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

[ramangain]

You are getting a reasonable rear pressure. That hints to me the pump is probably OK.

You may want to try this: keep the tube accumulator valve open and put the tubing to catch the fluid in a big pan. Completely fill the reservoir with recycled fluid. Start the engine and let the AHC pump run until you get a few seconds of continuous fluid coming out of the accumulator. Close the valve, then shut off engine. Put drained fluid back into reservoir, then restart rig, let AHC run to try and repressurize, then try to perform L to N pressure test. Hopefully something registers for the tube accumulator pressure; nominally it may actually get to N.

 

[aharlan001]

You are getting a reasonable rear pressure. That hints to me the pump is probably OK.

You may want to try this: keep the tube accumulator valve open and put the tubing to catch the fluid in a big pan. Completely fill the reservoir with recycled fluid. Start the engine and let the AHC pump run until you get a few seconds of continuous fluid coming out of the accumulator. Close the valve, then shut off engine. Put drained fluid back into reservoir, then restart rig, let AHC run to try and repressurize, then try to perform L to N pressure test. Hopefully something registers for the tube accumulator pressure; nominally it may actually get to N.

Sounds reasonable, I will try in a few hours. For a bit earlier when it stayed in n pressures were reasonable at front and rear. Thanks so much for your help! Deep breath!

 

[uHu]

Just a comment on diagnosing pressures and pressure sensor:
Remember that there is only one pressure sensor on the system. There is no "Front press sensor", "Rear press sens" or "Accumulator pressure sensor"; it's all just readings from the pump pressure sensor which is done when the valve to the circuit in question is open (front, rear or acc). The reading that stays on the TechStream page is the one present just when the related valve closes. This is all software controlled, and the only time the readings make any sense, is when arriving at N height, coming from Lo. If you want to see real pressures in the system, you have to connect actual gauges to it. (Not that that is particularly useful in normal cases).

 

[suprarx7nut]

If you are occasionally getting up to N and back down, I think it might be air pockets in the system. cycling more and more might work them out, but a proper bleed is still my number 1 recommendation.

 

[aharlan001]

If you are occasionally getting up to N and back down, I think it might be air pockets in the system. cycling more and more might work them out, but a proper bleed is still my number 1 recommendation.

What do you mean by a proper blead? If you let me know the procedure I will gladly give it a try.

 

[aharlan001]

Just a comment on diagnosing pressures and pressure sensor:
Remember that there is only one pressure sensor on the system. There is no "Front press sensor", "Rear press sens" or "Accumulator pressure sensor"; it's all just readings from the pump pressure sensor which is done when the valve to the circuit in question is open (front, rear or acc). The reading that stays on the TechStream page is the one present just when the related valve closes. This is all software controlled, and the only time the readings make any sense, is when arriving at N height, coming from Lo. If you want to see real pressures in the system, you have to connect actual gauges to it. (Not that that is particularly useful in normal cases).

Intersesting... didn't know this, I guess this explains why despite a pressure of 7.2 or so in the height accumulator I am unable to blead anything from it!

 

[aharlan001]

You are getting a reasonable rear pressure. That hints to me the pump is probably OK.

You may want to try this: keep the tube accumulator valve open and put the tubing to catch the fluid in a big pan. Completely fill the reservoir with recycled fluid. Start the engine and let the AHC pump run until you get a few seconds of continuous fluid coming out of the accumulator. Close the valve, then shut off engine. Put drained fluid back into reservoir, then restart rig, let AHC run to try and repressurize, then try to perform L to N pressure test. Hopefully something registers for the tube accumulator pressure; nominally it may actually get to N.

I was really hopefull for this one. Initially when I cracked the bleader there was no flow. I started the car, still no flow. Techstream continued to show 0.0 for height accumulator pressure and a little pressure in the "front" (see initial techstream jpg). I closed the bleeder and a AHC reset by connecting the pins mentioned above and did the AHC air blead procedure with the buttons in the car and got an accumulator pressure on techstream (see final techstream). I then went back to the bleader and got a few mL out... so not much...

I'm sure the pump is running but it seems like pressure is not building in the height accumulator despite techstream pressures that say they are. So is the problem the pump assembly of the height accumulator. From what I have seen there are no reports of failed height accumulators only pumps...

 

[aharlan001]

What do you mean by a proper blead? If you let me know the procedure I will gladly give it a try.

