for 75$+

The sound from the height accumulator could be from a squeaky portion of the piston. Might not be a problem. Fresh fluid might help.

Gradation increase - seems odd. I would be amazed in 13 year old globes produced 12+ grads. They should be about dead after 13 years of normal use. I'd test a couple more times and make sure you give the system time to fill the height accumulator (about 30-60 seconds after raising).

Towing: Tongue weight is critical. Between additional payload and tongue weight, the system can handle about 1100 lbs if pressures are in spec. Consider that gas, jump seats, cargo all play into pressures. If the trailer might have a lot of tongue weight, I'd consider installing King springs. If you remove the 30mm spacers and install King springs, you might drop about 2.5 Mpa. If you're going to tow with passengers, I'd aim for the bottom of the spec on an empty rig.

If you have access to the trailer before hand, hook it up and check pressures. You might be fine.

 

[aharlan001]

The sound from the height accumulator could be from a squeaky portion of the piston. Might not be a problem. Fresh fluid might help.

Gradation increase - seems odd. I would be amazed in 13 year old globes produced 12+ grads. They should be about dead after 13 years of normal use. I'd test a couple more times and make sure you give the system time to fill the height accumulator (about 30-60 seconds after raising).

Towing: Tongue weight is critical. Between additional payload and tongue weight, the system can handle about 1100 lbs if pressures are in spec. Consider that gas, jump seats, cargo all play into pressures. If the trailer might have a lot of tongue weight, I'd consider installing King springs. If you remove the 30mm spacers and install King springs, you might drop about 2.5 Mpa. If you're going to tow with passengers, I'd aim for the bottom of the spec on an empty rig.

If you have access to the trailer before hand, hook it up and check pressures. You might be fine.

The squeal is gone so I'm not worried any that. Fluid is fresh.

I'll check grads again already did 2x.

If I have a weight distribution hitch the tongue weight should be minimal right? I really don't want to go king because 99% of the time it's just me in the vehicle without aftermarket weight and I don't want to compromise ride quality if I don't have to.

 

[suprarx7nut]

The squeal is gone so I'm not worried any that. Fluid is fresh.

I'll check grads again already did 2x.

If I have a weight distribution hitch the tongue weight should be minimal right? I really don't want to go king because 99% of the time it's just me in the vehicle without aftermarket weight and I don't want to compromise ride quality if I don't have to.

I have no idea how the weight distributing hitches work so I can't help there. Agreed on King being potential overkill. I would take the time to get a good set of measurements in your common driving load out and then a set with your trailer loaded up. See how close you are to straddling the neutral spec and adjust as needed.

 

[ramangain]

Just add rear airbags and inflate as necessary.

 

[suprarx7nut]

Just add rear airbags and inflate as necessary.

I feel dumb having forgotten about airbags. Perfect use case for those. Thanks.

 

[ramangain]

I feel dumb having forgotten about airbags. Perfect use case for those. Thanks.

"Some days you eat the bear, and some days the bear eats you."

 

[Dref]

I have been reading this post like a bestselling novel. Excellent report of the issue and awesome team work to solve the problem. This is definitely a reference for me as I go through the same motions. I was about to change my globes but I will go through the bleed process and see what happens. I’m always amazed when I find an answer on Mud which relates to my specific problems especially dealing with AHC. Thanks for all the info.

 

[Muhammad Rais]

What is utility bleed? Everyone is talking about it but I can’t find what does it mean.

stop bleeding manually and use the utility bleed your were going in the right direction.

 

[Muhammad Rais]

Seems like a combination of actual bleeding and air bleeding/utility bleeding. Only getting 10+ sometimes often high 8s to 9s it takes much longer to get up from those lower numbers.

after I did a fluid flush and after drove 100 miles my car was parked at home fine. I started to drive out then all of a sudden front went down and back stayed fine. Car wouldn’t go to H or L. Stays in N and also flash off. After reading all these I am thinking air or bad pump assembly but I am nervous. With all these messages I am lost again where to start. Since I bought the car I am trying my best with maintenance but it’s always one after another.
Can one of you expert explain each process?
1. Actual bleeding
2. Air bleeding
3. Utility bleeding
I am in Houston and my tech stream is not working. Found one Facebook member locally from 100 & LX470 group who will meet me to help out with tech stream. Thank you guys for all your knowledge.

 

[Muhammad Rais]

FIXED! Blead 8 oz from accumulator and at the corners to the bump stops from n with truck off. I'm getting changes under 20 seconds and spec accumulator pressures. Tomorrow I'll carefully flush the system with fresh fluid. Last pic is the fluid I started with before this adventure began. Grads now at 9.

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FIXED! Blead 8 oz from accumulator and at the corners to the bump stops from n with truck off. I'm getting changes under 20 seconds and spec accumulator pressures. Tomorrow I'll carefully flush the system with fresh fluid. Last pic is the fluid I started with before this adventure began. Grads now at 9.

