Air Suspension Problems and Solutions
Operation, Faults, Diagnosis,
Field Recovery/Repairs (Classic, P38)



Main System Components and Failure Modes

Common Symptoms and Diagnosis
Leak Detection
Lowering to Bump stops when Parked
Frequent Compressor Operation
Frequent Short-Time Compressor Operation
Slow Pump up in Morning
Very Slow Pumping
Compressor Noise or Vibration
Compressor Failure
Spring Leaks (slow)
Leaks on Apparently Good Bellows
Spring Failure (sudden)
Leveling Problems
Continuous Compressor Operation
Sensor Out of Range

ECU/BeCM Reactions to Faults
Sudden Air Spring Failure
Sudden Air Loss

Field Recovery/Repairs

Depressurizing the System

Disabling the EAS

More Information
 

Main System Components and Failure Modes

An overview of the electronic air suspension (EAS) height settings and operation appear on the Range Rover Suspension page. Below we list the main components of the system as an aid in fault diagnosis, along with some notes on their failure modes. Information below on fuses, relays etc applies to the 4.0/4.6 models. More detailed specifics for the Mk III model appear in the Mk III Air Suspension operation, diagnosis and repair pages.


Common Symptoms and Diagnosis

Introduction:
Some faults are obvious and need little diagnosis. These include a blowout in an air spring or major leaks from any part of the system. This type of fault will generally happen suddenly and you will hear it and be able to localize the source of the leaking air by listening to it. In other cases faults may not be so obvious, and there are even examples of behaviour which appears faulty but is normal (see Range Rover 4.0/4.6 common problems and fixes).

"EAS FAULT" Message
The "EAS FAULT" message is displayed when any number of faults, such as the ones listed below, are detected by the system ECU.  As well as the message, all the lights on the height adjustment rocker switch start flashing and eventually settle into staying on, along with the "high" ride height indicator light. There are two degrees of severity of this fault condition:

1. "Hard Fault": If the fault is considered serious, the system goes into what we long-suffering owners call "Hard Fault" mode. It is accompanied by the vehicle lowering itself to the bump stops and displaying the warning not to exceed 35 mph.  Even if the cause of the fault is repaired, the hard fault condition cannot be reset without a visit to the dealer or other mechanic with the specialized T4/TestBook, Rovacom or Autologic test equipment. Most common causes are serious air leaks or compressor problems.
2. "Soft Fault": This is my own name for the less serious condition when the EAS FAULT message appears, accompanied by the Christmass tree lights on the dash, but not the the "25 MPH" warning.  The suspension can no longer be moved from the current height, but will continue to run the compressor and make adjustments. In this case you are lucky; if the cause of the fault goes away,  the fault clears itself when you switch off the engine for a while and restart it. In my experience and from other owner reports to datre, causes of this condition can include a bad EAS relay in the enine comparment fuse box, a bad ground somewhere in the EAS system, an intermittent electrical connecction, or a faulty height sensor.

Leak Detection:
A can of proprietary leak detector in a spray can can be purchased from the dealer, or you can put a home made solution of soapy water on the suspected spots (usually where the air lines enter and leave the valve block) and watch for bubbles. Some leaks are hard to find and and if you see cracks in at the bottom of the springs and you often find a corner low that you should probably replace the air spring. If you have a leaking spring, be careful where you park. Kevin Kelly notes that he pulled in to a parking space with the front spoiler over a cement planter. When air leaked out of his air spring he bent the plastic front spoiler as the weight of the truck pushed down on it.

Lowering to Bump Stops when Parked:
The ECU is not very intelligent when it comes to figuring out what is happening when the vehicle is parked. If the ground is anything other than perfectly flat, it will try to lower all the wheels to the height of the lowest one, rapidly resulting in the vehicle ending up on the bump stops. This rather unintelligent strategy is particularly annoying off pavement, since the ground there is nearly always uneven. So don't park where there is a big rock or other obstacle under the body of vehicle! If you want to stop in such a spot temporarily, either leave the engine running, or inhibit the system's unintelligent operation by leaving a door or the tailgate open or removing fuse F17 on the BeCM fuse box. See precautions above about being careful where you park.

