48V Belt-Starter Generator (BSG) Failure
SeriousElectrics & ElectronicsThe Continental BSG power transistors overheat and fail, causing the 48V system to shut down and eventually leaving the car stranded.
Est. Repair Cost: £0 (recall) – £2,500
Reliability GuideCommon Problems with the
Common Problems with the
2018 Audi A8 Mk4 (D5)
The launch year brought Audi's most complex flagship with dual-touchscreen MMI and 48V mild-hybrid as standard. Early 2018-2021 cars carry a known BSG failure risk — the recall (27BQ) is essential and should be verified before purchase.
What changed for 2018
- •Launch with 3.0 TFSI and 4.0 TDI engines
- •Standard 48V mild-hybrid system
- •Dual-touchscreen MMI with haptic feedback
Common MOT watch-outs
- !48V BSG failure leaving car stranded
- !Air suspension strut leaks
- !Dual MMI screen freezes and reboots
4
Known Issues
2
Serious
1
Moderate
1
Minor
All Known Issues
Air Suspension Strut Leaks
SeriousSuspension & ChassisThe standard adaptive air suspension develops leaks over time, causing uneven ride height and expensive compressor replacement.
Est. Repair Cost: £800–£3,000
Dual-Touchscreen MMI Freezes
ModerateElectrics & ElectronicsBoth the upper and lower MMI screens can freeze, go black, or reboot, affecting navigation, climate and seat controls.
Est. Repair Cost: £0–£2,500
Software and Vehicle Management Glitches
MinorElectrics & ElectronicsThe extensive software architecture can produce phantom warnings, driver-assistance calibration issues, and infotainment bugs.
Est. Repair Cost: £0–£500
Buying Tips for 2018 Audi A8 Mk4 (D5)
- ✓Verify service campaign 27BQ has been completed via VIN before viewing
- ✓Check both upper and lower MMI screens for lag
- ✓Air suspension must sit level after standing overnight