Very very seldom do I get to n... I think only twice since this nightmare began. Typically when I hit up to N from L the light blinks for about 120 seconds as it is trying to go up and then when it fails the light stays lit at l... the only two times it has gone to N or stayed at N was after I messed with something, blead the system etc. I can't cycle back and forth between n and l... I did try doing so only letting n blink for 30-60 seconds before hitting the down button the truck did move a bit when I hit the down arrow. I did this cycle maybe 10 times but no change.

 

[LXKevin]

The accumulator pressure needs to be 10.2 ish. Mpa-g in neutral. Keep bleeding the system with the recycled fluid. Start the bleed at the height accumulator. Then one front till on the bumpstops then one rear till on the bumpstops. Check the reservior then start and up to neutral. Next time you get it back up to neutral take a pic of the data from techstream. Pressure data from techstream in low is basically useless as a uHu above said. Earlier you had decent front and rear pressure in neutral and the accumulator was 7ish if i recall. Keep bleeding

 

[suprarx7nut]

What do you mean by a proper blead? If you let me know the procedure I will gladly give it a try.

I mean bleeding out all 4 corners plus the accumulator. The Paddo method might call for that, but I'm not sure. Just make sure all the bleeders have been opened and plenty of fluid has had a chance to come out of each of those bleeders.

 

[ramangain]

I, too, am thinking you got air trapped in there. Frustrating, I know. I've had to chase air out before on my rig, but not to this extent.

May The Force be with you.

 

[ramangain]

I can share what worked for me. (Stop/start is engine below)

1. Begin in N (if you can) and fill the reservoir as high as it will go.
2. Open LR bleeder.
3. Start rig and ensure fluid comes out for 5 seconds. Close bleeder, stop rig. Recycle captured fluid into resevoir.
4. Repeat 2&3 on other 3 globes, then on accumulator.

This is how I fully chased air out on my rig. I had to do the full cycle 4-5 times IIRC. Your favorite music or podcast may help.

Due to this experience, I keep my fluid level in the reservoir about an inch above the plastic seam line when in N. If I ever run the reservoir dry in the event of going to H or even H+, it will be an Act of God and not my fault for not having enough fluid in the reservoir.

Edit: I'm not an AHC expert like other contributors to this thread, but I have obtained solutions to every problem I've encountered thusfar via tips on this forum or trial and error.

 

[aharlan001]

The accumulator pressure needs to be 10.2 ish. Mpa-g in neutral. Keep bleeding the system with the recycled fluid. Start the bleed at the height accumulator. Then one front till on the bumpstops then one rear till on the bumpstops. Check the reservior then start and up to neutral. Next time you get it back up to neutral take a pic of the data from techstream. Pressure data from techstream in low is basically useless as a uHu above said. Earlier you had decent front and rear pressure in neutral and the accumulator was 7ish if i recall. Keep bleeding

I can share what worked for me. (Stop/start is engine below)

1. Begin in N (if you can) and fill the reservoir as high as it will go.
2. Open LR bleeder.
3. Start rig and ensure fluid comes out for 5 seconds. Close bleeder, stop rig. Recycle captured fluid into resevoir.
4. Repeat 2&3 on other 3 globes, then on accumulator.

This is how I fully chased air out on my rig. I had to do the full cycle 4-5 times IIRC. Your favorite music or podcast may help.

Due to this experience, I keep my fluid level in the reservoir about an inch above the plastic seam line when in N. If I ever run the reservoir dry in the event of going to H or even H+, it will be an Act of God and not my fault for not having enough fluid in the reservoir.

Edit: I'm not an AHC expert like other contributors to this thread, but I have obtained solutions to every problem I've encountered thusfar via tips on this forum or trial and error.

I really appreciate your input. Ok, I did 3 additional quarts of bleeding yesterday. I'll do another 5 when I can get a chance. Have not gotten to n since just after I cranked the torsion bars three turns. What do you make of the fact that I'm getting almost nothing out of the height accumulator when I bleed. Seems like this should mean something??? Fluid out the corners flows freely...

 

[ramangain]

If you are getting fluid from the globes, you should be registering some pressure in TS after a L to H cycle, even if it doesn't reach N. What is that pressure after the last bleed?

 

[aharlan001]

I mean bleeding out all 4 corners plus the accumulator. The Paddo method might call for that, but I'm not sure. Just make sure all the bleeders have been opened and plenty of fluid has had a chance to come out of each of those bleeders.

Ok, will do, any idea why I'm getting almost nothing

If you are getting fluid from the globes, you should be registering some pressure in TS after a L to H cycle, even if it doesn't reach N. What is that pressure after the last bleed?

