AHC pump removal with pics (1 Viewer)

[BullElk]

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 container
--3-4 liters of AHC fluid (for one flush)
--Turkey baster

1. Begin by.... If you have a choice in the matter, which I didn't, lower truck to L position forcing fluid into reservoir. Then use turkey baster to remove as much fluid as possible from
reservoir.

2. Use fluid extractor hose and 10 mm wrench to bleed out globes and release pressure in system. Very little came out due to most of it in reservoir. Extractor hose I use is from Autozone for $14.99 and hooks nicely on fitting. It also has a heavier pliable rubber hose to lay where you want it.

3. I thought it was best to then remove reservoir making it easier to reach bolts. Two bolts hold the reservoir in place.

The top right screw is where a 10mm crowfoot or small ratchet wrench will help you ooze with positive feelings.

4. Unplug the three connectors... Power plug, temperature sensor and pressure sensor

 

[BullElk]

5. Remove 10mm bolt to take off bracket holding steel fluid line. Then remove steel line.

6. Remove the motor and pump by removing two nuts and one bolt (I think that's correct) Bolt is underneath the pressure switch. The two nuts are on opposite side sitting under the reservoir.....hence removing reservoir first.

Pump should lift right off. That should be about it for removal. Then replace new to you and working pump in reverse order. Replace Reservoir, Fill with about 2.5-3 liters of fluid. Start LX and try your best to hear the motor raise your ride. It ain't easy. It sounds very similar to a hydraulic Swiss watch. Press switch to raise to H forcing fluid in the lines. Bleed one front and one rear globe until good clean pink tasty fluid is visible. Tighten fittings and add more fluid to max mark. DONE.

 

[ramangain]

Tasty?

 

[nukegoat]

Tasty?

It's not. I got some in my mouth. It is gross

 

[l3n0x]

Or just remove the 3 bolts holding the bracket & the single AHC line & the electrical connectors and lift the whole assy out.

 

[BullElk]

Or just remove the 3 bolts holding the bracket & the single AHC line & the electrical connectors and lift the whole assy out.

Possible but like mentioned in another mudder thread, it appeared to me you would have to get above fender liner. And nice to have big fat reservoir out of the way.

 

[MongooseGA]

Nice write up.

Were you able to source a replacement pump? If not, I still need to pull mine out of my engine bay. I also have whatever that big cylindrical unit from the frame is.

 

[arkmm]

This was super helpful for removing my pump and reservoir last night. Thank you!!

 

[DBULL]

Excellent information! I plan to flush my system in the next few days and would like to remove the tank for cleaning.Any suggestions as to a solvent to remove stains inside of the tank?

 

[IndroCruise]

Excellent information! I plan to flush my system in the next few days and would like to remove the tank for cleaning.Any suggestions as to a solvent to remove stains inside of the tank?

On "solvent" for cleaning the AHC Tank etc, suggest use something similar as mentioned by @PADDO for cleaning the internal screens/strainers inside the Pump -- or at least that is what I have done:

Previously, @PADDO made observations at Posts #16 and #19 in the thread below:

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

At this post #19 in the above link, it is 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**”.

* in other words, something that dissolves oils and evaporates readily without leaving a residue, so not a detergent.

** 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 of the pump motor to the battery.

If a clean-up is being done, it is worth disassembly to investigate the screens/strainers which are are located inside the pump block, 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 screens/strainers 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 but the pressure is weak and AHC response is slow – then this is more likely to be caused by clogged screens/strainers 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.

Some more pictures of the Pump are found in Post #69 and 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

The problematic internal strainers/screens (not to be confused with the strainer at the AHC Tank) are shown at Post #70 in the above thread.

As can be seen in the diagram below from the FSM, the main purpose of the pump cover with the big "+" is to contain the pressure which is used to force the pump gears tightly onto the pump body so as to minimise side clearances and minimise fluid bypassing the gears at their sides. There won't be much flow in the space inside this cover but outside the actual pump. It is a natural trap for fluid.