Frequent Compressor Operation
Unfortunately this is usually normal. Partly it is due to the pressure switch being located on the valve block instead of at the tank. This causes the pressure switch to sense a drop in pressure every time air is drawn from the tank -- due to the long narrow gauge airline from tank to valve block. This momentary drop in pressure causes the compressor to come on again. If compressor operation becomes almost continuous, however, something is wrong -- see continuous compressor operation below.

Frequent Short-Time Ineffective Compressor Operation
If the pump runs with a short duty cycle, ie runs for a few seconds and stops, without effective pumping action, alert reader Hans Kroneman points out nthat it is most likely the EAS ECU cutting off the pump's power supply die to excessive electrical draw. The computer diagnostic systems often miss this fault. If you pull the pump relay and jumper the 30/51 pin to the 87 pin, the pump will resume running if this is the problem. The most common cause is the failure of the pump's rear bearing. A shortcut for fixing this problem is listed on the Falconworks site, and consists of drilling the brush holder from the rear bell of the motor, so the bearing can be cleaned or replaced and lubed, preloaded and staked back in so it will not shake itself loose again. If you try this, the four brush-holder retainers will need to be drilled on-center and tapped to #4x40 threads. Be sure to touch-up the solder joints on the back of the brush holder that were cracked by the armature flailing around, then refit it with new 4-40 screws. Falconworks advertises the ability to repair your EAS pump in this situation for about $100, depending on the level of damage, plus shipping.

Slow Pump-Up after Leaving Overnight:
In theory, even if the unintelligent ECU has lowered the vehicle to the bump stops overnight, the non-return valves in the valve block should ensure that enough air remains in the tank to pump it up again immediately in the morning. If this does not happen, and it takes ages for the system to pump up to normal height in the morning, air is probably leaking from the line from the tank to the valve block (usually at the connection to the valve block). If not, the valves inside the valve block are probably leaking; as of this writing there is no known solution for this other than to replace the $800 valve block.

Very Slow Pumping:
If the system takes a long time to recover after a couple of raising and lowering cycles, and there are no obvious air leaks bad enough to hear, the compressor may be getting worn out. It has a hard life, and is only an electric motor with a reciprocating pump attached after all. If this happens especially on cold mornings, one of the air springs may be worn out around the top or bottom (see below) and not seating properly. In this case it is best to drive off immediately and bounce around a bit, hoping the offending spring will seat itself (it usually does). If the system takes long enough to pressurize(more than about 10 or 15 minutes), the EAS FAULT message will appear and the system will go into hard fault mode, requiring a Testbook or equivalent to reccover from.  

Noise or Vibration from the Compressor:
After a while the air suspension compressor can get rather noisy due to the rubber mounts wearing out. A Service Bulletin (TEC600695, July 1995, "Electronic Air Suspension Compressor Noisy") recommends updating the compressor mounts with  2 STC 828 Rubber Mounts and 6 STC 3086 snubbing washers. I had this done on my 4.0 and it did quieten down the compressor. The new bushing design is better because it prevents the compressor mounting flanges sagging low enough to hit the mounting surface. Loose mounting nuts, can also lead to noise. Conversely, don't overtighten the nuts as the studs are just embedded in plastic and come loose, again causing vibration. If the noise is a kind of harsh rattle, the compressor is probably worn out and needs replacing or rebuilding.

Compressor Failure:
Complete failure of the compressor could be due to the failure of Fuse 44, Maxi Fuse 2, or Relay 20, all located in the engine compartment fuse box. The easiest way to diagnose the power flow is to unplug relay 20, connect its output socket to 12V and see if the pump runs. If so, the compressor itself is clearly OK, but the problem could be the relay or one of the fuses, the thermal cutout switch, the pressure switch or the ECU. For more compressor diagnostic information see the Compressor Diagnosis and Replacement page.