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You mentioned you kept the truck in N and turned off the car then you bleed them.
When I did my flush, 1st I put it to Low then turned off the car. Then I started to bleed.

 

[suprarx7nut]

You mentioned you kept the truck in N and turned off the car then you bleed them.
When I did my flush, 1st I put it to Low then turned off the car. Then I started to bleed.

I think you're getting lost in the details on bleeding. It's all doing the same thing - moving fluid out of a bleeder and hopefully into a clear tube.

1. Manually - put the car in N or L (I always use L), turn off. Then crack open a bleeder and care not to crush yourself.
2. Techstream - Use the utility to force the pump to just run. I can't recall if there's a separate bleed utility or if it's just a part of the pump active test.

Either way, observe the fluid coming out into a clean clear tube. It should be perfectly fluid with zero bubbles. Any bubbles present means you need to keep bleeding.

 

[Muhammad Rais]

I think you're getting lost in the details on bleeding. It's all doing the same thing - moving fluid out of a bleeder and hopefully into a clear tube.

1. Manually - put the car in N or L (I always use L), turn off. Then crack open a bleeder and care not to crush yourself.
2. Techstream - Use the utility to force the pump to just run. I can't recall if there's a separate bleed utility or if it's just a part of the pump active test.

Either way, observe the fluid coming out into a clean clear tube. It should be perfectly fluid with zero bubbles. Any bubbles present means you need to keep bleeding.

When I bleed to get rid of the air, is there any order that I have to follow. I mean 1st accumulator then globes or video versa? Once I am back in town I will post a video.

 

[Dref]

When I bleed to get rid of the air, is there any order that I have to follow. I mean 1st accumulator then globes or video versa? Once I am back in town I will post a video

I went through the fluid flush and appeared to have the same symptoms as you: stuck in N. Off flashing.

To put it short, I believe the movement of fluid agitated some old particles/debris in the system and it clogged up my pump sub assembly. I swapped it out with a used one from AHC parts from someone deleting the system. Maybe it could have just used a cleaning. But after that, everything was working great. I will bleed the system again and I expect the ride to be even better.

You definitely need techstream or something to read neutral pressures.
I changed out all my sensors (from someone else’s AHC delete), added King springs to the back, and installed new globes (~$650 from Impex). I’m happy and it wasn’t as expensive or difficult as I thought. Gathered the info from Mud. Most shops don’t know anything about AHC so you are better off DIYing.

I bled the accumulator first then the globes LF, LR, RF, RR. Have extra fresh fluid on hand. But in a pinch, I recycled the new fluid back in. Some might suggest not to, but I was waiting for new fluid and I had to get the truck back on the road.

A lot of info and it gets confusing sometimes. But I’ve had dramatic results. And I’m an idiot mechanic.
You’ll get it going.

 

[Muhammad Rais]

I went through the fluid flush and appeared to have the same symptoms as you: stuck in N. Off flashing.

To put it short, I believe the movement of fluid agitated some old particles/debris in the system and it clogged up my pump sub assembly. I swapped it out with a used one from AHC parts from someone deleting the system. Maybe it could have just used a cleaning. But after that, everything was working great. I will bleed the system again and I expect the ride to be even better.

You definitely need techstream or something to read neutral pressures.
I changed out all my sensors (from someone else’s AHC delete), added King springs to the back, and installed new globes (~$650 from Impex). I’m happy and it wasn’t as expensive or difficult as I thought. Gathered the info from Mud. Most shops don’t know anything about AHC so you are better off DIYing.

I bled the accumulator first then the globes LF, LR, RF, RR. Have extra fresh fluid on hand. But in a pinch, I recycled the new fluid back in. Some might suggest not to, but I was waiting for new fluid and I had to get the truck back on the road.

A lot of info and it gets confusing sometimes. But I’ve had dramatic results. And I’m an idiot mechanic.
You’ll get it going.

Thank you so much. Going to meet another member on Sunday who will help me with tech stream. Let’s see from there. I will keep you guys posted.

 

[Dref]

How was the car driving before you did the flush? I had a bouncy ride which was also jaw rattling over bumps and potholes.

 

[Muhammad Rais]

How was the car driving before you did the flush? I had a bouncy ride which was also jaw rattling over bumps and potholes.

Car was driving fine. Few months ago another member @IndroCruise helped me out guided me to tackle the pressure and everything was by the spec. I needed a flush since I bought the vehicle. So I decided to change it and then drive normal for 100 miles. Then all of a sudden front of the vehicle went down and rear stayed same. Sunday or Monday I will get access to tech stream and then go from there.

 

[katit]

There is couple discussions in 200 forum about issues after ahc flush.

there is a batch of bad AHC fluid being sold by dealers. Fluid has some contamination gello like stuff plugging pumps and filters

 

[uHu]

There is couple discussions in 200 forum about issues after ahc flush.

there is a batch of bad AHC fluid being sold by dealers. Fluid has some contamination gello like stuff plugging pumps and filters

 

[suprarx7nut]

I wasn't aware the fluid from dealers was the cause, but yes, multiple people have talked about/posted pictures of a gelatinous substance blocking the screens within the 200 series AHC pump. Seems like that might need to be a first check when the 200 pump doesn't seem to want to prime/flow.

