AHC bleeding...found foam/bubbles. Bad sign?

[RL4x4]

I recently purchased a 2007 LX470 w/90k miles. The truck is totally stock and in very good condition with one owner since new and a full service history from one Lexus dealer. No accidents, etc.

The AHC fluid was changed for the first time at ~70k miles but there is no indication in any of the records that anything in the system has ever given any trouble or required replacement.

I find the ride to be a little bit firmer than I expected but I have nothing to compare it to other than even stiffer riding lifted 80 and 100 Series rigs.

Over the past week I have done the Hi to Lo fluid level test three times and each time I get the same result - the fluid level in the reservoir changes approx 8 or 9 graduations, which I understand is on the low side of the acceptable range.

Today I bled the AHC fluid just to make sure it was perfectly clear/clean and free of air bubbles or contamination. The front bled fine with the fluid coming out smoothly, although with a dark grey hue. The rear fluid was just as dark but at least 50% of it looked slightly foamy with tiny air bubbles that almost looked foamy when I poured it into a large drain pan.

Is the foamy rear fluid a sign that the accumulators are ruptured or leaking or is it normal?

Other than subjective ride-quality test or the drop-a-wheel-off-a-curb-test are there any official Toyota/Lexus tests to verify the condition of the accumulators?

I would be if I spent $1000 for new rear accumulators and the ride didn't improve!

Thoughts?

 

[DallasCrzr]

I can't speak to the technical details of the abc system however in my 99 the ride is pretty smooth when the knob is totally to comfort. If you're cruising down the highway you should definitely be able to tell an immediate difference when you go from total comfort to total sport.

I also believe that air bubbles can occur if the reservoir for the ahc was low and you put the truck in hi. Otherwise ill gladly sell you my accumulators when i tear out my ahc

 

[uHu]

The official t0yota test for the globes is the counting of notches on the reservoir, but there are preconditions. You heights and, most important, the Neutral Pressure has to be correct. As the coils and TBs go weaker over the years, the ahc pressure will rise, compressing the gas in the globes more and give a harder/harsher ride.

So, first check heights (Lo, N & Hi), then Neutral Pressure, and then count graduations.

The foam might be just from squeezing out thru the bleeder.

 

[ntsaint]

The foam might be just from squeezing out thru the bleeder.

Above is probably the case.

If the fluid is dark gray, consider flushing it. My 2006 AHC fluid was nearly black, and after flushing the ride quality changed (don't ask me how)...

 

[RL4x4]

So, first check heights (Lo, N & Hi), then Neutral Pressure, and then count graduations.

Fair enough. Next week I will have a FSM and the Techstream so I will be able to verify that everything is in-spec!

Update - I drove for 15 miles, raised and lowered the suspension a few times, and then re-bled the rear accumulators. This time the fluid came out a bit cleaner (obviously) and free of air bubbles or foam. My theory is that if the bubbles were caused by Nitrogen leaking from the accumulators into the fluid it must happen slowly over time which is why my fresh sample didn't have bubbles.

Anyone care to comment

 

[TeCKis300]

The foam might be just from squeezing out thru the bleeder.

I 3rd this. Often happens bleeding brakes as well. Air can sometimes come in around the bleeder screw threads as you back it out. How far did you unscrew the bleeder screw when you bled it?

Your car is a 2007. I wouldn't worry about premature failure at this age.

 

[MilkmanVX]

Fair enough. Next week I will have a FSM and the Techstream so I will be able to verify that everything is in-spec!

Update - I drove for 15 miles, raised and lowered the suspension a few times, and then re-bled the rear accumulators. This time the fluid came out a bit cleaner (obviously) and free of air bubbles or foam. My theory is that if the bubbles were caused by Nitrogen leaking from the accumulators into the fluid it must happen slowly over time which is why my fresh sample didn't have bubbles.

