BMW M850i
Third-generation hot-V eight-cylinder — electric wastegates, 350 bar injection, forged internals. In Sport mode a rich V8 growl with turbo hiss; in Comfort barely audible. Throttle response noticeably more direct than TU/TU2 thanks to electric wastegates. The most reliable N63 variant, but the hot-V architecture remains: short oil change intervals (max. 8,000 km) with 0W-40 are mandatory, not an optional extra. Valve stem seals and timing chain guides remain as residual risk at high mileage.
Gran Coupe — V8 in a Four-Door Wrapper
M850i Gran Coupe: 530 hp V8 with four doors and a big boot. Less emotional than the coupe or convertible — the four-door format waters down the GT character. Need V8 and space? The M550i is the more honest choice.
Engine Weaknesses 5
The fundamental design with valve stem seals is retained. At very high mileages (>150,000 km) and aggressive use the seals can suffer thermal wear. Repair costs €3,300–3,800 (approx. 6–8 hours' work, engine removal required).
Symptoms: Increased oil consumption at very high mileages, slight blue smoke on cold start or after extended standstill, oil deposits in the exhaust
The plastic timing chain guide rails are sensitive to degraded engine oil. Extended oil change intervals (BMW Longlife) accelerate degradation. Complete engine removal (~40 labour hours) required; preventive replacement at >150,000 km is advisable.
Symptoms: Rattling on cold start, engine warning light, occasionally loud clattering with heavily degraded oil
The hot-V design also generates residual heat in the turbo oil feed lines after shutdown in the TU3. Immediate shutdown after full-load driving causes carbon deposits in the oil lines. Cases with fully coked lines at 60,000 km have been documented.
Symptoms: Power loss under load, occasional turbo whistling, in extreme cases blue smoke after a motorway run
350-bar direct injection without intake valve flushing — carbon deposits on intake valves are inevitable even in the TU3. Walnut blasting every 60,000–80,000 km is recommended; cost €400–900.
Symptoms: Power loss at part throttle, occasional rough idle, increased fuel consumption
The TU3 generation uses a separate cooling circuit for the turbochargers. Coolant loss documented at 14,000–15,000 km, often without visible leak. Turbo coolant hoses under the covers are a frequent leak point.
Symptoms: Coolant warning light without visible puddle, periodic coolant loss, coolant smell after shutdown
Vehicle Weaknesses 5
xDrive transfer case requires correct oil specification and regular maintenance. In case of damage, extremely high repair costs.
iDrive 7 system freezes or shows a black screen. Additionally, horizontal lines on the zone LCD documented.
Adaptive shock absorbers can lock at maximum damping hardness through wiring faults or sensor defects.
Identical to G15: M Sport brakes squeal consistently when braking. BMW rates it as normal.
High torque from the S63 V8TT leads to premature inner edge wear. The Gran Coupé's additional weight worsens the situation.
Reports & Tests
5 owner complaints filed with NHTSA (2019–2026). Most reported: Cruise Control (2), Electrical (1), Engine (1).