AHC Purging Question

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2007 LX, undercoated, and some of the ACH bleed valves do not have the rubber covers so there is some coating over them. I'm wondering if I will be able to drain them/if the little hole is plugged up. Can I run a small wire up in there to clean it out, or will loosening the lock nut allow fluid to flow anyway? I was thinking about using a dremel with light wire copper brush to clean up these nipples beforehand. Am I thinking clearly on this project?
 

suprarx7nut

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2007 LX, undercoated, and some of the ACH bleed valves do not have the rubber covers so there is some coating over them. I'm wondering if I will be able to drain them/if the little hole is plugged up. Can I run a small wire up in there to clean it out, or will loosening the lock nut allow fluid to flow anyway? I was thinking about using a dremel with light wire copper brush to clean up these nipples beforehand. Am I thinking clearly on this project?
You're on the right track with the dremel tool. I would try to remove the undercoating with as little abrasion as possible. Wire wheel is a good start.

It's important to have a good hose seal when bleeding that fluid so you don't want to gouge/sand it much more than needed.

When you next do a full flush or change out a globe, I would replace the bleed screws with new rubber caps as well.
 
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Thanks for the help. I'm really hoping that I can perform the purge, and that they are not corroded or plugged up where I can't drain the fluid. If I can get it purged I'll definitely change out the plugs/rubber covers. I'll soak them with Kroil penetrating oil for a while before I try to twist them I guess and keep fingers crossed.
 
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2007 LX, undercoated, and some of the ACH bleed valves do not have the rubber covers so there is some coating over them. I'm wondering if I will be able to drain them/if the little hole is plugged up. Can I run a small wire up in there to clean it out, or will loosening the lock nut allow fluid to flow anyway? I was thinking about using a dremel with light wire copper brush to clean up these nipples beforehand. Am I thinking clearly on this project?

Suggest before starting, buy five (5) bleeder valve from a nearby Toyota or Lexus dealer -- see pics and Part Numbers below. These cost only a few dollars and it is worthwhile to change the bleeders anyway. Then you can look at them and get a clear idea about them.

Then source some AHC Fluid – but as @planomateo mentions, there have been multiple reports on IH8MUD “100 series” forum and on IH8MUD “200 series” forum relating to new AHC Fluid containing a build-up of a gelatinous material which definitely is not wanted and may have caused blockages in AHC Pumps and elsewhere.

The AHC Fluid supplied in the USA mostly seems to come in a 1 litre plastic bottle (Part No 08886-81221) and this supply seems to be implicated in the reports in both forums – the “Search” function should reveal all.

In other parts of the world (Australia and elsewhere) AHC Fluid is supplied in 2.5 litre steel drums (Part No 08886-01805) which I have bought frequently and used without problems. Sometimes this seems to be available in USA, sometimes not, and sometimes people report importing the AHC Fluid themselves in steel drums, such as from PartSouq Auto Parts Around the World - https://partsouq.com/ or other overseas supplier.

Whatever, only genuine AHC Fluid should be put in the AHC system – otherwise internal damage to membranes, seals etc is inevitable. If a mechanic suggests using an alternative fluid in the AHC system, find another mechanic.

Personal habits vary – I never start a bleeding effort without at least 5 litres of AHC Fluid (two drums) on hand, even though it may not all be used in one effort. If change-out of ‘globes’ or other parts are involved, I would have 7.5 litres (three drums) on hand at the start. Unused fluid can be re-sealed to keep moisture and air out and go back on the garage shelf. I prefer not to re-use fluid which has passed through the system and picked up detritus along the way; others are happy to do so. The Owner’s Manual says change out AHC Fluid each 6 years or 60,000 miles – a more cautious approach would be a fluid change each 3 years or 30,000 miles. It is not difficult, AHC Fluid is not so expensive and clean fluid help prolong functional life of the AHC system (provided that AHC pressures also are managed and kept within the ranges specified in the Factory Service Manual).

You might consider pressing the Parts person at a Toyota or Lexus dealership for information about the reported problems in new AHC Fluid and whether it has been resolved in USA -- and reporting what you learn. It is all a bit surprising – the same AHC Fluid is used worldwide in AHC systems in LC100 (where fitted), in LX470, in LX570 and presumably in the LX600 successor. The same fluid also is used in the KDSS suspension (where fitted) on LC200 and in the e-KDSS system in premium LC300 models. It is incomprehensible that dud AHC Fluid is being sold.

