Air Suspension head scratcher

[Tapps33]

Hello all! So, here's my dilemma; I can't keep my LR4 from falling down. I have been trying to trace the leak for years....literally.

Some background: Back in early 2019, I replaced all three valve blocks, installed a new compressor (switched from Hitachi to AMK), and replaced all 4 air struts with new Arnott air struts. (The Hitachi had burnt out, and that's what starts the crazy system refresh). I then had everything reprogrammed and calibrated at my local stealership....mainly because I was on the road and didn't have access to my calibration tools. Everything was fine for a very a short time...maybe 4 months or so, and then I started to notice it was falling on it's face again, or at least the front appeared to be falling again. I assumed I had simply purchased a bum from valve block and replaced it. This helped, but didn't solve the problem. I then assumed I had a leak in one of my air lines and replaced the front supply lines from the valve block to the air struts, as well as from the compressor to the valve block.....still kept falling. So, when I had time I'd raise the suspension, pull the 5amp leveling fuse (#3 in the fuse block), and measure heights....and snoopy every connection I know of....I could never find a leak, and it would typically fall in the front. (FYI, I did try and find the leak BEFORE I replaced the lines, but I assumed it was hidden somewhere I couldn't get to) I have always assumed the problem was related to the driver's front air strut...until recently. Flash forward to about a year ago, and the front starts really falling again. I replaced the front valve block....again....and it definitely helps solve the issue of the front falling on it's face, but doesn't solve the overall problem. Thankfully (insert sarcastic face here) the compressor burnt itself out about a month ago and I put a new Arnott AMK compressor in the system as well as a new reservoir tank. (Mine was really rusty, and is now 13 years old so I figured, what the heck, might as well since I've got it in the air).

After all that, she still falls down overnight. I have raised it up, pulled fuse #3 and it still falls over night. I have traced every line, snoopy'd every strut connection, every valve block connection and pretty much every air line I could physically get to and still....no leak detected. I also thought perhaps I had bad suspension calibration that was driving the system to constantly try and level itself, so I re-calibrated it with my iiD tool. However, that wouldn't explain why it still falls with the leveling fuse pulled.

I am pretty much at my end at this point, but I do have 2 final theories I wanted to run by everyone. First, I wonder if I got a bad reservoir valve block back in 2019 when I swapped everything out? If this this is leaking somehow, it's got a direct internal connection to both the front and rear valve blocks....but in theory, it it's leaking, the front and rear solenoids should be closed, not allowing the movement or air to/from the struts.....unless it's one of those weird internal circular leaks....kinda like the front valve block issue? Second, I could have 4 bad air struts....but that seems HIGHLY unlikely....and REALLY expensive to test.

FYI, here's what my measurements look like when I pull the fuse: (As measured from the ground to the top of the wheel arch), I also made sure the temperature was very similar between when I took the initial measurements to when I took the follow on measurements as I thought air temp and the fact that I was measuring from the ground could affect my results.

Start ht 36hours later
LF. 34 7/8". 33 3/4". (1 1/8" drop)
LR. 35 1/8" 33 7/8". (1 1/4" drop)
RF 34 5/8". 32 3/4". (1 7/8" drop)
RR 35 1/8". 32 1/2" (2 5/8" drop)

Clearly it's falling on all 4 corners....appears to be greater on the right side...which is counter to what it appeared to have been focused on, which was the left front corner.

Finally, there are no error codes associated with this. (As opposed to when the compressor burnt out) I am also able to calibrate, raise/lower the suspension just fine.

Let the fun begin....what have I missed?

 

[ryanjl]

You pull the fuse and the whole vehicle falls? That tells me it's something in the middle, but I'm not sure what given all that you've replaced.

Something you can try that I saw on the LRTime youtube channel when they were searching for a leak: they could only see a leak in the front valveblock using soapy water when the valve block was actuating (i.e. when they were raising or lowering the suspension). Grab a second person to raise and lower the suspension as you spray the valve blocks. Yours may be the center valve block given all 4 corners are dropping.

 

[Tapps33]

You pull the fuse and the whole vehicle falls? That tells me it's something in the middle, but I'm not sure what given all that you've replaced.

Something you can try that I saw on the LRTime youtube channel when they were searching for a leak: they could only see a leak in the front valveblock using soapy water when the valve block was actuating (i.e. when they were raising or lowering the suspension). Grab a second person to raise and lower the suspension as you spray the valve blocks. Yours may be the center valve block given all 4 corners are dropping.

Hmmm....I never thought about trying to detect the leak during actuation. I'll give that a try in the next day or so. It's raining all day here and I don't have a garage.

And yes, the fact that all four corners drop is now officially driving me insane!

I'm really hoping I'm just doing something stupid like pulling the wrong fuse or something.

