Disco II Air suspension – the definitive guide

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@Ice cold 1664

You may be better off placing this as a question in the Discovery section, rather than here, You have placed it as a comment on a sticky for the SLS, which a lot of people never look at unless they have an issue.

Have you checked the relay? If you do not have it then also download a cop of the Rave manual. It will help you trouble shoot.

Cheers

Thanks chaps, do you think the car will show a fault code? I just ask as there are not currently any warning lights.

I may have to invest in a Nanocom although I have just downloaded the Rave manual. Quick question, where would I find the compressor relay? Had a quick google to see where I can get one from and all it seems to bring up is forum sites talking about problems!
 
Hi all, have to say this is a massively informative and helpful thread and has helped me over the last few months of troubles however I am a little confused as to my current situation and I'm starting to feel like I might be throwing money at an endless problem with a 52 plate ES.

New air bags went on a couple of years ago and ride has been fine until December when one day the ride height just dropped at the rear just after driving away. left for a few days then was taking it to be looked at and the rear came up within a minute of driving away. Carried on as normal then a month later it dropped at the garage after a a short run start and stopped the engine a few times and it came up again. a week later it dropped again and never came back up so replaced the compressor and all seemed well until it dropped again after doing about 20 miles.

So then it starts to show a rear left sensor fault which was promptly replaced, and now it has risen about 2" higher on the side of the new sensor. I am thinking it may be a calibration issue but my garage tells me that they have never heard of such a thing. I'm wondering if sensors need to be replaced in pairs or like for like I think one side is original and the other is Britpart?

Thanks in advance for any help and suggestions
 
There is a calibration, but you don't need to go to a Main Stealer to get it done. Any good independent Landy specialist will be able to sort out your ride height issue. There's a small amount of extra info on Page 1 of this thread.
 
Hi all, have to say this is a massively informative and helpful thread and has helped me over the last few months of troubles however I am a little confused as to my current situation and I'm starting to feel like I might be throwing money at an endless problem with a 52 plate ES.

New air bags went on a couple of years ago and ride has been fine until December when one day the ride height just dropped at the rear just after driving away. left for a few days then was taking it to be looked at and the rear came up within a minute of driving away. Carried on as normal then a month later it dropped at the garage after a a short run start and stopped the engine a few times and it came up again. a week later it dropped again and never came back up so replaced the compressor and all seemed well until it dropped again after doing about 20 miles.

So then it starts to show a rear left sensor fault which was promptly replaced, and now it has risen about 2" higher on the side of the new sensor. I am thinking it may be a calibration issue but my garage tells me that they have never heard of such a thing. I'm wondering if sensors need to be replaced in pairs or like for like I think one side is original and the other is Britpart?

Thanks in advance for any help and suggestions

post your question on the Disco page and ask if anyone ins local who can help with diagnostics.

Cheers
 
Hello all, my name is Richard and I have a 2001 disco 2 td5 . unfortunately I have air ride issues. I first noticed a few days ago when I started getting flashed by oncoming traffic at night. did some work today , but not to sort for good. it had dropped a little, but will not raise again. I moved the height sensors at the back today and it dropped more, but would not go up again. after looking behind the rear light I didn't find and water, ended up doing a bypass on the wires and running the compressor by another battery, and it went up to the top.went for a little ride to reset it to normal ride height. so now I can drive it again, but there doesn't seem to be any current to the pump via the original wiring. ……… has anyone got any ideas please ? all fuses are good, but I have just got another relay so I can try it tomorrow. maybe the rear sensors ? not working properly ?

Stressed is not the word...
 
Disco II Air suspension – the definitive guide!
It's about time someone put all this into one place... so here it is!

All you will ever need to know about Air Suspension.


Simply put, the air suspension on the disco II consists of a couple of balloons at each back wheel.
A way of inflating them independently and a computer to monitor the height of the car and keep it all level.


