Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
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
Leak from corner
valve to gallery
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
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!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 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!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 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 $$....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.