In any case, given the reports it is suggested that the new AHC Fluid be decanted into a very clean transparent glass container and inspected with a light behind and then filtered, just to be reassured of clean fluid condition.

As @suprarx7nut mentions, be careful with the dremel. When bleeding, a tight fit between bleeder and bleeding hose saves a lot of mess. A good fit between the bleeder and a good quality six-sided (not multipoint) 10mm ring wrench is important for flow control and to avoid ‘rounding’ the hexagon on the bleeder.

If the bleeders are too blocked to prevent fluid exiting, consider placing a groundsheet or oil-soaking carpet on the floor below and very gently opening the bleeder a few degrees at time until fluid flows around the thread. This does make a mess but that can be cleaned later. When fluid flow stops, replace the bleeder.

Always wear eye protection when bleeding and be aware that the vehicle body will drop quickly when AHC pressure is released – keep head and body clear.

Yes – it is worthwhile to give bleeders a good soak with your preferred thread penetrating oil once or twice several days before starting – although it is unclear whether this will penetrate the mentioned undercoat.

AHC Bleeder Valve.jpg


Bleeder Valve.jpg
 
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Great information. I have sourced and ordered these valves and rubber covers from McGeorge Toyota, as well as the 2.5L can from them as well. I appreciate the tips. I will be careful with the Dremel (using light wire copper brush). My intent is just to clean up the nipples so I can get a good seal and hopefully the penetrating oil will allow movement and purging. My AHC system works well, and my main concern with completely swapping out the purging valves was introducing air into the system. This may not be the way it works (I don't know, my first time at this).

As always, I appreciate the help. This is a great place to learn.
 
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Great information. I have sourced and ordered these valves and rubber covers from McGeorge Toyota, as well as the 2.5L can from them as well. I appreciate the tips. I will be careful with the Dremel (using light wire copper brush). My intent is just to clean up the nipples so I can get a good seal and hopefully the penetrating oil will allow movement and purging. My AHC system works well, and my main concern with completely swapping out the purging valves was introducing air into the system. This may not be the way it works (I don't know, my first time at this).

As always, I appreciate the help. This is a great place to learn.

The exchange at Posts #33 and #34 at this thread provide some input from longtime AHC guru @PADDO which may provide some comfort concerning changing bleeders.

For what it is worth I can say that I also have done it this way and it worked fine.

That said, it is far better that you proceed in line with your own instincts and precautions, especially in early learn-by-doing efforts. Different approaches can be tried later.

Whatever choice you make, hope all goes well -- a 2007 LX470 is a venerable machine, and the AHC/TEMS systems are well worth preserving!!
 
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Thanks for pointing me to that thread Indro. It gives me even more direction and peace of mind. Much appreciated.
 
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So I've got a question, likely a stupid one but here goes.....

I have not changed the fluid out yet, but I can purge the actuator and drivers sides accumulator's, but I cannot get the rear accumulator valves to budge (haven't gotten rough with them yet, but don't want to break them off). Under these circumstances Is it worth the effort to go ahead and change/purge out as much fluid as possible ? Will I accomplish anything by proceeding?
 

suprarx7nut

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So I've got a question, likely a stupid one but here goes.....

I have not changed the fluid out yet, but I can purge the actuator and drivers sides accumulator's, but I cannot get the rear accumulator valves to budge (haven't gotten rough with them yet, but don't want to break them off). Under these circumstances Is it worth the effort to go ahead and change/purge out as much fluid as possible ? Will I accomplish anything by proceeding?
If it were me, I'd work on getting those frozen screws out. Lots of penetrating oil. Some careful heat. Many cycles of this. If it breaks off, you're exactly where you'd be if you left it in there. 🤷

Old fluid isn't helping anything in there. Getting as much fluid changed out is a good thing. I expect the fluid will all mix over time, so bleeding out of one or two points has the potential to do the job of a proper bleed at all points - it's just not very efficient with your time and energy because you'll need to flush in many sessions with time in between each to allow the fluid to move around a bit.
 
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You can just flush RH side rear globe for now.

If left side rear globe bleeder will not open. Either side gets job done. Same for fronts. If we flush one side, nothing but a drop or 2 comes out other. If we flush one side, fill, charge and flush other side. Clean AHC fluid comes out other side already. So we don't typical flush both side, as it just waste the liquid gold (Toy AHC fluid).