The Disco II air suspension consists of the following components:

  • Air bags (balloons)
  • Pipes that join the air bags to the valve block and supply air to the compressor
  • A valve block to control independent inflation/deflation of the air bags
  • A compressor to supply compressed air
  • Air scrubbers/filters to clean and de-moisturise the air
  • Ride height sensors to feedback levelling and height information to the computer
  • A computer to control the valve operation and activation of the compressor

Component Locations:

  • Air bags:There are two air bags, one at each back wheel (there is no air suspension on the front)
  • Air Pipes: the supply air to the compressor runs along the chassis to the compressor from behind the top light cluster at the rear left hand side of the car. The supply to the air bags runs from the compressor valve block along the chassis to each of the rear air bags. There is a supply to the valve block that runs from the compressor.
  • The valve block: this is contained in the compressor unit black box on the outside of the chassis rail under the passenger seat (UK models)
  • Compressor: this is contained in the black box on the outside of the chassis rail under the passenger seat (UK models)
  • Air Scrubbers/Filters: there is an air scrubber on the compressor unit and the filter is behind the light cluster on the end of the supply pipe.
  • Ride height sensors: these are small matchbox size boxes with a plastic arm. They are attached to the chassis rail on each side at the front of the rear wheel arches and have a link bar which attaches to the rear arm to the axle and an electrical connection.
  • Computer: this is the SLABS ecu (‘Self Levelling’ and ABS ecu) and is found behind the dashboard glove box.

Modes of operation.

1. Normal driving mode: this is the normal operation height of the suspension
2.
Extended height mode: (user controlled), this is activated via a button on the dashboard. Activation/dis-activation comes with a dashboard light and audio chimes. This mode raises the back end for extra off road ground clearance.
3.
Dropped height mode:, (user controlled) this is for hitching a trailer or caravan and needs a remote key fob, although you can buy these keyfobs from ebay etc… This key fob accessory needs to be programmed to your car by a dealer. This mode drops the back end down below ‘normal’ operation levels.
4.
Grounded Chassis Mode: (automatic) this mode is automated by the SLABS ecu. If it detects that the chassis is grounded using the traction control sensors. It automatically raises the chassis beyond extended height temporally in an attempt to jack the chassis out of its grounded situation.
5.
Transport Mode: (dealer only) This is only available to a dealer or someone with a ‘testbook’ computer, it lowers the suspension right down, for use when the car is on a transporter.


Quirks and safety.

The suspension will rise about 20mm once the engine is started and all the doors closed. This is normal.
The suspension will drop about 20mm once the engine is switched off and all the doors are closed after exiting the car. You can usually see this happen and hear the air rushing out. This is normal.
The ‘extended mode’ will return to ‘normal mode’ once the car drives over 18mph. lights will flash on the dash and you will hear the chimes. This is normal.


For safety, all the doors including the bonnet and boot must be shut to allow any changes in the suspension height. (Remember this if you are making a repair!)


Troubleshooting.

Land Rover recommend that the air bags be changed every 5 years as they become porous with age – so if they haven’t been changed, change them..!

Sinking on one side or the other is a sure sign of an air leak on that side, if it regains normal height after running the engine (remember doors closed!) then the compressor is ok and you should be looking at replacement air bags. Replace them in pairs!
Spraying soapy water on them when in ‘extended height’ mode is a good telltale for an air leak. Find the bubbles and you have found the leak!
Expect to pay around £90 each for Air Bags and £0.50p for the clips – you’ll need two clips for each air bag. The clips are reusable, but may break when getting them off. Get some anyway to be sure.


Very few people have had an air pipe wear through by rubbing on the chassis, this is not a common fault. If this happens then the compressor will be constantly on (when the engine is running) and the car will not lift on that side.

Over inflation on one side or the other is a sign of a defective ride height sensor; this will pump the air bag to the max and will cause the front to dip down on the opposing side. DO NOT DRIVE THE CAR if this happens, Get it recovered and replaced immediately! Air bags have exploded due to over inflation. At any road speed this could be lethal... believe me, they go with a bang!!!
Replacing them is an easy job, but for safety sake must be done with caution given the fault. Expect to pay about £25 for a ride height sensor and a further hour or two costs for calibration at the dealer


Sinking on both sides and not able to regain height is probably a failed compressor or faulty valve block. Some people have claimed to source just the valve block, mostly the compressor and valve block come as one unit. The Compressor is very easy to change. Expect to pay about £200 for a new unit.

