New Globes but Accumulator pressure dropped (1 Viewer)

Joined
Nov 13, 2020
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Wilmington DE 19807
I’ve read a ton of amazing expertise on the forum here over the last year. Hoping someone can offer some direction for me.

I’m original owner of 2000 LX470 with 197,000 mi.
I purchased new globes from Japan and had my long time Lexus mechanic do the install. Went from 7 ticks to 12-13 ticks and truck feels more solid and stable. Still feels harsh on expansion joints and alligatored asphalt, but better than before. Front and rear pressures both improved but Accumulator pressure dropped from 10.7 to 8.6. See pics.

Before the work I could go from L - N and N - Hi quickly. Maybe 7- 8 secs each. Now it’s much slower. 16 secs L - N and 16 secs N - H.

My first guess is the post-install bleed to remove any air wasn’t done enough? Can I focus on partial bleeding from the Accumulator alone, or will I need to also bleed all 4 corners? Or do a full bleed and replace AHC fluid completely again ...in case the pump got some air? Is there a best position (L or N or H) to have it in when partial bleeding?

Or is there another gremlin that could be the issue?

Many thanks to any and all for your insights and advice!

C4BA496D-5CCA-4D63-8CF8-37972BA7A10B.jpeg


586F2254-5C7D-46D2-890E-F25B62678B27.jpeg
 

uHu

Bridgeburner
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Oslo, Norway
Generally, there is no connection between the state of the globes and the pressures. The height adjustment will work fine even if you remove the globes and blind them, and the pressures will be according to the state and adjustment of the steel springs. With worn (flat) globes, there will be less (space for) fluid to push through the valves, and the lifting from Lo to N to Hi will be faster than with new globes. With new, good globes, the pump will have to compress much more nitrogen when lifting the truck. Your lifting time is now normal.

The change in pressure you see between before and after could be random, or a result of time. That also goes for the accumulator pressure, but it does appear to be low. You should run several tests/readings before concluding anything.

You could still have some air/nitrogen trapped in the fluid, and the nitrogen dissolved in the fluid between the actuators and the shocks, and inside the shocks, will take som time to work it's way to the bleeders. It's always good to bleed several times.
 
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Joined
Nov 13, 2020
Messages
14
Location
Wilmington DE 19807
Generally, there is no connection between the state of the globes and the pressures. The height adjustment will work fine even if you remove the globes and blind them, and the pressures will be according to the state and adjustment of the steel springs. With worn (flat) globes, there will be less (space for) fluid to push through the valves, and the lifting from Lo to N to Hi will be faster than with new globes. With new, good globes, the pump will have to compress much more nitrogen when lifting the truck.

The change in pressure you see between before and after could be random, or a result of time. That also goes for the accumulator pressure, but it does appear to be low. You should run several tests/readings before concluding anything.

You could still have some air trapped in the fluid, and the nitrogen dissolved in the fluid between the actuators and the shocks, and inside the shocks, will take som time to work it's way to the bleeders. It's always good to bleed several times.

Awesome!

I suspected (naively) that the accumulator pressure played a role in lowering and raising L-N-H and since that pressure dropped I was getting much slower times.

Sounds like the pump at the reservoir is the sole workhorse to do that raising L-N-H? Is there a health check or diagnostic to run specifically for pump health?

No codes showed up recently when Lexus did a complete scan for me. My mechanic is very capable and seasoned but hasn’t done much LX AHC work in a long time. I’ll check back with him for diagnostics and ideas once I’m better informed here.

I’d read awhile ago that ANY air in the system would affect proper functioning, and I wasn’t there to observe his bleed process after installing new globes. I suspected air was interfering in some way, but only guessing. Would you do a full drain and refill process to cover air in pump or do some partial bleeds from all corners + accumulator?

With a healthy system, is there an average (or range) number of seconds that I should expect for each going L-N, pause 20 secs, then N-H? What I have now seems painfully slow.

Thanks for your time, ideas and expertise!
 
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I agree with @uHu and I'll ask and add:

What are the (quick measurements) axle center to fenders wells (bottom of) measurements. After driving and raising front L to H a few times to settle and somewhat bleed!

I ask because you front pressure needs lowering to near 6.8 - 6.9Mpa.
Your accumulator should come in at ~ 10.5Mpa.

You may need T-bar adjustments to cross level and bring pressure down, caring more on T-bars.
You'll also shoot for about 3/4" drop (rake) in front. This is done be adjusting sensors. Typically if never adjusted you do not need to touch them. But sometimes someone has adjusted to give a sensor lift or some other reason like accident.

Additionally, replacing old factory installed coils (rear springs) with new OEM coils. Benefits most every AHC system out there today in our aging fleet.
I use Land Cruiser AHC coils and 30mm spacers in LC & LX. Works well to improve ride and give long life to globes.

IMHO: The idea is to carry as little weight as possibly on AHC, staying within pressure low limit specs, with ~ 3/4" rake and side to side level. (More rake, can help reduce HWY wandering, less rake increases wandering)
 

uHu

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The specs for lifting from Lo to N, or from N to Hi, is max 15 sec, but that is assuming that the pressures and heights are in spec, and you have no air in the fluid. Spec is 10 sec or less to lower it between each of the height settings.

