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
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.
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).
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.
 |
 |
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. |
 |
 |
 |
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 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).
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.
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.
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
Page last updated July 2006