replacing AHC globes/accumulators (2 Viewers)
- Thread starter pete100
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Got my order put together and they have an extended holiday, no order processing until Monday May 10th.
Quick question on rear springs, for the couple of hundred bucks I was assuming it would be best practice to replace those at the time of globe swap out. Any opinions either way?
I found a thread on rear springs and there was a suggestion to go with the LC AHC springs over the LX ones as they may have a slightly higher rate. The thread had one person show minimal to no improvement with the LX springs. I just pass 200k so expecting there is some wear that has occurred.
LC AHC spring part numbers from the other thread:
RH 48231-6A770
LH 48231-6A780
Quick question on rear springs, for the couple of hundred bucks I was assuming it would be best practice to replace those at the time of globe swap out. Any opinions either way?
I found a thread on rear springs and there was a suggestion to go with the LC AHC springs over the LX ones as they may have a slightly higher rate. The thread had one person show minimal to no improvement with the LX springs. I just pass 200k so expecting there is some wear that has occurred.
LC AHC spring part numbers from the other thread:
RH 48231-6A770
LH 48231-6A780
That may have been me. I got zip with new springs, an outcome that I still don’t understand. Just got into spec recently with spacers.
30mm Ironman, purchased from a fellow Mudder.
I don’t recall anything noticeable when I put the new springs in. Gets iffy I think trying to assess small changes in this kind of stuff. When you’re focusing on it, you feel everything.
I did notice quite a change when I swapped out all the rubber in the front, though. (Haven’t gotten to everything in the back.)
And new globes made a big difference.
Yes, did bushings and sway bars at least a year before. Really softened the ride after I did - front only. I've swapped out a couple of bushings on the back - the easier ones to get to.
The globes made the biggest difference in handling, stability and road hold (as opposed to bumpy ride improvement), IMO.
Hmm, I probably need to do this too. My situation is I'm about 2.5 years into owning this. When I did the AHC fluid flush I had 8-9 graduations. Since then I've noticed having issues when loaded up where it stays in low or at least won't raise up after loading it. I also have all sorts of squeaks and noise when hitting bumps in the road.
Is there a thread covering the bushings? Wasn't on my radar to research to understand if I just need to search.
Try this one:
When & how to replace stabilizer bar, bushings, cushions & links (AKA sway bar)
Would you say I waited to long to change my bushings! But link breaking is not the only reason why I say to long. I found not only did Link rust through, but I also removed a ~1/16" of rust off top & bottom of stabilizer bar recess that the cushions sets in. I then found the stabilizer bar...
forum.ih8mud.com
I can feel the ride quality change and have observes techstream readings reflecting the change, but I didn’t test that for harshness or anything like that - I was on a smooth stretch of road when I did that.
I may give that a try, though - thanks.
That’s new as of yesterday, I think. I just bought a bunch of stuff from Amayama’s UAE supplier that I need before Mid June. We’ll see how that goes.
If it won't raise up, that's a pressure problem and globes and bushings are 100% unrelated, FYI.
Of course! My rear globes s*** the bed this afternoon. I sent Impex an email to clarify the warning the message. If they say it's going to be a week or more I guess I'll be paying twice as much on Ebay.
Global supply chains have been bananas lately. Tariffs. Fires in 2020. Pandemic. Civil Unrest. Postal workers stretched thin with record shipping levels. Cargo freighter blocking $4B+ in the Suez for weeks. More pandemic. I think there was another major supply chain issue in 2020 as well.
The last 12-15 months have been a new kind of bizarre. Hopefully the Japan issue is over swiftly.
Just in case it needs to be mentioned, in the HI/LO test a difference of 14 graduations at AHC tank = near new 'globes' with AHC system at correct neutral pressures; 7 graduations at AHC tank = investigate cause, usually means time to change 'globes'. However, per FSM, this test must be done at correct AHC pressures. Otherwise the test and conclusions are close to meaningless.
At correct AHC pressures, 8 to 9 graduations usually means that 'globes' overall are 'just OK' and ride quality is starting to deteriorate noticeably. If so, suggest through the rest of 2021 and early 2022, be on the lookout for replacement 'globes' at a good price, ready for replacement.
The point is that if AHC pressures are excessive, then the nitrogen pressure behind membranes in the 'globes' will struggle to push hard enough to force enough fluid back to the AHC tank in this test. Then the HI/LO test results will not be comparable with FSM recommendations because the test was conducted under different conditions.
