Air Suspension head scratcher

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Tapps33

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Keep me posted, if it does fall lets keep an eye on the fall as a function of time, so measure it something like every 4 to 8 hours.
It's my wife's DD, so I'll pull fuses and check heights beginning tomorrow evening.
 

Tapps33

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I find the observation that all 4 corners come down simultaneously to be really interesting. That tells me it needs to be in the "common" bit of the system because what are the odds of a simultaneous failure at all 4 corners - even if it IS a Rover...

If I have understood your problem properly, I find this in the mechanics manual trouble shooting section:

"Vehicle leans/tilts after
being left over-night or
for some days

Leaking air
spring(s)
Leak from corner
valve to gallery
Exhaust valve
stuck open"

The only option that addresses all 4 corners simultaneously would be "exhaust valve stuck open".
That means that each individual corner valve must need a fully pressurized system or they backflow, and when they backflow the corner would come down. And they would each backflow at slightly different rates.

You said you have the mechanics manual, but for those that do not, here is the pneumatics diagram (2014-2016)


View attachment 22866

Wow, so that would hint that if the gallery pressure drops, the four corners are not as isolated as assumed.... Which would lend itself to the thought that if the reservoir valve, or a rear gallery line I haven't replaced is cracked/failed, that could cause everything....but still, with fuse 3 pulled, the air suspension module shouldn't be trying to level the vehicle. Unless I'm dealing with deeper electronic issues such as power bleeding over from somewhere....but I'm not ready to start down that path yet. Or it means the system isn't 100% airtight and there is some bleed through even just sitting there. Although that makes no sense and is counter to everything I know about the system.

Just so everyone is clear, the front supply lines, reservoir block and rear valve block were replaced in November of 2018. The rear air lines are all still 2010 originals. The front valve block was replaced in July 2022 and I just replaced the compressor and reservoir tank 2 weeks ago.

I'm going to pull every fuse I can tomorrow and take measurements quite often and see how it does. I'll also measure from fender to wheel hub center (or maybe top/bottom of the LR badge as it's a little more accurate).
 

Tapps33

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The exhaust valve stuck open doesn't guarantee the vehicle will fall, once the springs are pressurized to reach the desired ride height each individual air spring is then isolated from the gallery (per a valve for each corner, 9/10/13/17 in your image). If each valve had a small leak but nothing else was leaking the vehicle would only fall a tiny amount but you would expect to see the gallery pressure go up... Another crazy idea (that's all I have at the moment! and I know the OP has replaced almost everything), there's a leak at the front and a different one at the rear, doesn't the computer monitor while the vehicle is off and open the cross link valve 2hrs after ignition off and then 6hrs thereafter?

This would cause the vehicle to slowly lower, so for example, the front left spring or pipe has a slow leak so that side goes down but the right side stays relatively still; after 2hrs the cross valve opens to equalize the pressure and so the right front falls a little (and in theory the left front would go up a little (as the pressure would go up a little)). At six hours after ignition off, the front left would have fallen some more but the front right would stay at the +2hr height; then the cross valve opens again and we once again see a height equalization and so on! Rinse and repeat at the rear!
I don't believe it opens the cross valve....although I could be wrong. If I read the manual correctly, it makes small downward adjustments to "level" the vehicle. This would indicate it exhausts the higher side valve to bring it down in line with the "leaking" side. Which again goes back to the fact that all 4 corners are independent and shouldn't move once inflated and there's no power to the Air Suspension module....hence why this is SO FRUSTRATING!

Screenshot 2023-01-19 at 12.35.18 PM.png


(For those who don't have the manual)
 

ftillier

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I've always pulled both fuses for the EAS when doing the sag tests. Can you spray all fittings with soapy water and see if you get any bubbles? That worked well for me in identifying leaks.
 

Longtrail

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I don't believe it opens the cross valve....although I could be wrong. If I read the manual correctly, it makes small downward adjustments to "level" the vehicle. This would indicate it exhausts the higher side valve to bring it down in line with the "leaking" side. Which again goes back to the fact that all 4 corners are independent and shouldn't move once inflated and there's no power to the Air Suspension module....hence why this is SO FRUSTRATING!

View attachment 22867

(For those who don't have the manual)
I think we're both assuming... It doesn't say which valve it opens and to be honest I don't know! By opening the valve on an individual corner you would also have to open the exhaust valve at the same time (to vent the pressure). In this scenario you're "throwing" away good air pressure. Opening the cross valve just equalizes the pressure across the axle and is much simpler! Like I say, I don't know and I'm also down in the weeds with my idea/suggestion!

