2014 — 2020
3.0L S55B30 TwinTurbo (M4)
Petrol
Test drive task: Gently accelerate in a higher gear at lower RPM to listen for any rhythmic clicking or vibration from the rear end. | Note: This is a good way to check for play in the driveshaft or differential bushings, which can occasionally show wear in high-performance models.
Check this by: Cold starting the engine with the bonnet open to listen for a brief rattle from the turbochargers or exhaust flap actuators. | Note: It is common for the wastegate actuators to develop slight play over time, which may be worth noting for your mechanic during an inspection.
While driving: Perform a few low-speed maneuvers with the steering locked in both directions. | Note: This helps ensure the steering rack and electric power steering components are operating smoothly without binding or unusual clicking noises.
Check this by: Reviewing the service history for consistent oil changes every 10,000km rather than relying solely on the onboard computer. | Note: Frequent oil changes are a common best practice for the S55 engine to ensure the longevity of the turbochargers and the complex VANOS system.
Usually time to inspect suspension bushings and coolant hoses for signs of age-related degradation.
Consider having the spark plugs replaced and checking the health of the crank hub bolt, which is a known point of discussion in the community.
A sensible time to ensure the water pump and auxiliary belt components have been inspected for peace of mind.
Prioritise a full pre-purchase inspection from a specialist who knows the S55 engine platform intimately.
Verify the service book shows consistent history with high-quality, manufacturer-approved synthetic engine oil.
Check all cooling system connections for signs of minor coolant weeping, which can be standard in cars of this age.
Ensure the dual-clutch transmission (if applicable) engages smoothly in both auto and manual modes without hesitation.
Monitor the tyre wear patterns to ensure the alignment is set correctly, as the S55 produces significant torque that can accelerate wear.
Estimated repair costs if issues arise
While not a guaranteed failure, the crank hub on the S55 engine is a frequent topic of discussion. If you want peace of mind, you might eventually need to budget for a preventative capture plate or hub upgrade.
The S55 uses a complex cooling setup with multiple radiators. As the vehicle matures, it is common to consider refreshing the water pump and expansion tank to avoid future overheating.
Given the performance nature of the 4 Series, the braking system is a wear item. Depending on the car's driving history, you should factor in a set of high-performance pads and rotors eventually.
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Disclaimer: This report is generated with the assistance of AI analysis based on verified automotive data. While we strive for 100% accuracy, enthusiasts should always conduct physical inspections and consult service records. View Full Disclaimer