When attempting to do any repair on the suspension, pay attention to whether to support the chassis or the axle or both.



Replacing the compressor unit:

1. Secure and chock the car
2.
Jack the car slightly at the back and place axle stands under the chassis rails, taking the weight of the car off the axle.
3.
Locate the compressor and remove the cover using the two turn buckles and a penny.
4.
Undo the two bolts that hold the compressor to the chassis.
5.
Get a couple of house bricks or similar block of wood and place them under the compressor on the ground.
6.
lift the compressor unit as a whole onto the bricks (there should be enough slack in the pipe work)
7.
Undo all the electrical and pipe work connections and swap out for the new unit.
8.
Hook compressor back into place on chassis rail and bolt back on.
9.
Jack car and take axle stands away, remove jack.
10.
Spray soapy water onto the valve block to check for air leaks.
11.
Replace cover.


Inside the compressor unit:

compressor.jpg



Replacing an Air Bag

1. jack car really high put stands under chassis letting axle dangle
2.
remove jack and put under diff pan.
3.
take off wheel, jack axle slightly
4.
carefully take off two air bag retaining clips at mounting at top and remove air supply pipe.
5.
remove bag like light bulb
6.
lock new bag in
7.
use jack to raise axle and get pipe on.
8.
put clips back on
9.
jack up axle really high to fool sensors into low ride height
10.
close all doors including boot and open drivers window.
11.
start car through drivers window and run for a few seconds to put just a touch of air in the bag

12. stop engine and check that bag is inflating properly and square
run engine again till bag inflated

13. put on wheel
14. take off stands and jack


Replacing a faulty ride height sensor.
  • take your keys out of the ignition.
  • DO NOT RUN THE ENGINE until you have completed the job
  • if the car is up on one side due to over inflation, release air pressure at the valve block on the appropriate side by slowly slackening off the pipe union. DO NOT WORK IN THE WHEEL ARCH until correct ride height has been restored.
  • chock, jack, put chassis on stands and remove road wheel.
  • locate electrical connection on sensor and unplug, unbolt sensor and replace.
  • restore electrical connection
  • replace wheel
  • with all doors closed run engine and observe.
  • use a tape measure to compare sides, measure from the hub of the wheel to the top of the wheel arch. If it is wildly out, go see a dealer for a suspension calibration.

Converting the Air Bags to Coil springs.
There are conversion kits for about £100 to convert from Air to Coils.
Many people consider this option if the air is proving problematic.
Bear in mind the following if you are considering this…

  • The air suspension is a European Standard for a 7 seater, if you go to coils you may invalidate your insurance for a 7 seater.
  • The conversion to coils requires the re-programming of the SLABS ecu to turn off the air function, an additional cost at the dealer!





...thats about it

Congrats on an exceptionally thorough and helpful article.
My 2003 series 2 won't let go of off-road mode on the off side....should I be looking at blocked valves, or height sensors please ?
 

Congrats on an exceptionally thorough and helpful article.
My 2003 series 2 won't let go of off-road mode on the off side....should I be looking at blocked valves, or height sensors please ?


I would kindly suggest you both post iin the Disco section, also it would be benificail for you both to connect up to working diagnostics ( nanocom or Hawkeye if posssible ). This may help you resolve your problems in a more timely manner.

Cheers
 
Thank you all, I have fixed my car today, as someone mentioned in another post, I took out the relay from R3 (headlamp washer) , and put it into R5, sls… hew presto it worked all good.. so,then I went to lookers landrover dealer ship, and bought a correct relay for about £12 with tax...… ALL FIXED and happy bunny.
 
Something I didnt mention in detail when writing the original guide...