As for many types of oils warmed and cooled over a long period of time in the presence of oxygen and moisture, a gel or sludge eventually will form in traps where fluid is stationary or moves slowly. Some of this gel or sludge may find its way into the pump. If so, it will be caught at the internal screens/strainers inside the pump, with loss of pump output pressure and flow.

So a clean-out is a good idea when there are suspicions about low pump pressure and flow and/or DTC C1762. A source of replacement internal screens/strainers is not known -- they do not appear on commonly available Toyota/Lexus parts diagrams and lists. It is not known which of the Toyota/Lexus suppliers is the actual manufacturer of the AHC Pump.

The screens/strainers could he eased out with a pick -- but carefully, do not want any holes in the mesh. A simple backwash may be a safer approach.

Alternatively, and 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 AHC pressure checks) by previous owners is suspected. The pump sub-unit is Part Number 48901-60010 – current price example: Partsouq: USD165.31 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 gears meshing in exactly the same way. Ideally, replace all o-rings encountered and also the oil seal between the pump and the motor.

Suggest if using a secondhand pump, disassemble and clean the screens/strainers before installing in the vehicle.

 

[medtro]

carefully mark and photograph their orientation to one another so that they can go back together with gears meshing in exactly the same way

Is this really necessary? What is the reason for this other than they can go back together with gears meshing in exactly the same way?

 

[IndroCruise]

Is this really necessary? What is the reason for this other than they can go back together with gears meshing in exactly the same way?

My suggestions in Post #10:

"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 gears meshing in exactly the same way. Ideally, replace all o-rings encountered and also the oil seal between the pump and the motor".
and
"Suggest if using a secondhand pump, disassemble and clean the screens/strainers before installing in the vehicle".

My earlier post may not have expressed my meaning well enough because more than meshing of gears is involved, so apologies offered for any misunderstandings or confusion caused.

For context, here is a picture of the way the parts of the of the overall AHC Pump assembly fit together and also shows the internal fluid flow within and around the the actual AHC Pump sub-assembly. No surprises here for anybody who has removed and disassembled the overall AHC Pump-Motor-Tank assembly after lifting it out of the vehicle:

The next step of disassembling the actual AHC Pump sub-assembly 48901-60010 is straightforward -- just remove four (4) screws -- but this is not well covered in the Factory Service Manual, so my pics and explanations are offered to assist.

The AHC Pump itself is a simple gear pump but even so, reassembly of this AHC Pump sub-assembly requires attention to detail. This is why taking step-by-step pictures is recommended for first-timers.

The important point is that the "notch" in one of the gearcases must be correctly located below the relevant strainer as explained in my notes attached to the pic below. If this is done incorrectly, resulting in the "notch" facing the wrong side of the housing, then the AHC Pump will not and cannot work correctly.

Maybe we are meant to 'interpret' this from the only description of the internal working of the AHC Pump sub-assembly to be found in the Factory Service Manual -- see below -- but, at least for me, it took a lot of staring at the diagram below while looking at a disassembled AHC Pump sub-assembly to work it out!

Here is another opinion from the IH8MUD "200 Forum" concerning the almost identical pump on LX570. @runnerxa at Post #28 advises:

HELP! AHC Pump Issue After Reservoir Drain/Refill - https://forum.ih8mud.com/threads/help-ahc-pump-issue-after-reservoir-drain-refill.1261668/page-2#post-14022130

“ ….you need to make sure you install the two small pump gear bearings back properly. There is a little notch on the two pump gear bearings and I believe they have to be pointed toward the inlet side. My AHC pump cavitation issue went away and the pressure was able to build quickly. It took me about two weeks of troubleshooting with Techstream and reassembling the AHC pump twice to figure out that I installed the pump gear bearings in reverse. So take a note of the original position when you disassemble the pump gears/bearings”.

Anyway, hope my notes above help to clarify ....

