BMW 640i
Single twin-scroll turbo instead of the N54's twin-turbo — torque comes in evenly from 1,200 rpm and doesn't let up to 5,500. At idle a deep, barely audible hum; under load a rich rumble that surpasses the N54 in refinement but lacks its rawness. Above 5,000 rpm the turbo drowns out the engine — those seeking naturally-aspirated emotion will be disappointed. Valvetronic almost completely eliminates the throttle butterfly; throttle response is therefore more direct than on most turbo engines. The electric water pump is the Achilles heel: fails between 80,000 and 120,000 km without warning. Valve cover gasket starts leaking from 100,000 km — replace the entire cover, not just the gasket. Oil changes every 10,000 km instead of BMW Longlife, 5W-30 LL-04. Tuning: Stage 1 brings 350+ hp; from Stage 2 the HPFP becomes the bottleneck — fit the B58 pump. Considered one of the most reliable M-engines of the last 20 years when maintained properly.
Six-Pot Coupe
Turbo R6 in the F13 — proper foundation for relaxed grand touring.
Engine Weaknesses 10
Connecting rod bearings wear with extended oil change intervals or oil starvation. Particularly affects vehicles on Longlife intervals driven hard.
Symptoms: Knocking from the engine block, oil pressure warning, metallic particles in the oil
The N55 electric water pump typically fails between 100,000 and 150,000 km. A sudden failure while driving can cause overheating damage to the cylinder head or gasket within minutes.
Symptoms: Overheating warning; cooling fan runs continuously or intermittently; slow warm-up; coolant loss at idle
Wide production variance in oil consumption. Some engines consume almost no oil; others up to 3 L/10,000 km. Piston rings and valve stem seals are the cause.
Symptoms: Frequent top-ups needed, blue exhaust plume when accelerating, oil level warning
The N55 VANOS solenoid valves block with oil sludge or become electrically sluggish. Metal wear particles from the engine settle on the magnets. Symptoms appear particularly in the lower rev range.
Symptoms: Rough idle after cold start; power loss below 2,000 rpm; engine warning light with camshaft control fault code; rpm fluctuations when pulling away
The CCV on the N55 is integrated into the cam cover. When it fails oil enters the intake tract. BMW only supplies the complete cam cover as a replacement part (~€400), making repair expensive.
Symptoms: Increased oil consumption; blue smoke after cold start; oil in the air filter box; rough idle; burning oil smell from the ventilation vents
The N55 is a direct injection engine without intake valve flushing. Carbon deposits form on the back of the intake valves over time. Less common than on the predecessor N54, but present from around 150,000 km.
Symptoms: Hesitation and misfires at certain rpm; power loss when cold; light smoke after extended standstill; increased fuel consumption
The N55 twin-scroll wastegate develops metallic rattling on cold start from bearing play in the exhaust housing. The noise disappears with throttle input — the turbo is functionally intact but the bearing housing is worn.
Symptoms: Metallic rattling or clattering after cold start that disappears immediately with light throttle; louder in winter; no power loss
The cam cover rubber gasket hardens and tears from around 100,000 km. Since the crankcase ventilation is integrated, experienced mechanics recommend replacing the complete cover rather than just the gasket.
Symptoms: Oil smell inside the cabin; oil seeping at the cylinder head edge; oil on the ignition coils; blue smoke at operating temperature; slight burning smell after driving
The N55 sump gasket becomes porous through thermal ageing after 5–7 years. The aluminium sump bolts add to the problem. Oil collects on the underbody and can smell strongly during throttle changes.
Symptoms: Oil drops under the vehicle; oil smell after spirited driving; oil film on the underside from front to back; oil level drops slowly
The N55 drive belt and tensioner pulley typically wear from 120,000–220,000 km. The tensioner is always replaced together with the belt. A snapped belt disables all ancillaries.
Symptoms: Squealing or whistling from the engine bay especially in the cold; noise when switching on the air conditioning; in severe cases loss of alternator and power steering
Vehicle Weaknesses 19
The auxiliary damper and its dust cover at the rear axle wear prematurely and become oil-soaked. As EDC dampers are only available as BMW originals (~1,800 € per side), repair is extremely expensive.
On diesel engines (640d), the EGR cooler can leak and lose coolant. Combined with soot deposits in the intake tract, glowing particles can form that may cause engine fire in extreme cases. BMW conducted a recall.
Identical issue to the F06/F13: the auxiliary damper and dust cover at the rear axle wear and become oil-soaked. EDC dampers are only available as BMW originals (~1,800 € per side).
On the 640d diesel (N57), the EGR cooler can lose coolant. Soot deposits in the intake can produce glowing particles, posing a fire risk in extreme cases. BMW has carried out recalls and service campaigns.
Both the N55 (640i) and N63 (650i) in the F12 are known for early electric water pump failures.
Same issue as on F06/F12: the auxiliary damper dust cover at the rear axle tears and EDC dampers become oil-soaked. Original dampers cost ~1,800 € per side; always replace in pairs.
On the 640d (N57), the EGR cooler can lose coolant; soot particles in the intake can create a fire risk. BMW has conducted service campaigns and recalls.
N55 (640i) and N63 (650i) in the F13 coupé are known for electric water pump failures. Possible from 100,000–150,000 km.
The standard rear air suspension suffers from porous air bellows that lose pressure. If not caught in time the compressor overloads and fails too. Complete system failure can cost 5,000–8,000 €.
On diesel variants of the G32 (630d, 640d), the EGR cooler can leak and lose coolant. BMW has conducted multiple recalls and service campaigns (extended through to 2022).
The frameless windows on the F13 coupé tend to produce wind noise, especially at the driver's door from around 130 km/h. New door seals and window guides help.
The N63 in the 650i F13 suffers from elevated oil consumption caused by porous valve stem seals, resulting from the extreme heat of the hot-V turbos.
The optional panoramic glass sunroof has 4 drain channels that block with leaves and dirt. Water then runs into the cabin blower or reaches the boot.
The optional dual-axle air suspension with adaptive dampers shows similar problems to the F series: dampers become oil-soaked, fault codes appear.
The frameless door windows on the Gran Coupé tend to produce wind noise at the driver's door from around 130 km/h. The window seals don't sit flush due to minor body flex.
The NBT infotainment system crashes sporadically and restarts. Stability deteriorates especially after smartphone OS updates. A vehicle software update usually helps.
On older examples seat rails loosen, causing rattling and movement in the seat. The frameless doors allow torsional forces on the body that cause creaking.
The NBT infotainment system restarts sporadically or permanently shows the boot screen. Bluetooth/USB stability deteriorates especially after phone OS updates. A BMW software update usually helps.
The G32's power tailgate can be disrupted by faulty spindle drives. After drive replacement, the tailgate control unit must learn the new position.