 

[Longtrail]

I really feel your pain, I'm going through a different but also annoying suspension issue... Thinking out loud...

I suspect you're going to need to think outside the box! If you open the middle solenoid valve all that does is connect the gallery (the air in all the pipes) to the reservoir, that would mean that the pressure to the front and rear valves and the exhaust valve would all become whatever the pressure in the reservoir happens to be (less any small pressure reduction). Are you confident that the pipes are all connected correctly on the middle valve?

This past weekend I removed the middle valve and so long as the front and rear valves don't open the pressure remains constant in the sprung side of the suspension and the vehicle will stay up...

For the suspension to really lower (and assuming for a minute that the complete system is airtight and all the valves are behaving) you have to open each of the front and rear valve blocks and the exhaust valve on the compressor... This would imply some wonky electronics! Ignoring the fuse disconnection is there anyway that the RLM ECU could be opening valves to reach some desired state, do you have anyway to monitor this?

Do you happen to know if the fall of the vehicle is gradual, for example the RR fell 2 5/8" over 36 hours, does it fall 1 5/16" (half) over 18hours, so is it a linear fall (which does suggest a leak somewhere)??? (or close to linear).

New valves, are they OEM? Have you pulled them apart and looked at the state of the o'rings, mine were very slightly white from desiccant, fitting new o'rings and adding a slight amount of silicon really helped my overnight sag.

I'll keep pondering as this is an interesting scenario!

 

[Longtrail]

Just one other thing, other sites mention removing the 20A fuse 26 to disable air suspension. I don't know the difference at the moment but it might be worth a look.

 

[Tapps33]

Just one other thing, other sites mention removing the 20A fuse 26 to disable air suspension. I don't know the difference at the moment but it might be worth a look.

Sometimes I have pulled both fuses, just in case. Although, to be fair, I didn't do it this last time. I'll pull them both this weekend when I can let the car sit for a day or two and see what happens.

 

[Tapps33]

I really feel your pain, I'm going through a different but also annoying suspension issue... Thinking out loud...

I suspect you're going to need to think outside the box! If you open the middle solenoid valve all that does is connect the gallery (the air in all the pipes) to the reservoir, that would mean that the pressure to the front and rear valves and the exhaust valve would all become whatever the pressure in the reservoir happens to be (less any small pressure reduction). Are you confident that the pipes are all connected correctly on the middle valve?

This past weekend I removed the middle valve and so long as the front and rear valves don't open the pressure remains constant in the sprung side of the suspension and the vehicle will stay up...

For the suspension to really lower (and assuming for a minute that the complete system is airtight and all the valves are behaving) you have to open each of the front and rear valve blocks and the exhaust valve on the compressor... This would imply some wonky electronics! Ignoring the fuse disconnection is there anyway that the RLM ECU could be opening valves to reach some desired state, do you have anyway to monitor this?

Do you happen to know if the fall of the vehicle is gradual, for example the RR fell 2 5/8" over 36 hours, does it fall 1 5/16" (half) over 18hours, so is it a linear fall (which does suggest a leak somewhere)??? (or close to linear).

New valves, are they OEM? Have you pulled them apart and looked at the state of the o'rings, mine were very slightly white from desiccant, fitting new o'rings and adding a slight amount of silicon really helped my overnight sag.

I'll keep pondering as this is an interesting scenario!

Thanks for the thoughts, as I agree with you 100%....it doesn't make any sense. for all 4 corners to fall, my thought is that the auto-leveling system has to be working. Because, you're right, even if the reservoir junction block is leaking, it'll just bleed off the gallery pressure....in theory the front and rear valve block solenoids should be 100% closed.

Oh yeah, almost forgot to add, I used OEM valve blocks all the way around....and yes, my wallet is still screaming! In fairness, I used a cheap aftermarket front valve block, but then the nose fell, so I went OEM with its replacement.

I do know that all 4 corner valves are working just fine as I was able to calibrate the system with no issues...each strut was adjustable up and down...cause you know I always overshot the measurement and had to go back....multiple times.

I re-read the shop manual and all the solenoids default closed, and then when they're energized open up. Double checking the wiring diagram, the air suspension module controls both the power and ground for the valves individually....so, if I had a short, in theory it'd only be on one strut, and I should get a code as the voltage would be out of limits....in theory.

I just can't help but think something's off in the air suspension module....and maybe I'm just missing the correct fuse....I have made dumber mistakes before! LOL!

Everything seems the point to the air suspension module constantly trying to level, but never actually getting there. However, all my ride height sensors appear to be reading normally....but perhaps one is a little wacky and hasn't 100% "failed" so it's throwing everything off?

Kinda thinking out loud here....

 

[Longtrail]

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.

 

[txfromwi]

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)

 

[Longtrail]

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!