Reliability Guide

Common Problems with the
1999–2001 Mercedes-Benz S-Class (W220)

We've identified 2 known issues that can affect the 1999–2001 Mercedes-Benz S-Class (W220). 2 of these are serious faults that could be expensive to repair.

Known Issues

Serious

Moderate

Minor

The 1999–2001 period has 1 more issue than the Mercedes-Benz S-Class (W220) average across all year periods.

All Known Issues

Biodegradable wiring harness insulation

SeriousElectrics & Electronics

Mercedes used a soy-based wiring insulation that degrades over time, exposing bare wires and causing short circuits, random warning lights and potential fire risk. Engine bay harnesses are worst affected.

Estimated cost: £500–£2,000Affects: 1998–2005Often appears around: Age-related

Typical symptoms

•Random dashboard warning lights
•Electrical gremlins
•Engine bay burning smell

What to inspect before you buy

✓Inspect engine bay wiring for crumbling insulation
✓Check for previous harness replacement
✓Scan for stored fault codes

Airmatic suspension collapse

SeriousSuspension & Chassis

The air springs and compressor degrade with age. Cars sag overnight, ride poorly and the compressor eventually burns out if leaks are ignored.

Most affected: Models with Airmatic

Estimated cost: £800–£2,500Affects: 1998–2005Often appears around: 60,000–120,000 miles

Typical symptoms

•Car sits low after standing overnight
•Suspension warning light
•Noisy compressor

What to inspect before you buy

✓Check ride height before start-up
✓Listen for compressor running excessively
✓Inspect for oil residue around air struts

Buying Tips for the 1999 Mercedes-Benz S-Class (W220)

✓Inspect the entire body for severe rust; the wheel arches, door bottoms, and boot lid are notorious for rotting badly due to poor factory paint.
✓Check the Airmatic or ABC suspension system; ensure the car does not sit low on one side, and listen for a strained compressor working overtime.
✓Verify the operation of the Sensotronic Brake Control (SBC) on pre-facelift cars; if the pump has reached its cycle limit, it will require an expensive replacement.
✓Test the COMAND infotainment and navigation system, as the units frequently fail and drain the battery while the car is parked.
✓Ensure the soft-close doors and boot operate smoothly; the pneumatic pump in the boot often burns out due to air leaks in the lines.
✓Check the front footwells for dampness; blocked reed valves in the scuttle panel will flood the costly SAM (Signal Acquisition Module) electrical units.