L322 Air Suspension Conundrum

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Scotty99

Member
Posts
21
Location
Herefordshire
Hello,

I’ve got a real conundrum with my air suspension front n/s. A couple of weeks ago I had a suspension error come up on the dash. Front n/s air bag had sprung a leak so had it replaced by my local Indy LR specialist. About three days later after the vehicle had stood overnight I noticed it was down a little on, yes you’ve guessed it, front n/s. Took it back to my Indy LR specialist, they had it for three days but could not find an air leak anywhere in the whole system. They believe the system control unit is letting out air from the front n/s as it might be thinking it’s at the wrong height, they suspect it might be an electrical fault in the air suspension loom causing this to happen.

However it has occurred to me could it be fault with the height sensor front n/s that is causing the deflation.

What do people think? Any ideas?
 
If all the corners are normal like this and the car sitting correctly then I suspect the height sensors are ok

1707502754132.png
 
There could still be a dead spot on the sensor. If you have a test meter you could check the resistance to make sure it changes evenly as you move the sensor arm.
 
I would have to go for a leak personally as first port of call. It doesn't have to be the bag there are many other leak points in the system.

If all you corners look even on your screen the sensors are reading. What does it look like on screen when the front is down before you start the car?

You could pull the fuse/s for the system overnight to eliminate any electrical interference to the system.

They believe the system control unit is letting out air from the front n/s as it might be thinking it’s at the wrong height, they suspect it might be an electrical fault in the air suspension loom causing this to happen.

Although as much as this could be true, I would tend to believe they are at the end of their knowledge/want to work on the system.

If the car thought it was at the wrong height it would/should sit with that corner low all the time even when running, as the car believes it is at "target" height.

I wouldn't rule out the sensor totally yet, as they have obviously been in around that corner when doing the work. Where that corner was dangling. Which has been known to cause issues. But the car is design to beable to dangle a wheel.

That's my logic so far it works for me until I get shot down ;)

You dont mention year of car?


J
 
I would have to go for a leak personally as first port of call. It doesn't have to be the bag there are many other leak points in the system.

If all you corners look even on your screen the sensors are reading. What does it look like on screen when the front is down before you start the car?

You could pull the fuse/s for the system overnight to eliminate any electrical interference to the system.



Although as much as this could be true, I would tend to believe they are at the end of their knowledge/want to work on the system.

If the car thought it was at the wrong height it would/should sit with that corner low all the time even when running, as the car believes it is at "target" height.

I wouldn't rule out the sensor totally yet, as they have obviously been in around that corner when doing the work. Where that corner was dangling. Which has been known to cause issues. But the car is design to beable to dangle a wheel.

That's my logic so far it works for me until I get shot down ;)

You dont mention year of car?


J

It’s a 2007. Yes I’m beginning to suspect it’s the sensor that at fault. They say they have checked the whole system for a leak (air bags, connectors, valve blocks, compressor, reservoir etc) and can’t find one hence the theory that the system is deliberately but erroneously letting air out. So again back to sensor fault or electrical fault in the system affecting that corner.

I’m tempted to replace the sensor and recalibrate the system.
 
I would isolate it electrically overnight and see what happens first. Its a free test.

Does it do it every night? when ours first started to leak it didn't seem to do it every night depended where on our drive we parked.

And what does the screen look like when its down on that corner?

J
 
I would have to go for a leak personally as first port of call. It doesn't have to be the bag there are many other leak points in the system.

If all you corners look even on your screen the sensors are reading. What does it look like on screen when the front is down before you start the car?

You could pull the fuse/s for the system overnight to eliminate any electrical interference to the system.



Although as much as this could be true, I would tend to believe they are at the end of their knowledge/want to work on the system.

If the car thought it was at the wrong height it would/should sit with that corner low all the time even when running, as the car believes it is at "target" height.

I wouldn't rule out the sensor totally yet, as they have obviously been in around that corner when doing the work. Where that corner was dangling. Which has been known to cause issues. But the car is design to beable to dangle a wheel.

That's my logic so far it works for me until I get shot down ;)

You dont mention year of car?


J
+1 ^^^^^^^
 
I would isolate it electrically overnight and see what happens first. Its a free test.

Does it do it every night? when ours first started to leak it didn't seem to do it every night depended where on our drive we parked.

And what does the screen look like when its down on that corner?

J

The garage disconnected the battery over night and it still went down.
 
IMG_1924.jpeg
IMG_1923.jpeg
Some more analysis.

Two photos of the front wheels showing how the n/s has dropped overnight.

This is the display with the front n/s down before starting the engine.

IMG_1925.jpeg



This one is after the ignition is switched on and the suspension has levelled.

IMG_1926.jpeg


It looks like in the first one that the air suspension control unit thinks the front n/s is high which is maybe why it’s let air out.
 
Last edited:
It looks like in the first one that the air suspension control unit thinks the front n/s is high which is maybe why it’s let air out.

Look at the grey area under all the 4 wheels, Its telling you that the wheel is higher up in the suspension range than the others.
I.E the tyre is closer to the arch, is the way I see it.

But to be honest I have never looked at mine to confirm my thinking maybe somebody else can say.


The garage disconnected the battery over night and it still went down.

Tells me its not electrical then and is purely down to a leak.
Where is the next issue :oops: .

J
 
Look at the grey area under all the 4 wheels, Its telling you that the wheel is higher up in the suspension range than the others.
I.E the tyre is closer to the arch, is the way I see it.

But to be honest I have never looked at mine to confirm my thinking maybe somebody else can say.




Tells me its not electrical then and is purely down to a leak.
Where is the next issue :oops: .

J
Agree, a leak is the most likely cause.
 
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