"Wow, so that would hint that if the gallery pressure drops, the four corners are not as isolated as assumed...."
They have to be isolated, here's why!... If you raise the vehicle the first thing that happens is the middle valve is opened and the air from the reservoir raises the gallery pressure; at the same time the compressor comes on and the four corner valves are opened until the desired height is reached (meaning the pressure in the springs and gallery is equalized and is much higher than the normal operating PSI of the gallery). When the desired height is reached the four corner suspension valves are shut but the compressor continues to run meaning that the gallery and reservoir pressure continue to go up in readiness for a possible height change (it's a mechanical capacitor at the end of the day - it stores energy). Once the correct reservoir pressure is reached (on mine it was 258psi) the middle valve closes, the compressor shuts off and the exhaust valve dumps the gallery pressure down to 20 - 40psi range. Here's the reason there's isolation, 20 - 40psi in the airsprings would be insufficient to suspend the vehicle; if you were to equalize the four airsprings to the same pressure as the gallery you'd be on the bump stops. I figured this based on watching the valves open and close when requesting height changes. I think the gallery pressure is lowered to take stress out of the system; the volume of air in the gallery is relatively low in comparison to the reservoir and airsprings so dumping has little impact on the system...

Anyway - keep us posted as you continue to diagnose! I have a thread running here where I show some of the valves opening... Misery loves company!

 

txfromwi

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One way to diagnose, but would also introduce additional potential leak points.

Cut the lines at appropriate locations and install pressure rated manually operated shutoff valves.
One for each corner, then at additional strategic points in the "common bits" of the system.
Then it's easy to isolate each corner individually and in all possible permutations.
Process of elimination.

Brute force methodology...

Just sayin...
 

Tapps33

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Thanks for all the advice! For an apparently "simple" air system, this is really driving me crazy. I'm going to set the the suspension in extended height this afternoon and take measurements, then again in an hour, then just prior to the 2 hour mark, and so on and so on. (with the fuses pulled.).

I'll let you all know how it goes! I REALLY hope I don't have four corner issues....but, it'd give me an excuse to try and retrofit the dynamic suspension system from the RRS into the LR4!
 

Tapps33

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Ok, so here we gooo.....

I pulled engine bay fuses F3 and F26, 5amp and 20amp respectively at 4:40 yesterday. I measured 1 hour later, 3 hours later, then again this morning (15 hours later)

Time 0, 1hr, 3hrs, 15hrs
LF 19 3/8" - 19 3/8' - 19 3/8" - 18 7/8"
LR 20" - 20" - 19 7/8" - 19 3/8"
RF 19 1/2" - 19 1/2" - 19 1/2" - 18 3/4"
RR 19 1/4" - 19 1/4" - 19 1/8" - 17 7/8"

So, a couple thoughts.... I'm wondering how much of the 1/2" fall on the LF and LR is thermodynamic in nature? aka it was roughly 50 degrees out when I pulled the fuses, and about 38 degrees when I woke up. Would the temperature decrease cause the left side to fall that much? The RF appears to have fallen 3/4", which is greater than the left side, but it could be due to the greater strain of the RR dropping as much as it did.

There appears to be something wrong with the RR side, as it fell 1 3/8" overnight....even with possible thermodynamic reduction, that's distinctly greater than the other 3 struts. As I said above, the RF fell 3/4", which is 1/4" more than the left side....but if the RR was putting additional strain on the RF, that could account for the extra 1/4".

To answer a few questions, no, the fall rate doesn't appear to be linear in nature, at least not at first glance. There's a distinct possibility that the system stays up until the pressure decreases to a specific level, then it becomes linear....or more specifically , the leak is constant, but there's no fall until it reduces the internal pressure by several psi, then it actually starts to fall.

One other thing to note, as soon as I re-installed the fuses I heard the front valve block open up and begin to try and level the vehicle. So, in theory I can assume the leveling system was not functioning and the reductions are all from leaks and/or internal pressure reductions.

Anyone have any real world experience to add here? Unfortunately, I don't track the suspension enough to determine if it actually falls this much normally?

I should be able to pull the RR wheel on Tuesday and see if I can find any leaks in the system. I'll let everyone know what I find.

I'll say this....I've been focusing on the LF, it may be I've been looking in the wrong place....or I have/had more than one issue.
 

ftillier

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It's possible the other 3 corners are carrying more weight due to the RR losing pressure. I'd focus there, get that corner sorted, and then see how things look.
 

Tapps33

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It's possible the other 3 corners are carrying more weight due to the RR losing pressure. I'd focus there, get that corner sorted, and then see how things look.
I totally agree! the auto hobby shop on base isn't open today and its raining and nasty here...aka no driveway work, so tomorrow I'll go pull the wheel and see what I can find. Hopefully it's just a leaking Voss connection! If not....it'll be more $$....:afraid:
 

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