Testing air suspension for leaks?

[powershift]

Is it one side or the other or both sides? Don't rule out the rear valve, a leak in one of the three valves could result in one side lowering, you need to look at the pneumatic diagrams to understand how the three valves in the one valve block work.

There was drop in 3 of 4 corners when measuring from the ground to the bottom of the fender trim right up the center-line of the wheel. I ran a 24 hr leak test while in off-road height with the fuse pulled last week. With these measurements below, the left front was on two blocks and had 0" change down to the 1/16" and it was the highest of all 3 wheels.

Right Front had a 5/16" drop and during leveling w/no cargo change it raised 1/4"
LF 0" drop and during leveling it dropped 1/8"
RR 1/4" drop leveled up 5/16"
LR 3/16" drop leveled 0"

I'm reading in the service manual that there are two corner valves and then another cross link valve within the front/rear valve blocks. The corner valves control air to an individual damper and the cross link controls air to both dampers. So it sounds like in the case where one corner is down, it could be from the corner valve in the valve block. Is that what you meant? I'm curious if some leakage is expected or should all corners be perfect 0" drop?

 

[ryanjl]

The Arnott complaints are dated. I believe Arnott formerly sold rebuilt units that had quality problems. I've been running them in my LR4 for years without problem.

Edit to say that I've been running their new units for years, not the old rebuilt ones they used to sell.

 

[Longtrail]

I'm reading in the service manual that there are two corner valves and then another cross link valve within the front/rear valve blocks. The corner valves control air to an individual damper and the cross link controls air to both dampers. So it sounds like in the case where one corner is down, it could be from the corner valve in the valve block. Is that what you meant? I'm curious if some leakage is expected or should all corners be perfect 0" drop?

Yes, it's well known the desiccant in the compressor (to dry the air) starts to break down and distribute a fine powder in the hoses. That fine desiccant powder finally reaches the three respective valves (three at the front, three at the rear and two if I recall at the compressor) and has a slight impact on the valves ability to seal closed. It is for this reason that I recommend servicing the valves with new o'rings. I'd definitely do this as it's relatively cheap and straight forward before looking at replacing the air-springs. Relatively straight forward but... the rear is a pain in the "a" in terms of accessing the pipes but it's doable.

Also bear in mind, once the vehicle height has been reached (using approximately 250psi); the pressure is dropped in the gallery... what does this mean? It means that the spring side of the valve is a relatively high pressure while the other side of the valve (where the air compressor is situated - known as the gallery) is relatively low pressure (I suspect this is to save wear and tear on the hoses etc.). When vehicle height adjustment has been reached the gallery pressure is vented from 250 psi down to something closer to atmospheric ~14psi (the noise you hear when the system needs to vent). This difference in pressure between the spring side of the valve and the gallery side of the valve would allow the vehicle to lose height if there's a slight leak (air flows from high to low pressure).

 

[powershift]

Yes, it's well known the desiccant in the compressor (to dry the air) starts to break down and distribute a fine powder in the hoses. That fine desiccant powder finally reaches the three respective valves (three at the front, three at the rear and two if I recall at the compressor) and has a slight impact on the valves ability to seal closed. It is for this reason that I recommend servicing the valves with new o'rings. I'd definitely do this as it's relatively cheap and straight forward before looking at replacing the air-springs. Relatively straight forward but... the rear is a pain in the "a" in terms of accessing the pipes but it's doable.

Also bear in mind, once the vehicle height has been reached (using approximately 250psi); the pressure is dropped in the gallery... what does this mean? It means that the spring side of the valve is a relatively high pressure while the other side of the valve (where the air compressor is situated - known as the gallery) is relatively low pressure (I suspect this is to save wear and tear on the hoses etc.). When vehicle height adjustment has been reached the gallery pressure is vented from 250 psi down to something closer to atmospheric ~14psi (the noise you hear when the system needs to vent). This difference in pressure between the spring side of the valve and the gallery side of the valve would allow the vehicle to lose height if there's a slight leak (air flows from high to low pressure).

Thank you for sharing your knowledge. I'm going to get the courage to rebuilt the front/rear valve blocks as a preventative maintenance thing since I could do it on my own.

For the past few days I didn't park on blocks to level the cargo area and instead shimmed my air mattress. I did that as an experiment and found the rear isn't sagging so much to where I hit my head on the hatch the next day after parking lol. I totally clear the hatch when approaching the tailgate, but not when it was on blocks. It would be fine for the day but then it sagged. I look at the ground clearance too and it doesn't look like its leaking at all while not on blocks, but I'm going to rebuild the valve blocks and re-test leak measurements afterwards to see if there is change on and off blocks.

 

[Longtrail]

My pleasure, here's my detailed suspension thread, in particular I do the valves here (YouTube video links as well):

2012 LR4 Reluctant to lower from off-road suspension mode

Changing the dryer, if you have a Hitachi compressor, is straight forward. Hardest part will be disconnecting the hoses from the back side of the compressor (intake and exhaust hoses), and re-installing the compressor bracket when you reassemble due to a hard to reach bolt that need to be...

www.landroverworld.org

Other's have bought the o'ring kit from the same location and had success; getting the right size o'rings is a big deal so pay attention to where you source them. Feel free to ask questions! You also want to use small dabs of silicon grease on the o'rings when you reassemble the valves.

 

[gsxr]

The Arnott complaints are dated. I believe Arnott formerly sold rebuilt units that had quality problems. I've been running them in my LR4 for years without problem.

Arnott had a good reputation for quite a long time, along with lifetime warranty. That is no longer the case... now is a 2-year warranty from date of purchase, only for original purchaser. And, the complaints are starting to ramp up again, it seems something has changed with their components or process. Something to keep in mind if shopping for replacement air struts.

 

[ryanjl]

Arnott had a good reputation for quite a long time, along with lifetime warranty. That is no longer the case... now is a 2-year warranty from date of purchase, only for original purchaser. And, the complaints are starting to ramp up again, it seems something has changed with their components or process. Something to keep in mind if shopping for replacement air struts.

That stinks. Seems like the enshitification of things knows no bounds.

In that case, if I were in the market right now, I'd go with OE units from on of the UK-based suppliers.