Anyone care to comment

When I bled my AHC, after some 150k plus miles (I don't think it had been bled before -ever), it hissed at first as gas came out -then fluid which if I remember correctly was dark and foamy ...
I never did figure out where the gas came from, only that after bleeding and refilling with the new fluid, my ride changed significantly.... (mind you, the smoothness is mostly only noticeable when I hit the rough stuff -on level tarmac, it seems the same as before) ....

Also, depending on how bad your fluid is/was, consider bleeding the entire system ... all four spheres AND the accumulator .... [where the spheres are what you are probably referring to as the accumulators and the accumulator, (where ehh, the fluid accumulates and then gets sent to the spheres ) is the big thingie that is under the passenger side door ]

 

[uHu]

....the accumulator, (where ehh, the fluid accumulates and then gets sent to the spheres ) is the big thingie that is under the passenger side door ]

RHD vehicle?
(Left side. Right?)

(Port side - Port Said - 'nuf said)

 

[MilkmanVX]

RHD vehicle?
(Left side. Right?)

(Port side - Port Said - 'nuf said)

ehhh ... yeah ... I keep forgetting you guys drive on the wrong side

Anyway, you can't miss it if you are bleeding either side -it is only on one

 

[RL4x4]

Update

Today I used the Techstream to check the Neutral Pressures.

See below for the BEFORE and AFTER screen shots.

The begining specs weren't too far off and cranking the TBs up four turns brought the front perfectly into spec.

I must be blind but I can't see the rear pressure spec in the FSM. A 'Mud member posted "Rear pressure - FSM calls for 5.6-6.7 MPa" which means I am on the very high end of the range. My plan is to add 5mm OME rear spring spacers to get the pressure down a bit.

 

[TeCKis300]

Nice!

Just to confirm, when you say 4 turns on the TB, you do mean 4 full 360 turns of the TB bolt?

How did you go about getting the techstream readout? Dealership?

 

[agaisin]

I must be blind but I can't see the rear pressure spec in the FSM. A 'Mud member posted "Rear pressure - FSM calls for 5.6-6.7 MPa" which means I am on the very high end of the range. My plan is to add 5mm OME rear spring spacers to get the pressure down a bit.

I'm looking at it now and here are the specs from the 05 LX470 FSM:
Front using Handheld Tester: 6.9 +/- 0.5 MPa (70 +/- 5 kgf/cm2 , 996 +/- 71 psi)
Rear using Handheld Tester: 5.6 - 6.7 MPa (57 - 68 kgf/cm2 , 811 - 967 psi)

(with Handheld Tester the pressure measurements are at taken at the pump rather than the actual pressure at the accumulator so the readings with Handheld Tester/Techstream are higher than these:
Front w/out Handheld Tester: 5.7 +/- 0.3 MPa (58 +/- 3 kgf/cm2 , 825 +/- 43 psi)
Rear w/out Handheld Tester: 4.4 - 5.5 MPa (45 - 56 kgf/cm2 , 640 - 797 psi)
)

The Rear pressure for Techstream is under the section titled "INSPECT PRESSURE VALUE OF REAR SHOCK ABSORBER (IN CASE OF USING LEXUS HAND-HELD TESTER)".

Your pressure in the rear of 6.5 is technically within spec (5.6 to 6.7) so as long as it's comfortable to you, I wouldn't even bother with it.

I will point out though that step number one before checking/adjusting neutral pressure is to make sure vehicle height is correct (refer to spec in FSM). So for example if for some reason your rear height is too high, that would cause your neutral pressure to be too high and the real fix might simply be to lower the rear a tad. If on the other hand your rear pressure is too low then after you've raised the rear to spec you would probably find your rear pressure to be way too high and out of spec.

As others have pointed out in the past, if your rear height is correct and your rear pressure is still too high, it's a sign that your springs are sagging and technically need to be replaced (iirc they're ~100ea.).

 

[RL4x4]

Just to confirm, when you say 4 turns on the TB, you do mean 4 full 360 turns of the TB bolt?

How did you go about getting the techstream readout? Dealership?

Correct, four full 360deg turns to lower the front pressure by approx 1bar.