 

[IndroCruise]

There is couple discussions in 200 forum about issues after ahc flush.

there is a batch of bad AHC fluid being sold by dealers. Fluid has some contamination gello like stuff plugging pumps and filters

Some pictures of the problematic internal strainers/screens (not to be confused with the strainer at the AHC Tank) are found in #Post 70 in this thread:

AHC pump out? With code 1762

I have seen 1.x was able to program key, customize telescoping, door lock, window and sunroof settings. The 1.x cable I own was able to program my key, disable my DRLs, and stop that annoying auto-telescope wheel from activating. I have a 01LX that doesn't have TPMS, and I have read multiple...

forum.ih8mud.com

Go back to Post #69 in the same thread for further pictures of the pump internals and also a diagram and description of the nature of the pump taken from the FSM.

Previously, @PADDO made observations at Posts #16 and #19 in a different thread:

AHC help needed

I hooked my 2002 LX470 with 80K miles up to techstream yesterday to see what my neutral pressure readings were after replacing my globes. I was only getting like 6 graduations from the old globes and my front suspension felt like it was stuck in sport mode. After replacing the globes I have...

forum.ih8mud.com

He noted that:

“The two screens are internal to the pump so the pump/reservoir assembly needs to be removed from the vehicle. It’s then a matter of taking off the circular external pump housing which gives access to the pump. It’s retained to the main body and held together, its a sandwich design, by four cap screws. Undo the screws, and disassemble the pump sandwich and the screens are revealed. They are pressed in and can be cleaned in situ with a blast of 100% hydrocarbon cleaner or you can back them out with a pick to clean. Reassemble, install the pump/reservoir fill with fluid and let it sit for a while to assist the fluid in working it’s way into the pump housing/intake and fire it up. If it times out because it’s airlocked and can’t prime then force run it manually*”.

* means operation of the pump by “Active Test” for about 10 seconds with AHC fluid at correct level or better in the tank, or operation by direct connection to the battery.

Note that the strainers/screens are located on the input and output sides of the tiny gears (smaller than a thumbnail) which provide the actual pumping action. Gear pumps usually are specified for high pressure / low volume applications where the fluid is free of particulates. The strainers/screens are intended to keep particulates out of the actual pump. Particulates might otherwise degrade or destroy the gear action.

When an AHC Pump is thought to have failed or a relevant DTC such as C1762 is recorded – meaning that pump has power at the motor and rotates but the pressure is weak and AHC response is slow – then this is more likely to be caused by clogged strainers/screens than problems in the actual pump, unless the screens are missing or have holes which allow particles to pass into the gears. The pump is small but fit for purpose -- it would take something like a stream of sand to destroy the pump.

It is a judgement call whether to disassemble the actual pump and inspect and clean as described by @PADDO, or, replace the pump sub-unit (Part Number 48901-60010 – current Partsouq price USD165.31 plus delivery). For peace of mind, replacing the pump sub-unit every 15 to 20 years may not be such a bad idea – especially where long term neglect (infrequent AHC fluid changes and infrequent AHC pressure checks) by previous owners is suspected. If using a secondhand pump, suggest disassemble and clean the strainers/screens before installation of the pump in the vehicle.

Unless it is desired to renew other associated components or unless there is a very conservative view about reliability, it should not be necessary to replace the whole assembly consisting of pump/motor/tank/pressure sensor/temperature sensor/housing with Return Valve, etc (Part Number 48910-60012 – current Partsouq price USD1,237.34 plus delivery).

Suggest if disassembling the pump to clean the internal screens/strainers, either leave the tiny gears and their carriers in place, or, carefully mark and photograph their orientation to one another so that they can go back together with all parts in the same place and gears meshing in exactly the same way. Ideally, replace all o-rings encountered and also the oil seal between the pump and the motor.

Step by step guidance with pictures on removal of the pump assembly can be found here:

AHC pump removal with pics

This is an attempt to explain how I removed and replaced the AHC pump with a few pictures to help. Tools needed are... --10 mm deep socket (for bolt under reservoir) --10mm wrench --10mm crowfoot or small 10mm ratchet would be gold for other bolt holding reservoir --fluid extractor hose and...

forum.ih8mud.com

There are extensive but confusing discussions on IH8MUD “200 series Cruisers” concerning possible problems with some AHC Fluid supplies in USA but not sure whether the problem is real. In 2020 and 2021, I have bought genuine Toyota/Lexus AHC Fluid in 2.5 litre drums from Australian Toyota/Lexus dealers (fluid made by Japanese oil company Idemitsu Kosan Co., Ltd) and not had any problems. Suggest check information with local dealers about whether there is fake supply in circulation and insist on receiving the genuine stuff, no substitutes.