Intermittent compressor operation (or only operating for a small fraction of the time, resulting in very slow pump-up of the suspension) can be due to failure of its internal thermal cutout switch, which is designed to shut down the compressor when it gets too hot. In normal operation, the third lead on the compressor (which is internally connected to this switch) is grounded; when overheating, the switch opens. This happened on my 4.0SE; I was able to get the system going again by grounding this lead with a jumper. See the Compressor Diagnosis and Replacement page for more information, and the generic parts sources page for aftermarket replacement compressors.

Air Spring Leaks (Slow):
The rubber air springs do wear out faster than the old coil springs. One symptom is the boot popping out of position, especially in cold weather; I had this happen on leaving the car outside in the desert overnight, in access mode, and the suspension took a good 10 minutes to return to normal height on startup in the morning. The rubber boot seems to mate with the top metal part of the spring somewhat like a tire bead, and will usually reseat itself after a while. Michael Azzariti pressure tested an old air spring he replaced on his 95 LWB (see replacement procedure); he pumped 20 psi into it and put it into a bucket of water. Air seeped out from the top, between the metal and rubber joint. He tried a higher pressure and it sealed up (the pressure in actual use is up to 20 bar or 150 psi).

Another problem is plain old cracks and holes developing in the rubber when it gets worn. This happened on one of my rear springs around 60,000 miles. It developed a leak large enough that I could hear the air hissing out when parked in low profile. Since the spring had to be ordered from the UK, I had to drive it around like this for a couple of weeks. I was impressed that the system put up with this situation without shutting down and reverting to the "get you home" mode on the bump stops.

The following pictures illustrate some of the failure modes of air springs which develop slow leaks.  

front worn normal
Front spring worn extended



Close-ups of worn out front air spring in normal (above) and extended (top right) positions showing the perished, leaking rubber.


Photo at right also shows accumulated dirt on the piston which, if bad enough, can also cause a leak.


Photos courtesy of Graeme Cree.
Dirt on piston

Ron Beckett supplied the two pictures above of the air springs on his 4.6, clearly getting worn and soon in need of replacement. These are pix I took of the fully extended bags on mine last week.  But it wasn't where the bags were leaking - they were leaking about 1/3 up their length.  The leaks would come and go as the bag flexed.  Also it is probably possible for the rubber scale build-up on the lower aluminium bellows mount to prevent proper sealing. As a matter of interest Ron photographed the top and bottom of the worn spring bellows after removel (below).  

Bottom of the above air spring bellows (removed from Ron Beckett's RR). Note the rubber starting to split and crack.  The wear grooves may really be fold lines where the rubber has folded over.  Top end of same spring bellows.
This end is in perfectly good condition. 
An air spring whose rubber has begun to perish at a section that appears when the piston is about 1/3 into the spring -- ie probably the place of maximum wear.  Photo courtesy of Ron Beckett. 

Air Spring Leaks on Apparently Good Airbags:

Sometimes leaks can occur on air springs that do not appear to be worn out and have not undergone any trauma such as mine get subjected to off road by having sharp sticks poked into them. Ron Beckett reports such an experience: "One real odd thing about my EAS is that I was having intermittent loss of air and "kneeling" at the front right corner. I pulled the bellows off to replace it but was confused by the fact the the new bellows looked so different from the old ones. So I cleaned up the aluminium pistons and refitted the old bellows. The suspension hasn't sagged since - and that was in July 2003 - over a year ago!".

Air Spring Failure (Catastrophic):
Sudden failure of an air spring can occur due to spontaneous bursting or more likely being penetrated by some off road obstacle. I had the pleasure of this experience when my left front air springs got cut by a twig or other sharp object and burst (a loud gunshot like sound) while on a 4WD trail, 400 miles from home! Suggestions on how to deal with this situation appear below. 

Leveling Problems:
If the vehicle is down at one corner or side and there is no sign of air leaking, there is probably a bad height sensor or the system is out of calibration. The sensors are simple potentiometers (variable resistors). The front height ones on early 4.0/4.6 models can sometimes be knocked out of action just by getting water inside them. If bad enough this will generate a suspension fault code indicating that the sensor is out of range.

