BMW M5 Competition (F90) Buyer’s Guide: What to Check Before You Buy

The F90-generation BMW M5 Competition is a masterclass in engineering, bridging the gap between a track-ready supercar and an executive saloon. With its 4.4-litre twin-turbo V8 (S63B44T4) pushing out 617 bhp through a highly sophisticated M xDrive all-wheel-drive system, it delivers devastating real-world performance.

However, running an elite performance vehicle comes with specialist responsibilities. While the F90 is widely considered the most mechanically robust M5 in generations, skipping due diligence can land you with main-dealer repair bills that quickly eclipse your initial investment.

If you are hunting for an F90 M5 Competition on the used market, this guide highlights the vital mechanical, structural, and electrical weak points you must check before signing on the dotted line.

1. The Engine Bay: S63 Twin-Turbo V8 Critical Checks

The S63 engine in the F90 is the most highly evolved version of BMW's hot-V V8. While remarkably reliable when maintained, it features a few known vulnerabilities that require strict physical and historical inspection.

The Hot-V Coolant Expansion Tank Leak

This is the single most common and dangerous fault on the F90 M5. The factory plastic coolant expansion tank is situated directly above the hot-V, where the two turbochargers generate extreme heat. Over time, this thermal cycling degrades the plastic seams, causing microscopic cracks.

• The Risk: Coolant doesn't just leak onto the floor—it drips directly down into the ignition coils and the fuel injectors for cylinders 5 through 8. If left ignored, the corrosive fluid destroys the injectors and can lead to engine misfires or total engine failure.
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• What to Check: Lift the carbon or plastic engine cover and inspect the lower seams of the expansion tank for white, powdery, or crusty dried coolant residue. Check the service history via the VIN to see if the upgraded, revised tank (part number ending in 9450) was fitted under BMW’s Technical Service Bulletin (TSB) or if the car is a post-2021 Facelift (LCI) model, which shipped with the corrected unit from the factory.
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[Factory Plastic Tank] -> Heat Cracks -> Leaks Onto Injectors 5-8 -> Misfire / Engine Damage

[Upgraded Revised Tank] -> Reinforced Seams -> Resolves Failure Risk ?

High-Pressure & Low-Pressure Fuel Pumps

Early production models (primarily 2018–2020) were subject to manufacturer recalls regarding the fuel delivery system. The low-pressure fuel pump (LPFP) software could cause the pump to stop unexpectedly, causing sudden stalling. Additionally, a separate recall addressed high-pressure fuel pump (HPFP) flanges that could crack and weep fuel.

What to Check: Request the vehicle's full digital service history printout from a main dealer or a verified independent specialist to confirm that all factory recalls have been signed off.

VANOS Solenoids & Maintenance Intervals

The variable valve timing system (VANOS) uses fine oil-ways and solenoids that are highly sensitive to oil quality. If a previous owner adhered strictly to BMW’s long-life 18,000-mile service intervals rather than shortening them, carbonised oil deposits can stick the solenoids, resulting in rough idling, hesitation, or a drivetrain warning light.

What to Check: Look for a history of mid-interval oil changes. For an M car of this caliber, oil changes should ideally occur every 6,000 to 10,000 miles or every 12 months.

2. Drivetrain & M xDrive System

The F90 was the first M5 to feature all-wheel drive. While it provides incredible traction, it places immense load on the transmission and transfer box.

Transfer Case Shudder

The M xDrive system utilizes an internal multi-plate clutch pack inside the transfer case to shift power between the front and rear axles. If the car has been driven aggressively with misaligned tyres, or launched frequently using Launch Control, these clutch packs can wear prematurely.

What to Check: During your test drive, find an open space, lock the steering to full click, and move forward slowly in both directions. Listen and feel for any "shuddering," skipping, or binding sensations. Any vibration during tight, low-speed maneuvers indicates a failing transfer case or heavily degraded actuator motor.
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ZF 8-Speed Automatic Transmission

Unlike its predecessor’s dual-clutch setup, the F90 uses a torque-converter ZF 8-speed automatic. It is fundamentally robust but demands smooth operation. Ensure shifts are imperceptible in Comfort mode and instant in Sport/Sport Plus. Any clunking under downshifts suggests a worn mechatronic unit or abused hardware.

3. Chassis, Carbon Ceramics, & Consumables

Maintaining an M5 Competition means accepting high consumable costs, but you must ensure you aren't inheriting a massive bill on day one.

4. Checklist for the Test Drive & Paperwork

• The Running-In Service: This is the ultimate test of an M car's history. BMW requires a vital running-in service at 1,200 miles to drop the factory break-in oils from the engine and differential. If this service was missed or completed late (e.g., at 3,000 miles), BMW can invalidate powertrain warranties, and it indicates negligent ownership.

• Modifications and ECU Tuning: The S63 engine tunes easily, but aftermarket maps place extreme thermal load on the turbochargers and fuel systems. Check if the ECU has been flashed. Look for telltale signs like aftermarket exhaust downpipes, non-standard intake filters, or missing engine bay heat shields.

• Electronics & Infotainment: The F90 is packed with complex systems, from the digital dashboard to the multi-contour massage seats. Ensure the iDrive system boots cleanly, the 360-degree cameras operate without flickering, and the head-up display aligns correctly on the windscreen.