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HOW TO REPLACE AN AIR SPRING

HOW TO REPLACE AN AIR SPRING

by Alisdair Cusick, 20th October 2016

How to

Renewing Range Rover Classic/P38 air springs using low-cost software is a DIY job, with caution

An air spring is  probably the most likely item to cause a failure of the electronic air suspension (EAS) on a Range Rover Classic or P38. For anyone not familiar with EAS, a rubber bag pressurised with air replaces the steel coil springs between the axles and chassis. Air from the compressor, via the air tank, is regulated via the valve block supplying the air spring at each wheel, all controlled via measurements taken by the height sensor at each corner, and signalled to the ECU. 

The air spring assembly comprises three main components. The rubber sleeve (originally made by Dunlop) is the part which we are replacing here. The top plate closes the top of the sleeve and contains the air supply connection. The piston closes the bottom of the rubber sleeve, and the sleeve rolls over this as it extends and contracts in response to air pressure, thus raising or lowering the vehicle height and/or responding to road undulations. These constant height adjustments over the years slowly wear the rubber at the contact points and, combined with the ageing process of rubber, mean the springs can start to leak air. You’ll know if you’ve got a leak, because one end of the car will be lower down each morning compared to the rest. The air spring’s rubber sleeve folds over itself on the piston when compacted and, as this folded area wears, the cords inside the rubber can be exposed, by which time the component needs changing, regardless of leaks. It is still possible to buy rear springs for Range Rover Classics ready to fit with the upper and lower mounts already assembled to the rubber sleeve (or air bag) section. The fronts, however, seem on short supply or even out of stock.

Fear not, for the much cheaper air bag is available as a Dunlop item, so it is still possible to reuse the aluminium top plate and piston, and replace just the rubber sleeve. That’s what we’re showing here – fitting a new rubber sleeve to the front suspension, while retaining the existing top plate and piston. Replacing a rear spring is a similar operation, though as we said, they can be bought complete with the top plate and piston.

Equipping for the job You’ll need software to depressurise the air springs, and we’re using R Story Wilson’s EAS Unlock Suite (www.rswsolutions.com). This allows you to depressurise just the springs, separate to emptying the air reservoir itself. Please, never be tempted to do this job by cutting the rubber, or without fully depressurising first. The system works at 120 psi, and definitely has the potential for injury, even before you factor in the high pressure air taking with it a sharp blade or saw. The Range Rover Classic and P38 share almost the same system, so this task can also be applied to the P38, with some slight variations in fixings and software needed.

The basic principles though are common to both vehicles – as are the symptoms of a failed air spring. Aside from the pressure warning, my other tip is to point out that, on re-inflating, the system won’t fully function until the road wheel is in contact with the ground, and the axle stands are removed from the chassis. Only then will the springs fully inflate.

TOOLS:
8 mm spanner, flat screwdriver, EAS software and PC, EAS cable, vice, tyre levers, jack and axle stand


TIME: 2 HOURS | COST: £70.00

CONTACT: WWW.BRITPART.COM


1
STEP 1
STEP 1

REMOVING THE AIR SPRING ASSEMBLY: With the air suspension system set onto extended profile, crack off the wheel nuts and chock all wheels which will remain in contact with the ground.

2
STEP 2
STEP 2

Insert an axle stand under the appropriate chassis leg. I used two for safety, but it can confuse the system on re-inflation later.

3
STEP 3
STEP 3

Jack up the front wheel, and remove the road wheel. We’ll need the jack to alter the axle height at various points of the job.

4
STEP 4
STEP 4

Locate the EAS diagnostic socket, which is under the driver’s seat behind a kick plate. Fire up the PC, or your diagnostic tool.

5
STEP 5
STEP 5

Open the software, plug in the diagnostic lead, and switch the ignition to position ‘II’ which puts power to the EAS Electronic Control Unit (ECU).

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