The system has to be calibrated after a sensor is replaced. Calibration can only be accomplished with the dealer's Test Book or equivalent (Rovacom or Autologic). Special spacers are placed between the axles and bump stops to achieve the correct height for each setting. NOTE: Because calibration is done in this manner, larger tire sizes do not cause a problem in the calibration process (initially I was worried that when the suspension was recalibrated it would be set to the same ground clearance as before, but this is not the case).  Standard ride height should be 790 mm from the ground to the top of the wheel arch.

Another potential cause of leveling problems is a sticky or inactive  valve in the valve block, or a fault in the valve block driver circuit.

Continuous Compressor Operation:
The compressor should shut itself off when it gets hot or when pressure reaches 10 bar (150 psi), but if it seems to remain on too much the first thing to check for is the presence of leaks (see above), most likely from the air tank connection to the valve block. Then, see if either the air compressor relay (Relay 20, Engine Compartment Fuse Box) or the pressure switch is stuck on (see the Electrical Troubleshooting Manual for details). Otherwise, the compressor may be simply worn out -- this does happen. Starting from a completely depressurized tank, the compressor should take about 6 minutes to recharge it. If it stays on long enough to overheat, its thermal switch sends a signal to the ECU which shuts it down for 3 minutes to cool off.

Sensor Out of Range
Some owners have reported the fault condition appearing after replacing the shocks or even jacking the vehicle up on a lift -- presumably the problem here is the axles moving outside the normal range causing a "sensor out of range" signal. If you are replacing the shocks, it might be advisable to disable the EAS and be careful not to move the axles to extreme positions. Another possible cause of this signal is a bad EAS ECU -- in 1998 thre was a Technical Service Bulletin, number 0007, "INCONSISTENT RIDE HEIGHT - ELECTRONIC AIR SUSPENSION (EAS)", admitting that bad ECUs were interpreting valid height sensor signals as outside range. The affected vehicles were in the VIN number range from VA 346794 to WA 409701. The remedy was to replace the ECU (part number RQT100040).
 

ECU/BeCM Reactions to Faults:

Minor faults like slow air leaks will not cause any warning messages to appear. When a more major faults, the EAS ECU is in league with the BeCM in plotting what to do. The following examples are based on my own experience. If you have experience with EAS faults, please write in and let me know so we can share your experience with others.

Reactions to "EAS FAULT" Message
When the dreaded "EAS FAULT" message appears, and the dash starts lighting up like a Christmas tree, I have experienced two types of reaction from the ECU.

1. "Hard Fault Mode": This usually happens when there is a serous air leak or compressor problems that stop the system getting up to pressure. It is indicated by the warning not to exceed 25 mph, and the vehicle lowering to the bump stops. The system is cleverly designed so that even if the cause of the fault (eg a blown air spring) is repaired, resetting the fault requires a trip to the dealer.
2. "Soft Fault Mode": This is my own name for the less serious condition when the EAS FAULT message appears, accompanied by the Christmass tree lights on the dash, but not the the "35 MPH" warning.  The suspension can no longer be moved from the current height, but will continue to run the compressor and make adjustments. In this case you are lucky; if the cause of the fault goes away,  the fault clears itself when you switch off the engine for a while and restart it. In my experience and from other owner reports to datre, this condition seems to be caused mainly by intermittent electrical faults, such as a bad EAS relay in the enine comparment fuse box, a bad ground somewhere in the EAS system, some other intermittent electrical connecction, or possibly a faulty height sensor.

Sudden Failure of Air Spring:
When my left front spring failed, I was off highway on a 4WD trail with the suspension in high profile and the transfer case in low range. Initially, the left front corner of the vehicle dropped and the system merely tried to level itself again. To do so it lowered the right front corner to the bump stops so it wa even with the left, but it left the rear up high, presumably thinking that on average the springs were at the right height! In this mode I was able to surmount the obstacles between us and the graded gravel road. As soon as we exceeded 35 mph, the ECU tried to get us out of high profile and realized something was amiss. It then announced "EAS Fault", lighting up the dashboard like a christmas tree and freezing up.