Although when changing all globes, I do bleed all globes of air. In fact not a bad Idea to re-bleed, even flush again soon. As some air bubbles tend to remain.

The accumulators bleed, is the one breaks the most often. Like any bleeder, they need to be kept capped (rubber cap). The accumulator's bleeder points with open forward. So water and debris form tire, gets in bleeder easily. It is also a thinner walled bleeder, so not as strong as others. When it breaks we must either repair, or just flush around it. So some old fluid from it, can not be gotten to. But even if all bleeders working well, we don't get all. Shocks and some small amounts throughout system always remains. But by flushing, than using actively over time. Than re-flushing often, we get mixed in and flushed as good as we can.

BTW: I've induction coil for heating up frozen bolts and nuts, works good! They're also a safer way than open flame, to heat bleeders.
 
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I appreciate the info, and understand about bleeding one side only. Problem is, neither the LH or RH rears will bleed because I can't get them open. I may just proceed with the "get them as good as I can" attitude for now anyway.
 
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Many AHC systems have been removed for LX470 & 06-07 LCs. So many in mud have the globes with housing/bracket lying around.. Swapping may be easiest solution.;)
 
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So I've got a question, likely a stupid one but here goes.....

I have not changed the fluid out yet, but I can purge the actuator and drivers sides accumulator's, but I cannot get the rear accumulator valves to budge (haven't gotten rough with them yet, but don't want to break them off). Under these circumstances Is it worth the effort to go ahead and change/purge out as much fluid as possible ? Will I accomplish anything by proceeding?

Mostly agree with posts by @suprarx7nut and @2001LC.

Here are some further notes which may help .....

Frozen bleeders in the AHC system (or the brake system) are a PITA!!

As a preliminary, if you have not already read the attached “AHC/TEMS General Description” may I strongly suggest doing so. This document helps gain an understanding of how these two systems are meant to work. For those of us who are impatient readers, it pays to print the document (20 pages). In my case, I found that I skipped through it far too quickly – and on the second or third re-read (and subsequently!) I picked up details and a better understanding which I missed the first time.

If you don’t have access to a hardcopy Factory Service Manual, then the documents found at LC100 Workshop Manual - https://lc100e.github.io/ suffice for most mechanical and electrical maintenance and diagnostic purposes on both LC100 and LX470. This reference also includes fitting and diagnostic sections on AHC/TEMS systems and components – these are the same on both vehicle types (where fitted in the case of LC100). A scanning tool, preferably Techstream, which can read the AHC Electronic Control Unit (ECU), is essential for diagnosing AHC conditions and reading and adjusting AHC pressures. There are the obvious body differences and additional ‘luxury’ fittings on LX470.

As I understand it, you have a 2007 LX470 with relatively low miles and generally in good condition. A previous Owner has treated the under-body with an anti-rust film – it is not clear whether the main motivation was rust prevention or rust concealment. Whatever, this stuff has smothered the AHC apparatus everywhere along the chassis.

This vehicle is one of the last of the breed. Unless it is badly infected with pervasive under-body rust, it is well worth a lot of effort to preserve it. The AHC and TEMS systems, unloved by many, are relatively simple systems. Like any electro-hydraulic system, they do need basic maintenance and good hydraulic hygiene. This is easy do-it-yourself stuff and not onerous but sadly, it is often neglected – even by dealer workshops, for some of whom basic hydraulics and diagnostics seem to be a foreign language! Happily, AHC and TEMS are neither difficult nor expensive to resuscitate after neglect, provided the systems basically are intact, not rusted out and not electrically demolished – and provided the Owner actually has a will to resuscitate them.

You have stuck bleeders at the Left Rear and Right Rear Damping Force Control Actuators (to which the ‘globes’ are attached) and also a stuck bleeder at the Height Control Accumulator mid-way along the Left chassis rail.

When the vehicle is at rest or with steering straight ahead, the Rear Gate Valve within the Control Valve Assembly is open and the Left Rear and Right Rear Damping Force Control Actuators are interconnected at the same pressure. If you could open only one of the Rear bleeders, you could bleed the Rear AHC system -- but not perfectly. The same applies at the Left Front and Right Front. The Front and Rear are not connected in this way. Bleeding at the Front bleeders does not help you at the Rear.