After the last bleed and attempted l to n the front was 4.6, rear 0.0, height accumulator 6.5. After this

If you are getting fluid from the globes, you should be registering some pressure in TS after a L to H cycle, even if it doesn't reach N. What is that pressure after the last bleed?

Fluid comes from the globes no problem. I got ts data something like 4.5 front, 0.0 rear, 6.5 height accumulator after I tried to bleed the height accumulator last night... Usually I get a value for the rear too... I'll get some more ts numbers later when I can bleed more

 

[2001LC]

While I watching, a few thoughts & questions.


Yr, miles, LC or LX..
Stock weight or loaded with toys like bumpers, winch, draw sliders, etc..
Stock T-bars and coils spring and are they factory installed...
Any overrides or such connected to AHC..
Is reservoir heavily stained..
Did you notice any solid matter in reservoir. Something that may clog reservoir to pump flow.
What was condition of fluid as it first came out..
What was height in N before being flush (ground to frame or axle to fender)
How many graduation from H to L before..
Any change T-bars like turning adjuster bolt CCW or change sensor position after..
Are sensor and arms locked in place..
Has height sensors been change from factory position, ever..
Do sensors look dirty, rusty, cruddy or is your undercarriage rusty..
If globs weak and or a change made shifting weight more to hydraulics. They can fail as in system tires to raise to N, with to much weight at start of raise.

 

[aharlan001]

I can share what worked for me. (Stop/start is engine below)

1. Begin in N (if you can) and fill the reservoir as high as it will go.
2. Open LR bleeder.
3. Start rig and ensure fluid comes out for 5 seconds. Close bleeder, stop rig. Recycle captured fluid into resevoir.
4. Repeat 2&3 on other 3 globes, then on accumulator.

This is how I fully chased air out on my rig. I had to do the full cycle 4-5 times IIRC. Your favorite music or podcast may help.

Due to this experience, I keep my fluid level in the reservoir about an inch above the plastic seam line when in N. If I ever run the reservoir dry in the event of going to H or even H+, it will be an Act of God and not my fault for not having enough fluid in the reservoir.

Edit: I'm not an AHC expert like other contributors to this thread, but I have obtained solutions to every problem I've encountered thusfar via tips on this forum or trial and error.

I have been bleeding with the truck off, refilling with recycled fluid, and recharging the globes by turning it on and letting the pump run. I do this cycle with every liter does this make a difference?

 

[aharlan001]

While I watching, a few thoughts & questions.


Yr, miles, LC or LX..
Stock weight or loaded with toys like bumpers, winch, draw sliders, etc..
Stock T-bars and coils spring and are they factory installed...
Any overrides or such connected to AHC..
Is reservoir heavily stained..
Did you notice any solid matter in reservoir. Something that may clog reservoir to pump flow.
What was condition of fluid as it first came out..
What was height in N before being flush (ground to frame or axle to fender)
How many graduation from H to L before..
Any change T-bars like turning adjuster bolt CCW or change sensor position after..
Are sensor and arms locked in place..
Has height sensors been change from factory position, ever..
Do sensors look dirty, rusty, cruddy or is your undercarriage rusty..
If globs weak and or a change made shifting weight more to hydraulics. They can fail as in system tires to raise to N, with to much weight at start of raise.

2007 163k lx470
Stock weight
As far as I can tell factory original t bars and rear springs.
Don't know what overrides would be, I am almost 100% original owner made no mods.
No reservoir staining. Minimal gunk in reservoir.
Fluid fluid blead out was initially white with bubbles then yellow with tiny bubbles now light red no bubbles.
When I bought the rig fluid was low. First thing I did was top it up with the proper fluid and test grads, functioned through heights and took about 20 seconds between. Got 9 grads. Drove for 2 weeks no problem.
Height sensors look good. Minimal rust on the rig. The one time I got it to n the height sensors had reasonable values in ts

 

[LXKevin]

"Have not gotten to n since just after I cranked the torsion bars three turns. What do you make of the fact that I'm getting almost nothing out of the height accumulator when I bleed. Seems like this should mean something??? Fluid out the corners

Getting almost nothing from the accumulator. May be air, may be a clogged bleeder, may be electrical- Open Techstream go in the active test page and check that each of relay/solenoid responds to on/off command and the report back.

 

[aharlan001]

Always happy to try something new. So with each test on lit up for about 1 second. With main relay, motor relay, front leveling solenoid, rear leveling solenoid I could actually hear something happening when it was activated. With accumulator solenoid, front gate solenoid, and rear gate solenoid I heard nothing... not sure what this means...