IsItAGoodCar
Reliability Guide

Common Problems with the
1999 Audi A6 Mk2 (C5)

We've identified 6 known issues that can affect the 1999 Audi A6 Mk2 (C5). 2 of these are serious faults that could be expensive to repair.

6
Known Issues
2
Serious
4
Moderate
0
Minor

All Known Issues

Blocked Plenum Drains

SeriousBodywork & Rust

Leaves and debris block the drains, leading to water entering the cabin and damaging the CCM.

Est. Repair Cost: £100–£800
Warning Signs:

Wet front carpets, Electrical behaving strangely

What to Inspect:
  • Feel the carpet in the front footwells
  • Check under the battery and plenum chamber for standing water or debris
Verified by IsItAGoodCar Research TeamUpdated

2.5 V6 TDI Camshaft and Rocker Wear

SeriousEngine

Early sliding-rocker versions can suffer cam and rocker wear. Later roller-rocker engines differ, so identify the engine code and valve gear before judging the risk.

Warning Signs:

Uneven running, Progressive loss of power or top-end noise

What to Inspect:
  • Request specialist valve-gear inspection if symptoms are present
  • Check correct oil specification and documented timing-belt work
Verified by IsItAGoodCar Research TeamUpdated
Official Recalls & Reference Documents:

Front Multi-Link Suspension Wear

ModerateSuspension & Chassis

The C5 uses a sophisticated aluminium multi-link front suspension with eight control arms per side. Bushings harden and ball joints develop play, causing clunks and vague steering.

Est. Repair Cost: £350–£900
Warning Signs:

Clunking over bumps, Imprecise steering, Uneven tyre wear

What to Inspect:
  • Listen for clunks over potholes
  • Inspect bushes and ball joints visually
  • Check for multiple suspension advisories on MOT
Verified by IsItAGoodCar Research TeamUpdated

Instrument Cluster Pixel Failure

ModerateElectrics & Electronics

The dot-matrix LCD in the instrument cluster loses pixels column by column, making the trip computer, odometer and warnings unreadable.

Est. Repair Cost: £100–£400
Warning Signs:

Partial or blank display, Hard to read fuel level or temperature, Trip computer unreadable

What to Inspect:
  • Check all displays during startup
  • Look for faded or missing pixel columns
  • Ask if cluster has been repaired or replaced
Verified by IsItAGoodCar Research TeamUpdated

ABS Module Failure

ModerateElectrics & Electronics

The Bosch 5.3/5.7 ABS control unit develops internal solder faults, triggering ABS and brake warning lights and sometimes causing speedometer dropouts.

Est. Repair Cost: £200–£500
Warning Signs:

ABS and brake warning lights, Speedometer dropping to zero, Three beeps on startup

What to Inspect:
  • Check dashboard warning lights
  • Scan for ABS fault codes
  • Ask if module has been rebuilt or replaced
Verified by IsItAGoodCar Research TeamUpdated

Driver Door Wiring Loom Breakage

ModerateElectrics & Electronics

Wires in the rubber boot between the body and driver door fatigue and snap over time, causing central locking, window and mirror failures.

Est. Repair Cost: £100–£300
Warning Signs:

Door window stops working, Central locking intermittent, Mirror adjustment fails

What to Inspect:
  • Inspect wiring in the door boot for broken strands
  • Test all door electronics
  • Check for previous repair work on loom
Verified by IsItAGoodCar Research TeamUpdated

Buying Tips for 1999 Audi A6 Mk2 (C5)

  • Check the front carpets for dampness (blocked plenum drains)
  • The multi-link front suspension is complex and expensive to refresh
  • 1.8T models need proof of regular oil changes
Check a 1999 Audi A6 Mk2 (C5) by Registration