Note that AHC pressure measurements by themselves tell nothing about 'globe' condition. AHC pressures can be correctly set and read on Techstream with zero nitrogen pressure in the 'globes' or even with 'globes' blanked off. The AHC raise "LO" > "N" > "HI" function still works with zero nitrogen pressure in the 'globes' or with 'globes' blanked off. The AHC pressure readings reflect the share of load carried by the hydraulic AHC system, and nothing else. The vehicle will raise provided that the AHC Pump (assisted by the Height Control Accumulator) can deliver sufficient pressure to lift the vehicle weight using the mis-named 'shock absorbers' as hydraulic rams, nothing to do with the 'globes'
However, in this condition there also will be zero damping and a very, very rough, 'springy' ride.
Causes of excessive AHC pressures:
- vehicle and AHC system are overloaded -- for load guidance see https://lc100e.github.io/manual/ -- Go to tabs at Index Panel, top left of opening page -- New Car Features (first item in the list) > CHASSIS > Suspension > Active Height Control Suspension & Skyhook TEMS -- then go to second page of this article,
- tired Front Torsion Bars and tired Rear Springs carry insufficient load share, AHC carries excessive load share and operates at higher than specified pressure, requires transfer of load from AHC system to Torsion Bars and Springs to reduce AHC pressures,
- vehicle is set too high (hub-to-fender should be Front 19.75 inches, Rear 20.50 inches). Excessive height means less weight carried by Torsion Bars and Springs, more weight carried by AHC system, causing higher AHC pressures,
- Start with checking that AHC pressures are not excessive,
- Check that tyre pressures are reasonable,
- Review all rubber bushes everywhere,
- Review wheel bearings
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OK, I'll say my pressures are in speck, but I only had 6-7 graduations before yesterday. Yesterday afternoon the rear end dropped to the bump stops while my wife was driving home.
While cycling from L-H a couple times, once I was able to get the rear to raise to about the N position while in H. The front seems to work fine, but the rear doesn't budge now. In tech stream the rear pressure doesn't change, it's just 9.0. The rear pressure was in spec as of about 1-2 months ago. I flushed the fluid about 6-months ago.
So I know the globes need to be replaced, but if they wouldn't cause the rear to drop, what would? I sticking solenoid? I ran the solenoid checks in tech stream, but I didn't notice anything unusual. Of course I don't know what I'm looking for anyway.
Advice?
While cycling from L-H a couple times, once I was able to get the rear to raise to about the N position while in H. The front seems to work fine, but the rear doesn't budge now. In tech stream the rear pressure doesn't change, it's just 9.0. The rear pressure was in spec as of about 1-2 months ago. I flushed the fluid about 6-months ago.
So I know the globes need to be replaced, but if they wouldn't cause the rear to drop, what would? I sticking solenoid? I ran the solenoid checks in tech stream, but I didn't notice anything unusual. Of course I don't know what I'm looking for anyway.
Advice?
Techstream Rear pressure is way higher than FSM spec at 9.0 Mpa -- range is 5.6 to 6.7 MPa with standard tank in FSM conditions, 5.7 to 7.0 Mpa – with additional sub-tank in FSM conditions. This overpressure possibly is enough to cause the Rear to drop and/or be reluctant to raise. Can you identify a cause of this high pressure? Vehicle load? Attached armour? What is your tape-measured Rear hub-to-fender distance? (Normal is 20.50 inches, higher than normal means higher Rear pressure).
The next ports of call for height-related symptoms are the condition of the three Height Control Sensors (two Front, one Rear) and their connectors and harnesses. These may or may not show as a DTC in Techstream.
Usually removal, cleaning, electrical checking of Height Control Sensors per FSM or IH8MUD posts is necessary and replacement may need to be considered.
The Techstream Height Sensor readings may give cause for suspicion. What are your Sensor readings on Techstream? These should be close to zero +/- 0.2 inches.
If there are wide differences in the Techstream Height Sensor readings, it may only be a matter of checking front cross-level then adjusting all hub-to-fender heights using the Height Control Sensor adjusters.
If wide differences in Sensor readings and/or AHC behaviour have occurred suddenly as described, then suspicion falls on the internal condition of the Sensors and their connectors and harness. These things have a finite life and slowly but surely become 'worn out'. Given wear of the internal carbon track, corrosion of internal parts, ingress of moisture/salt, the day will come when the voltage signal from a Sensor becomes erratic and inconsistent. This may seem sudden when really it is the final consequence of wear or deterioration over time.
If the ECU receives erratic and/or widely different signals from Height Control Sensors, then erratic AHC performance will occur. If signals and differences are outside the range accepted by the ECU, then the ECU will put the system into 'fail safe mode' -- no adaptive damping, heights become fixed -- until the fault is rectified.
