BMW M6
The S85 is a 5.0-litre V10 with ten individual throttle bodies and an 8,250 rpm rev limiter — Formula 1 technology in road trim. Above 5,000 rpm a shriek sets in that stands apart from everything else BMW builds. Naturally the engine needs care: con rod bearings should be preventively replaced every 80,000 km at the latest — with ACL bearing shells and ARP bolts; OEM is not an option here. Oil changes every 7,500 km with 10W-60 full synthetic, no compromises. The VANOS high-pressure pump in the oil sump is the second critical component: bearing failure leads to metal particles in the oil that contaminate solenoids and camshaft phasers. Regular oil analysis catches problems early. All ten throttle body actuators should be replaced as a set — individual replacement pulls the next one along shortly after. Those who take this seriously have one of the most emotional engines in BMW history.
Drive open, hear the V10
In the Cabrio the S85 sound comes through even more directly. Roof down, 6,000+ rpm, and the world becomes very small. Worst maintenance access in the model range, but the experience compensates entirely.
Engine Weaknesses 9
Standard connecting rod bearings with too-tight clearance (0.025 mm instead of the recommended 0.063 mm) wear prematurely through heat and high revs. Metal particles enter the oil and damage the VANOS pump and solenoids.
Symptoms: Knocking from the engine block, metal particles in the oil filter, VANOS fault codes, dropping oil pressure at high revs.
The pump bearing in the oil sump breaks at higher mileages. Gears shatter and metal fragments circulate in the oil circuit. In the worst case the camshaft phasers and timing chain are irreparably damaged.
Symptoms: Rattling from the engine block, VANOS fault codes 27B6/271A–271D, sudden power loss, MIL illuminates.
All ten individual throttle bodies have electric actuator motors with plastic gears that wear prematurely and overload the control board. Renew both banks simultaneously. Fault codes 2B15/2B16.
Symptoms: Sudden power loss, limp mode active, DSC and EML lights on, engine runs rough after about 5 minutes of driving.
Metal particles from connecting rod bearing wear settle in the VANOS solenoids and jam the valves. Often the first visible symptom of deeper engine problems. OEM part number 11367841072.
Symptoms: Engine stumbles at idle, power loss at low revs, VANOS fault codes, rough engine running.
The nitrogen pressure accumulator loses pre-charge and causes the pump to cycle every few seconds, wearing the pump motor prematurely. The pump motor alone is often sufficient. Part number for pressure accumulator: 23427567720.
Symptoms: Frequent short pump cycles every few seconds, jerky gearshifts, SMG warning in the instrument cluster, gear cannot be selected.
The four PCV check valves of the crankcase ventilation system block over time. Oil collects in the intake manifolds and is drawn into the combustion chambers. Increased oil consumption results. Inexpensive if caught early.
Symptoms: Oil consumption above 1 L/1,000 km, blue smoke on cold start, oil visible in intake tract.
Plastic impellers of the mechanical water pump disintegrate from around 80,000 km. Replace the thermostat at the same time. Miss this and overheating and expensive consequential damage to the V10 are the result.
Symptoms: Temperature gauge rises unusually quickly, coolant loss, overheating warning, power reduction through limp mode.
Ten cylinders mean ten coils and ten spark plugs. A single failure causes misfires and can damage catalytic converters. Complete set change every 30,000 km is recommended — mixing brands must be avoided.
Symptoms: Engine stumbling, rough running, MIL with misfire codes, increased fuel consumption, power loss at high revs.
With increasing age, cam cover gaskets and the rear crankshaft seal develop leaks. The V10 has two cam covers — labour is substantial, parts cost is moderate.
Symptoms: Oil smell in engine bay, visible oil traces on the engine block, oil spots on the parking surface after switching off.
Vehicle Weaknesses 6
The SMG III gearbox of the E64 Convertible has the same weaknesses as E63 and E60 M5. In the convertible, moisture ingress is an additional hazard.
Identical SMG-III problem as the E63: the clutch actuator leaks and contaminates the clutch disc with hydraulic fluid. In the M6 with 507 hp the clutch also wears quickly.
Hydraulics of the E64 convertible roof suffer from leaking cylinders and lines. Drain channels in the hood well become blocked with leaves and dirt.
The differential of the E64 M6 Convertible develops howling noise from worn bearings at higher mileage. The increased mass of the convertible places more load on the differential.
In the convertible the window glass guide is particularly stressed during hood opening and closing. Window regulators fail regularly.
The hood chafes against the rubber seal of the hood well at the C-pillar edge when folding. Hood and seal are damaged.
Reports & Tests
16 owner complaints filed with NHTSA (2006–2010). Most reported: Steering (6), Powertrain (3), Airbags (3).