Bleeding more is good, but no need to drain from the top unless the fluid looks bad; it's at the bottom end the pollution happens. The fluid does not circulate in this system, only moves a bit back and forth.
 

ramangain

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Speaking from experience, you need to keep bleeding the system (recycle the fluid to keep costs down) to get the accumulator pressure back to the "normal" range (slightly above 10 MPa). It sucks, and I had to do it 5-6 times to chase air out of the system. However, this process works and gets you to the desired result.

There may be a more systematic method to achieve the result faster, but sometimes you end up spending more time refining a process than a brute-force method.
 
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likely in the salvage yard
Joined
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You guys are the best! Thank you.

I’m going to reconfirm hub to fender heights which were in balance and spec last I checked. The TBs were not adjusted after the new globes. I wanted to drive a bit, settle in and start adjusting after that.
I’ll adjust the TBs to get closer to spec pressures and then recheck all pressures on F and R and Accumulator. I hoping that brings up the Accumulator pressure, per the advice. Fresh rear coils are in my near future.

I’d like to do some partial bleeds and recycle the new fluid that just went in with the new globes.

Do you recommend partial bleed from all 5 screws?

Should I do the bleeds while in L or N or H?

I’m looking for any tiny bubbles to stop, then immediately tighten the screw back at each location.

Many thanks to everyone who jumped in with perspectives. Very helpful for me!
 

ramangain

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FWIW I don't recall seeing any bubbles at all at the globes, but I admit to just going through the motions on each bleed session and wasn't paying a bunch of attention, especially after the 2nd bleed. The biggest change was in how much I could empty from the accumulator. At first it was very little, then after each bleed and refill, I could get more out of the accumulator. Then BAM, I hit the previous accumulator pressure (before AHC fluid exchange), probably yelled a "fu(k yeah", and wrapped it all up.

Best of luck getting it done quickly and with minimal hassle. :beer:
 

uHu

Bridgeburner
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... Should I do the bleeds while in L or N or H? ...
That depends on how much fluid you want to bleed. If at Lo, hardly any fluid will come out, as there isn't much pressure in the circuit, and not much downward travel left, if any.
If at Hi, you will get the most out. Remember that the front is one circuit, and the rear is one, meaning that when you bleed one side, that end will drop down and there will be no pressure to bleed on the other side. I.e. you have to let the pump lift the truck up again for bleeding the other side of that circuit/end.
 
Joined
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Messages
316
Location
Brisbane, Australia
I’ve read a ton of amazing expertise on the forum here over the last year. Hoping someone can offer some direction for me.

I’m original owner of 2000 LX470 with 197,000 mi.
I purchased new globes from Japan and had my long time Lexus mechanic do the install. Went from 7 ticks to 12-13 ticks and truck feels more solid and stable. Still feels harsh on expansion joints and alligatored asphalt, but better than before. Front and rear pressures both improved but Accumulator pressure dropped from 10.7 to 8.6. See pics.

Before the work I could go from L - N and N - Hi quickly. Maybe 7- 8 secs each. Now it’s much slower. 16 secs L - N and 16 secs N - H.

My first guess is the post-install bleed to remove any air wasn’t done enough? Can I focus on partial bleeding from the Accumulator alone, or will I need to also bleed all 4 corners? Or do a full bleed and replace AHC fluid completely again ...in case the pump got some air? Is there a best position (L or N or H) to have it in when partial bleeding?

Or is there another gremlin that could be the issue?

Many thanks to any and all for your insights and advice!

View attachment 2612660

View attachment 2612661

You already have all the answers you need in the earlier replies and maybe it is stating the obvious but it is good to be very sure that the AHC Pump actually has finished recharging the Height Control Accumulator at the end of the LO to N raise – leave say a 30 second gap after the raise shows the green light at N and before accepting the Height Control Accumulator pressure reading. If all is working as it should, the Height Control Accumulator discharges its pressure at the beginning of the raise from “LO”. The recharge of Height Control Accumulator happens after the raise is completed and is the last thing completed in the overall sequence of events and the last pressure to be measured by the single Pressure Sensor at the AHC Pump. So the Height Control Accumulator pressure needs to be read when the recharge is completed. If you have Techstream connected and running at the start of the raise you can watch all three pressures (Front, Rear and Accumulator) build up. You also can watch the instructions the AHC ECU is giving to the solenoid valve at the front of the Height Control Accumulator (“SLAC” - Solenoid Accumulator - on Techstream) -- although you should be able hear and/or feel it working. Ditto the ECU instructions to the Front and Rear solenoid levelling valves in the Control Valve Assembly, respectively “SLFL” – Solenoid Valve Front Level and “SLRL” – Solenoid Valve Rear Level. These open and close as the Front and Rear of the vehicle shuffle upwards during the raise. It all adds to understanding of the system.
 
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LndXrsr

AHC Aficionado
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You already have all the answers you need in the earlier replies and maybe it is stating the obvious but it is good to be very sure that the AHC Pump actually has finished recharging the Height Control Accumulator at the end of the LO to N raise – leave say a 30 second gap after the raise shows the green light at N and before accepting the Height Control Accumulator pressure reading.

^^^This. Techstream's sampling rate is about once every second and can sometimes result in goofy readings. Best to repeat each reading 3-4 times before being certain of a value. Occaisionally, it will stop sampling the accumulator before it has completely repressurized at the end of a N-->L-->N cycle.

If you are getting truly low readings, just keep bleeding and recycling fluid and I suspect you'll get the results you're looking for.
 

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