When replacing an Air bag, you can release air at the compressor end if it is easier for you. (look at the photo). each bag has its own independant feed. you can release air out of a bag by slackening off the union with the valve block.

It is also common for water to find it's way into the compressor through the intake pipe. although it is possible by removing the compressor to check the bore for the presence of water. this is no gurantee it will work again!
my god , this is an old post but cheers battenberg.... got to grind off a bolt tomorrow and take this pesky compressor off. got a service kit coming for it. got to dry this mother out, no doubt, and hope it works when i plug it back in
 
I replaced both my air bags today on my Discovery 2. Hopefully problem solved.
Definitely the drivers side bag was leaky as I had seen and felt the leak where the bag rolls over. The leaky bag usually needed a bit of weight before it would start to leak and drop down and most of the time it would come back up with the compressor if the weight wasn't too much.
What was confusing is that when the leaky bag had enough down weight to go down, the passenger side bag would let down as well, even though the weight was on the drivers side and I am quite sure that bag was not leaky.
I do not know what is causing that and I am pretty sure it never used to that, it usually dropped on drivers side only. Is the suspension trying to keep itself level on both sides or is there something else going on? I thought both bags were totally independent of each other?
The compressor still brings them both up.
I suppose time will tell.
Thanks so much for the original post - helped me a lot today.
 
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Hello Air Suspension Boffins. I am quite okay working on air suspension having played with HGV springs and I find the hydraulic suspension on older Citroens quite simple, so don't scare easily. I am investing the idea of putting air suspension on the front of my D2. It is my intention to use mostly genuine Land Rover parts for most of the system and control the valves and compressor using the information from height sensors with either a Raspberry Pi or an Arduino. I am not too concerned about being able to raise or lower it like the rear as I have yet to find the need to do this, just to allow it to adjust itself as needed.
Also, how do the height sensors work? Is it a variable voltage signal similar to a fuel gauge or did the boffins at Lode Lane make it overly complicated just because they could?
Regards

Trevor
 
Hi, awesome write up thankyou. Question part 6 on air unit diagram is the pressure regulator it has 2 settings. Any idea on the actual details of each please? You use an Allen key to turn and lock into each. I am guessing its a higher and lower pressure but which is used for what? Or just a simple harder or softer but ... harder would mean the bag is higher which I haven't noticed as have tried both settings
 
Hi folks. This is my first post on LandyZone. Thanks for the great info on the air suspension system. I have both bags fully lowered and will not rise, so I'm assuming that the compressor is the problem. Took me over a day to get the tray off the chassis. I had to destroy it basically because one of the bolts securing the tray to the chassis had ripped the threaded metal section of the tray lug out of the rubber housing, so it just kept spinning. Very little hiss from the compressor pipes when I released them after running the engine for a minute so probably the piston: I could hear it [I think] ticking constantly but no pressure to inflate. Just opened it up and it's lined with greasy soot. I'm guessing a recon unit would be the way to go rather than refurbing this one.

Other problem is that the bracket holding one ride height sensor had almost completely disintegrated so I'll have to try and fabricate a new one before I can fit the new sensors. Unlikely to find a scrapper I could cut them off in Spain. Anyone with any links to replacing this bracket, I'd appreciate it. Rebuilt a few Landys but this is a different kettle of fish: not sure I'm up to it or up for it.
TTFN
[NS]
 
I can vouch for the exploding air bag! Just parked the car in the garage, 5 minutes later and BANG! Looking on the bright side, the car was in the garage and not on the drive and now I don’t have to faff around depressurising the system!
 
Just had a bad day made worse as the rear suspention has sunk tried replacing the compressor with another spare I had and that did not pump properly either so had a cuppa and restarted by stripping down the compressor totally only to find that the scrubber filter was so wet in side the material in there was solid lump (what ever it is not sure )removed the mess and tried off the vehicle and guess what the pump has never worked so well . When back on my disco it pumped up so fast and back to how it should be , Had ret reset with my nanocom SORTED . It appears that moisture some in from the rear filter the 1 behind the ns lamp assy so I am going to resite it some where dryer
 
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