Short answer: air spring, valve block or sensor, rarely the compressor

Quick answer first: a Range Rover sagging on one side overnight most often means a slow leak at that corner’s air spring, an internal leak in the valve block feeding that corner, or a faulty height sensor on that corner. Models affected include the L322, L405 and L494; original air springs on these cars commonly reach 70,000 to 120,000 miles before failure.

The compressor usually causes an even sag across all corners when it fails. If only one corner is low, suspect a local component; compressors more typically begin to struggle around 80,000 miles on older L322 units, where piston seal wear makes pump times much longer.

How the Range Rover air suspension works in plain terms

The system has four height sensors, four air springs, air lines, a central valve block and a compressor with a reservoir. Each corner sensor reports body-to-axle distance to the ECU; if a sensor fails or reads incorrectly the ECU can be convinced the corner is fine when it is low. JLR EAS systems on L322 and L405 use one sensor per corner and a multi-valve block that isolates corners.

Valve block faults, clogged solenoids or split lines allow the pressure at one corner to bleed away even while the compressor and reservoir remain healthy. That is why you can often start the car and see the compressor run for a short while as it corrects the visible drop, especially on models with a working reservoir.

Most common causes when your Range Rover is leaning to one side

Air spring failure: rubber bellows crack from age, heat or salt; expect originals on L322s to often need replacing by 100,000 miles. A torn bag will leak slowly overnight and let the corner sag.

Valve block or solenoid leak: internal seals, blocked ports or corroded electrical connectors cause one corner to lose pressure even when the compressor is nominal; valve block faults are common on Discovery 4 and L405 platforms.

Height sensor faults: a stuck or corroded sensor on the low corner reports incorrect geometry; sensors are cheap and quick to swap, and misreadings can also force the system into constant hunt mode.

Air line or connector split: road stone damage or chafing can split a hose at the wheel arch; a puncture in the line will mimic an airbag leak but is usually quicker to spot with a hissing test.

Practical, at-home checks you can do right now

Morning check: photograph or measure ride height on both sides with the car cold and parked on level ground; if the nearside is low after an overnight stand the leak is slow and local. This is especially useful on L322s where overnight sag is common.

Soapy water test: spray soapy water on the air spring, the air line joint and the valve block ports; bubbles mean a leak. Concentrate on the wheel-arch area and the line unions; faults here are often visible on the L405 and L494.

Listen and time the compressor: start the car and time how long the compressor runs to correct height. A working compressor that stops after 30 to 90 seconds suggests the pump and reservoir are OK; run times consistently over 2 minutes on an older L322 hint at compressor wear.

Fuse pull trick: inflate the car to height, then pull the air suspension fuse. If the low corner drops while the other corners hold height, the valve block or line at that corner is likely leaking rather than the bag.

When the compressor is actually at fault

Compressor failure usually shows as a general sag across both axles, a compressor that runs continuously or a compressor that struggles to build pressure from cold. On L322 examples with 80,000+ miles, piston seals and the motor often wear and the unit will run long and hot.

To confirm compressor health, watch pump time with the car cold and the reservoir empty, and check for fault codes with a JLR-capable scanner for codes like U0122 or B11C that can indicate communication or pressure issues. If the vehicle refuses to rise on start-up, or takes unnaturally long to reach height, treat the compressor as the primary suspect.

Repair choices: single air spring, axle pair or full set

Replace the failed part only when reasonable: if one bag has split on an L322 with 40,000 miles left on the others, fitting a single bag is practical. If the other springs are original and over 80,000 miles, replacing the pair on the same axle or all four avoids mismatched ride and repeated labour costs.

Valve block or line repairs are often quicker and cheaper than bags. Changing one solenoid or repairing a hose union on an L405 takes less time than replacing the bag, and is commonly completed within a single workshop visit. We recommend an OE-quality replacement bag for L322 and L494 models to match damping and longevity.

Labour times and what to expect

Typical labour for a single air spring swap is 1.5 to 2.5 hours on older L322 vehicles, and 2 to 4 hours on L405/L494 due to additional anti-roll and sensor geometry work. Valve block repairs or line swaps are usually under 2 hours.

If the compressor is replaced, allow 3 to 5 hours depending on access and whether reservoir plumbing needs renewal; always ask for a pressure test and a leak trace after fitting.

Risks of driving with a Range Rover one corner low

Short trips at low speed are manageable, but prolonged driving with a one-corner low condition accelerates tyre wear on the low side and increases load on that wheel’s bearing and suspension bushes. This is especially consequential on heavy models like the L405 and long-wheelbase variants.

A persistently sagging corner makes the compressor run more often as it tries to correct the imbalance, which can burn out the pump motor prematurely on compressors already past about 80,000 miles. Handling and braking balance are also affected, so avoid long journeys or high-speed driving until repaired.

Preventive maintenance to avoid the one-corner drop

Inspect bellows and lines annually after 50,000 miles, especially on L322s that see salted roads. Clean and protect height sensor pivots and electrical connectors yearly to prevent corrosion; a corroded sensor pivot is a common failure point on cars that have spent winters in cold climates.

If your vehicle is approaching 70,000 to 100,000 miles, budget for air suspension refreshes: replacing pairs or all four bags, renewing the valve block seals and testing the compressor will restore reliability and prevent inconvenient one-corner sagging.

Quick comparison: likely cause for a single-corner sag

Final Thoughts

A Range Rover sagging on one side is usually fixable without replacing the whole suspension; start with simple checks like a soapy-water test, listening for hissing and cycling ride height. Focus your attention on the bag, valve block and height sensor at the low corner, and only suspect the compressor when the whole vehicle is affected or pump times are abnormal. Early diagnosis saves tyres, bearings and wallet.