When raising the vehicle, the Front and Rear Levelling Valves in the Control Valve Assembly open and close in a sequence determined by the ECU and the vehicle shuffles upwards, using fluid pressure and flow firstly from the Height Control Accumulator (this is its only purpose in life) and secondly from the AHC Pump as necessary.

When lowering the vehicle, the Front and Rear Levelling Valves open, the Return Valve in the AHC Pump assembly remains closed and AHC Fluid from all four 'Shock Absorbers' and all four 'globes' returns directly to the AHC Tank. (If the 'globes' are in poor condition -- worn out -- with low remaining nitrogen pressure, then not much fluid will be pushed by the low nitrogen pressure behind the membranes in the the 'globes' back to the AHC Tank).

In this way, dropping the vehicle to "LO" height, evacuating the AHC Fluid from the tank, re-filling the AHC Tank with new fluid, then raising the vehicle to "N" or "HI", would result in new fluid being sent to all four 'shock absorbers' and all four 'globes', and to refill the Height Control Accumulator at the end of the raise.

Repeating this process over and over and over would eventually dilute the old fluid and replace most of it. It would be an imperfect process, especially if the 'globes' are old and in poor condition because there will be limited flow in and out of the 'globes', some fluid remains trapped in the 'shock absorbers' anyway and it will require a lot of repetition and a lot of fluid to make any progress. The attached "HI-LO Test" can be used to give an idea of overall 'globe' condition -- but actually the test only is comparable with the FSM numbers if it is performed with Front and Rear AHC pressures within the FSM-prescribed range.

Back to the bleeders -- which look like this:

Bleeder Screw Xsection.jpg


Over time, an uncapped bleeder is surrounded by, and filled with, water and dirt and whatever else is thrown up from the road. Rust will seep down the thread from the top and also may work its way up the thread from the bottom (because the passageway is open to atmosphere).

In addition, the bleeder may have been over-tightened by the person who last used it. Repetitive over-tightening damages the seat which the closed bleeder is meant to block, which encourages leakage, which encourages more over-tightening, and so it goes on and it all gets worse. The FSM-specified bleeder tightening torque is only 73 inch-pounds (same as about 6 foot-pounds) at the Actuator. This really is only a gentle nip with a short-handled wrench, sufficient to avoid leakage if all is in good condition, does not need a heavy hand.

In your situation, I would do the following, starting with bleeders and their receiving Actuators and Accumulator still in place on the vehicle:

1. Using fingers only, turn a twist drill of similar diameter inside the bleeder aperture. The idea is only to clean out any debris in there and hopefully clear the small side hole at the bottom of the bleeder. Flush the aperture with penetrating fluid of choice, preferably inserting a small diameter straw into the bleeder,

2. Using a sharp pick, clean around the bleeder thread and attempt to scratch open a passage where the bleeder thread enters the Actuator or Accumulator. Flush with penetrating fluid of choice,

3. Leave for 24 hours, then repeat steps (1) and (2). The next steps rely on vibration – they may or may not work but are worth a try before attempting anything more drastic,

4. Apply a good quality tight 10 mm six-point wrench (six-sided hexagonal, not a 12-point and definitely not an open wrench) to the bleeder (or a six-point socket and a small drive). A good fit on the bleeder is important to prevent rounding. Don’t worry about the bleed tube just yet. The first task is to loosen the bleeder screw. If there is any leakage, that will be counted as a success – and clean-up is easy!

5. If the bleeder already is rounded, you may need to dress it lightly, or buy a special socket – Google for “remove rounded bolt”,

6. Hold the wrench in place and tap it firmly (but not harshly) and repetitively with a small hammer, to induce the wrench to turn the bleeder counter-clock wise (the opening direction),

7. Do the same in the opposite direction, as though turning the bleeder clockwise. (Seems counter-intuitive but stay with it),

8. Repeat these cycles over and over and over again, with a lot of patience. In between, apply firm but not heavy hand pressure on the wrench and the bleeder, also in both directions,

9. The aim is break the rust bonds between the thread of the bleeder and the thread in the Actuator or Accumulator by a combination of vibration from hammering and torsion from hand pressure – patiently, firmly, repetitively but not too heavy-handed, as the aim is to cause movement with out shearing the bleeder with too much strength,

10. If the effort succeeds, attach bleed hose and release pressure and fluid,

11. Immediately replace old bleeders with new bleeders, and then complete the bleeding procedure. Forget the following steps (12) to (20) which success has made unnecessary!!