The rear was still high so the ride was not too hard, and we were able to drive the 450 miles home in this condition while keeping up with the traffic fairly well.

Sudden Loss of Air Supply / Very Slow Pressurizing:
If a leak is bad enough, or the compressor cannot pressurize the system after 10 or so minutes of trying, the ECU will again go into hard fault mode. This happened to me when on another off road expedition I ran over the accessory hose that I tapped into the air tank for airing up tires. Of course, the air quickly escaped from the tank. Next time the suspension tried to level itself again, no air was available and the usual "in process" blinking showed up on the height indicator display. If I had repaired the leak then, or disabled the suspension (see below), all would have been fine. However I waited too long and the ECU finally detected there was a fault after about 10 minutes or so of trying to pump up the suspension. Once in "hard fault" mode ("EAS FAULT" message on the message center, EAS warning light on, and all EAS lights lit up on the height control) the suspension froze up. I drove around for a while like this, but a few hours later on the freeway when I exceeded 70 mph another round of flashing lights and messages happened and the suspension went down to the bump stops, warning me not to exceed 35 mph (yeah right!!).

Air Suspension Field Recovery/Repair

Full details of how to restore operation in an emergency appear on the Field Recovery and Repair page. Information and links are provided on how to repair the problem causing the fault (eg replacing an air spring), how to restore normal ride height by pumping up the suspension manually if necessary, how to make field repairs to the compressor, how to use your notebook computer and free software to reset EAS fault codes, and a variety of other tricks that have been tried and tested by other owners.

Depressurizing the System

The manual advises depressurizing the system before replacing components such as springs. Their procedure for doing so requires the Test Book. However if you are in the field with a blown air spring, obviously the spring itself will already be depressurized. You can depressurize the air tank by SLOWLY unscrewing the drain plug -- it has a notch in the threads so when it is part way out it lets the air escape without firing the plug out like a bullet.

Disabling the EAS

For many repair operations you don't want the suspension to be adjusting itself up and down while you work on the vehicle. Classic air sprung models have a disable switch under the seat, but this is lacking on the 4.0/4.6. On these models, the following options are available for disabling the system:
1. Leaving a door or the tailgate open effectively freezes the suspension
2. Unplug the air suspension delay timer, a small black box that looks like a large relay under the drivers seat. See Air Suspension Disabling on the air spring replacement page.
3. Remove fuse F44 from the engine compartment fuse box.
 

More EAS Information

EAS Field Recovery/Repair
Replacing an Air Spring
Air Spring Replacement (Bladder Only)
Arnott Generation III Air Spring Upgrade: firmer on hwy, softer off road and more travel
Clearing EAS Faults with a Notebook Computer and Free Software
Compressor Diagnosis and Replacement
Compressor Rebuild Procedure
Compressor Field Repair / Temporary Rebuild
EAS ECU Interface and Connection Cable Details
Valve Block Details and Repair
Disabling the EAS
Emergency Bypass of EAS
Extended Profile Selector
Lifting the Air Suspension
Manual Pump-up of Air Suspension
Parts Sources for EAS Components
Range Rover Suspension Details and Mods
Range Rover III Air Suspension pages
Repair Details
Replacement with Coil Springs
Restoring Normal EAS Operation After Repairing the Cause of Fault Mode Onset
Sway Bar Disconnects
Low cost and generic parts sources (including suspension parts)

Airbag Man (Low cost Australian supplier of RR air suspension springs, compressors, parts. Worldwide shipping).
Arnott Industries (US makers of RR air springs and bladders)
Rover Renovations (US supplier of RR EAS parts, including compressor & valve block rebuild kits, air springs, air lines, etc)
Strutmasters (US supplier of coil conversion kits and replacement bladders)
Andy Cunningham's Air Suspension Operation Page
Andy Cunningham's Air Suspension Troubleshooting tips
ECU pinouts and diagram
Mechanical and Electrical Upgrades

 


 

 

 

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Page revised February 2, 2012