One corner drops overnight - to bumpstops

[Leo]

RRS been behaving itself, but since last weekend it's been dropping down to the bumpstop on the drivers side rear corner. Lifts itself once started.

What could be the issue?

Thanks in advance!

[jonesfam]

I suspect your car may be drunk.:)

[sniegy]

If its only one corner, sounds like the air spring itself.
Try spraying some soapy water around the air spring & run it through its height settings, you may be able to see where!

HTH. Cheers.;)

[Leo]

If its only one corner, sounds like the air spring itself.


:eek2: If it is a punctured spring, can they be repaired? Bet they ain't cheap...

[Disco4SE]

Sounds like you have a lazy arse in the garage :)

[Neil P]

but since last weekend it's been dropping down to the bumpstop on the drivers side rear corner.

Disconnect the battery ( over-night ) and see if it still drops.
If it doesn't , it isn't a leak.

[gghaggis]

More likely a leak at the valve block or tubing to the bag than the bag itself. Pump it up, remove the rear passenger wheel and check for leaks (with soapy water) around the valve block located on the rear strut tower.

Cheers,

Gordon

[bbyer]

Disconnect the battery ( over-night ) and see if it still drops.
If it doesn't , it isn't a leak.

Removing the power eliminates all the questions of computers and wakeup etc, so that if one corner is down, the problem is what I call mechanical - and that is much less difficult to figure out than electrical.

Assuming mechanical, then the air is probably leaking from:

a) the air spring, which is possible, but not common, and to my knowledge, there is no repair, only replacement.

b) the air line between the block valve and the air spring. This seems to be the most common as due to rubbing/vibration, a pin hole/crack has developed.

c) the connection of the air line into either the air spring or the block valve. A soap solution can be squirted on to the top of the rear air spring fairly easily. It is not so easy however to get at the rear block valve but with the vehicle lifted, it may be sort of at least seen.

d) the block valve leaks internally - not all that common, but possible and fortunately, the block valve is fairly easy to replace, (once you get to it). Also if there is an internal leak, with the battery disconnected, I am not certain just where the air would exit that releases say from the air spring back to the compressor located exhaust valve - an interesting question that is. It just may be that if your Sport does not drop, the problem is with the block valve.

[Leo]

Seems like the car fixed itself, or sobered up. Been ok since I made the post on Tues. Sometimes I think LR program this kind of stuff into the ecus to give the cars 'character'.

No idea what could have caused the initial issue, though haven't yet checked for leaks - going to leave well alone as long as it's working ok.

[paddy119]

Hi Leo,
I had the exact same problem with my D4, it ended up being a faulty height sensor in the front passengers side air suspension. when you would turn the car off, the front left would not have a height reference and it would push up which in turn lowered the rear right. That's how the service manager at Newcastle explained it.
It looks pretty bad when you come out to the pride and joy and it looks drunk like that, to make it look bearable i would park it in access mode, and it did'nt seem to look as bad
Repaired under warranty
Cheers Pat

[bbyer]

Hi Leo,
I had the exact same problem with my D4, it ended up being a faulty height sensor in the front passengers side air suspension. when you would turn the car off, the front left would not have a height reference and it would push up which in turn lowered the rear right. That's how the service manager at Newcastle explained it. Repaired under warranty Cheers Pat

That fault is an interesting one. It relates to the wake up function built into the air systems logic where after engine shut down, on some random schedule, the system wakes up, decides if the vehicle is level or not and then reacts appropriately, or in your case, inappropriately.

What I do not understand is how does it know it is level, or not level?

My understanding is that there is some communication between the wheel sensor signals and the yaw sensor for the anti skid function. I accept that it cannot be just the wheel sensors as that would mean the vehicle would have to be parked on flat ground all the time with never a wheel(s) down in a rut or the like, or a wheel(s) higher on a lump.

I have looked at the wiring diagrams related to the yaw sensor and cannot see any direct wiring connection between the yaw sensor and the air system computer but I suppose that does not mean much given that data seems to "secretly" flow over the various computer busses at all hours of the day and night.

That is why when trouble shooting the air suspension, one has to disconnect the power to determine if the problems are solely mechanical or somehow also electrical related. In the case of the above example, an electrical problem with a wheel sensor sends wrong signals after engine shut down to the computers and hence bad instructions are then sent to various air valves. That tends to suggest it is just wheel sensors that provide level information, however I do not think the sensors are the sole source of data.

Hence the question, how does the car know is it not sitting level?

[Leo]

:eek: too clever for its own good!

[Graeme]

Hence the question, how does the car know is it not sitting level?
The 4 height sensor values for when the vehicle is level with respect to the ground (not the horizon) are stored in the suspension ecu. These are stored at height sensor calibration time. The ecu therefore knows how far each corner is from the correct height. The suspension ecu will level downwards at specific intervals after the ignition is turned-off even though the canbus is not operating, ie the suspension ecu does the periodic relevelling without regard to any other ecu or sensor not connected directly to it.

Edit: I would have expected an air leak at 1 corner (bag or air-line) to cause the others to also be lowered due to the periodic relevelling unless the suspension ecu main fuse was removed or the battery was disconnected to prevent that from happening. A height sensor giving plausible but incorrect signals would cause diagonal inconsistancies as the ecu relevels using faulty data. But I have experienced neither an air leak nor a faulty sensor.

[Neil P]

Been ok since I made the post on Tues. .

Five weeks on , and this is still OK ?

[Leo]

Yup, been ok since then. ( written while touching wood!!)