12. If the above effort fails, or if the bleeder does break, then the ongoing procedure will be much more drastic. As will become obvious, this will be quite disruptive and may as well wait until you are ready to replace the set of four ‘globes’ (which also seems likely to be in your near future unless there is a record of recent ‘globe’ replacement),

13. Each relevant Damping Force Control Actuator will need to be removed from the vehicle – AFTER relieving the system pressure by loosening the pipes entering Actuator. This will be messy, so first prepare the floor for easy clean-up later – and ALWAYS wear good quality industrial-grade eye protection when doing this kind of work on hydraulic components,

14. With the Actuator off the vehicle and held in a vice, use the hole in the broken bleeder as a pilot, and drill a hole through the bleeder large enough to accommodate a suitably sized Ezi-Out, but not so large as to damage the thread in the Actuator,

15. Check a few Youtube videos and websites on "How to use an Ezi-Out to remove a broken bolt",

16. Check some of the many Youtube videos on “How to remove a broken brake bleeder” for some very similar procedures. Some of these methods suggest applying a hot flame to assist the task. Certainly, NEVER do this while lying under or alongside the vehicle, and NEVER do this to the Height Control Accumulator unless its very high contained pressure has been relieved. This requires manual operation of the solenoid valve at the front of the Height Control Accumulator, which is quite a tricky step. I have to say that personally I am too conservative to have the courage to apply flame to ANY of the AHC bleeders or components – seems potentially unsafe, and also risky given the intricate valves and components inside. However, other knowledgeable people at IH8MUD may know better from their experience. Also see link further below about removal of the Height Control Accumulator,

17. When ready, apply more penetrating oil and apply the Ezi-Out to the task,

18. If all of the above fails, then it is time to find replacements -- new or used -- of the Damping Force Control Actuators and the Height Control Accumulator with working bleeders – in the same way as brake calipers would have to be replaced if all efforts failed to remove the bleeder,

19. As always, cast around IH8MUD and other forums for alternative ideas and inputs,

20. Hopefully the notes at this link on Removal of Height Control Accumulator and the following posts in that thread are not required!

Hope all goes well! Please let us all know how it all works out – the problems and frustrations of stuck bleeders are not unusual and many others will be interested.
 

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Joined
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Thank you so much for the most informative post. I'll try some of those tricks on the purge valves. Just to be clear, I can purge the fronts and the accuator, just not the rears. I want to save the AHC, as the ride is butter smooth. I like it alot.
 
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Bleeder rubber cap on all 5 bleeders of AHC and all 4 bleeders on brake calipers, are so important.

Even when all bleeders of AHC system will open. We don't get it all old fluid out, during a flush. Some old fluid always remains in system, mostly in the shocks. But by flushing often and using AHC at different setting as we drive around, it mixes new with old fluid deep into shocks.

You can flush fronts, with only one front bleeder working/opening. Which with just one bleeder opened, flushes both sides of front circuit. Same holds true of rear circuit, if just one rear bleeder working.

Even if only one bleeder of the 5 in the AHC system opens. You can flush, it repeatedly over time, it will help refresh most all fluid.

Even if no bleeder opens, you can flush.
By lowering and raising to high repeatedly, and repeatedly draining & filling reservoir to keep dilution old mix in reservoir with new fluid. You can flush the system. It just not as effective. It will mix new and old fluid as you drive and actively lower/raise and run it in sport to comfort settings (comfort moves more from shocks). Which mixes fluid, refreshing more and more with each drain & fill of reservoir. It's just not as effective, nor does it remove as much or any of the particles from shocks, lines, globes accumulator, gate valve. Some fluid, deeper in system (furthest from reservoir) will not much if at all.

I'll add: One of those "I beat the drums" on!
Bleeder rubber cap on all 5 bleeders of AHC and all 4 bleeders on brake calipers, are so important. Not only do bleeders get frozen in, without them on. But the rust, can damage seat bleeder seat-in/seals-point of component. Then we have a much bigger cost, as housing of globes, accumulator and or brake calipers will need replacing. Ton of cost and headache, just because a $2 rubber cap not on a bleeder.


I know why owners don't make sure bleeder caps are on, they don't know!
So why don't all shops cap bleeders:
For some it's their MBA (more business assured):bounce2::rofl:$$$$$ .
For some it's laziness.
For some it's incompetence.
For some it's IDC (I don't care).
 

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