Personal view: The AHC Pump sub-assembly 48901-60010 will last a very long time but much less if AHC maintenance is neglected and if AHC Fluid is not changed at least as often as the Toyota/Lexus prescribed schedule -- and preferably twice as often for best longevity. If in doubt about AHC maintenance history on a 15 to 24 years old LC100/LX470 vehicle, suggest consider replacing the AHC Pump sub-assembly 48901-60010 (from Impex USD103.54; Partsouq USD173.49 -- plus freight on 0.435kg weight and plus taxes if any) as part of the base-line effort. Or at least disassemble and clean the internal strainers.

 

[medtro]

My earlier post may not have expressed my meaning well enough because more than meshing of gears is involved, so apologies offered for any misunderstandings or confusion caused.

Thanks for the reply. No need to apologize. My understanding is that the gear case with notch has to go to the correct slot (right slot in your picture), but gears meshing in exactly the same way is not necessary. That is the reason of my question. Please correct me if I am wrong.

 

[IndroCruise]

Something went wrong -- will re-post.

 

[IndroCruise]

Thanks for the reply. No need to apologize. My understanding is that the gear case with notch has to go to the correct slot (right slot in your picture), but gears meshing in exactly the same way is not necessary. That is the reason of my question. Please correct me if I am wrong.

Hi @medtro,

You have been around the AHC/TEMS systems and contributing to this forum for a long time and I am not about to tell you are ‘wrong’.

Simply said, my conservative view is to reassemble AHC Pump components in the manner that they were first assembled during pump manufacture and to use notes and photographs to help with this – and yes, this does assume correct assembly in the first place ….

However, this does not make you ‘wrong’ nor me ‘right’.

To my eye and obviously yours, the two AHC pump gears look identical. As I try to resurrect my very hazy memory of lessons long, long ago about gear design, the AHC pump gears appear to be manufactured as ‘simple’ involute spur gears – no helical twist, no undercut differentiating one side of the tooth profile from the other (as occurs in some industrial gear pump designs and which would make switching very unwise if it were possible).

So what is my hang-up about switching the slave gear to become the drive gear, swapping the gears from side to side, in an AHC Pump? (The position of the drive connection to the electric motor cannot be changed).

Basically, my hesitation is because switching also would switch the bearing surfaces of each tooth from one side of the tooth to the other side of the tooth as the gears rotate and mesh in the centre of the pump. Does that matter? I don’t know.

It means that the other side of the tooth would now be subject to wear and tear, pitting or whatever – and maybe this is a good thing, adds extra life?

It also may be that the new and old worn surfaces mean some changes to the geometry of the ‘trapped’ volume or fluid pockets between the gear teeth as the teeth pass through the centre of the pump. This might increase the bypass flow meant to escape via the “notch” through the axial clearances in the gearcases, through the designated filter, and back to the intake side of the pump. How significant is this? Will this add to cavitation and noise issues? Again I don’t know.

Too much over-thinking and too many “I don’t know’s”!!

So my conservatism suggests to me, “Just put it all back together like it was, or if in doubt replace the gears (which actually means replace the pump)” -- but that is just me -- others should do as they see fit.

The main issue to which I wanted to draw other readers’ attention in this and previous posts is to ensure that the “notch” is placed correctly, facing the inlet side of the pump. There can be no conjecture about that -- it is a “must do” for the reasons explained in the second and third attachments to my Post #12 in this thread. The AHC Pump cannot operate correctly without this pathway relieving the trapped high pressure fluid pockets between the teeth as the gears exit the mesh. If the “notch” is incorrectly placed, the AHC Pump may not operate at all or may operate very noisily, indicating cavitation. If buying a secondhand pump (not a good idea) suggest dismantle, inspect, clean internal strainers, check correct reassembly – before installation in the vehicle.

It is off-topic but the last point to mention is that unlike industrial gear pumps, there is no pressure relief valve protecting the AHC Pump and preventing it bursting in overpressure situations. Instead the protection adopted by the AHC Pump designers is for fast response times in the event of a fault per several pump or pressure related DTC’s:
C1718: 1 sec; C1762: 0.6 sec; C1763 and C1764: 0.3 sec.

 

[wilcoxoffroad]

What brand solvent did everyone use to clean the parts of the AHC components? I saw 100% hydrocarbon but wondering what I can buy locally that will do a good job. Thanks!