A forum member helped me with the Techstream software and I bought a Tactrix 2.0 cable. Very useful combo! I also used the Techstream to calibrate my VGRS steering because the wheel was slightly off center.

Annoyingly I can't get the Techstream to turn off the automatic tilt/telescope steering wheel feature. It is listed in the options and I know the Lexus dealer can turn it off but my Techstream won't allow this function

 

[agaisin]

RL4x4 - how do you like the techstream/cable setup so far? Seems like you figured out the neutral pressure pretty quickly.

 

[RL4x4]

Your pressure in the rear of 6.5 is technically within spec (5.6 to 6.7) so as long as it's comfortable to you, I wouldn't even bother with it.

I will point out though that step number one before checking/adjusting neutral pressure is to make sure vehicle height is correct (refer to spec in FSM). So for example if for some reason your rear height is too high, that would cause your neutral pressure to be too high and the real fix might simply be to lower the rear a tad. If on the other hand your rear pressure is too low then after you've raised the rear to spec you would probably find your rear pressure to be way too high and out of spec.

As others have pointed out in the past, if your rear height is correct and your rear pressure is still too high, it's a sign that your springs are sagging and technically need to be replaced (iirc they're ~100ea.).

RL4x4 - how do you like the techstream/cable setup so far? Seems like you figured out the neutral pressure pretty quickly.

Point taken re checking to make sure the ride height is in-spec before checking the neutral pressures. Having said that, and FWIW, my truck looks right and I like the current heights so even if they are not technically correct (which they likely are) I don't want to raise or lower it New rear springs are cheap but since my pressure is so close to being correct I will just try $25 worth of OME spacers to see what happens.

I love the Techstream and it is fairly easy to use but I really want to figure out why I can't access the ECU that will allow me to turn off the auto key-off steering wheel tilt/telescope "feature" Thanks again for all the help you gave me!

 

[uHu]

Reading the techstream data, I see that your front sensors are out of spec, in particular the left one. And when the right one "goes the other way", you have a situation which can hamper the operation on un-even ground.
- The front height is adjusted to the average of the left and right sensor.
- If the left and right sensor differ more than a certain value, the ahc will not hoist or lower. IIUC, this threshold value depends on Lo or Hi range, and DL on or off.

 

[RL4x4]

Reading the techstream data, I see that your front sensors are out of spec, in particular the left one. And when the right one "goes the other way", you have a situation which can hamper the operation on un-even ground.
- The front height is adjusted to the average of the left and right sensor.
- If the left and right sensor differ more than a certain value, the ahc will not hoist or lower. IIUC, this threshold value depends on Lo or Hi range, and DL on or off.

Thanks for noticing. I was wondering about those numbers being so far off!

FR 2.2mm
FL -6.2mm

Does this mean I need to raise the the FL sensor ('borrowed' photo attached) by sliding it up the slot or shortening the threaded rod until the Techstream reads about the same value as the RF?

Or maybe I need to lower the FL sensor position to acheive the correct number

 

[white_lx]

Annoyingly I can't get the Techstream to turn off the automatic tilt/telescope steering wheel feature. It is listed in the options and I know the Lexus dealer can turn it off but my Techstream won't allow this function

Same here. I have a '00 LX with Techstream and Tactrix. The dealer was able to switch it off years ago - so it does work!

I can not access any of the 'customize' menus with the Techstream/Tactrix combo. However, all other readouts of sensors (including AHC and engine) are available. Same behaviour on my '02 LS430.

 

[agaisin]

RL4x4 - have you been able to get to *any* of the customize menus? Is it just the one that contains automatic tilt/telescope you can't access?

I have been able to get to at least some of the customize features using TS and Tactrix on my 05. I will have to check if I can change the auto tilt/telescope or if it doesn't show up for me either.

 

[TeCKis300]

Do any of you have a hint as to how I can get the techstream software? I'd want to see if an OBD-II cable I have is capable of supporting it before I just in and buy a tactrix cable.