BMW 645Ci
Same construction as the N62B48 with 4.4 litres and 333 hp — the workhorse of the N62 range. The Valvetronic eccentric shaft and intermediate levers carry the same wear pattern: from 150,000 km the intermediate levers machine into the bearing surface, misfires and Valvetronic limp mode follow. At idle a deep, dry V8 note; at revs increasingly silky overtones. Well maintained with short oil intervals a long-lived engine. Cooling system and valve stem seals follow the same rules as the big brother. A clean example with documented workshop history is money well spent.
The Sleeper Pick
The 645Ci is supposedly the base model E63 — but 333 hp NA with Valvetronic makes it a proper driver's car. Nearly as fast as the 650i, often a calmer service history when well kept, and the same V8 experience. Serious E63 shoppers should not overlook the 645Ci.
Engine Weaknesses 9
Rubber seals harden from ~130,000 km; oil passes the valve stems into the combustion chamber. Classic finding: blue smoke on cold start after standing. Special tool allows replacement without removing the camshafts.
Symptoms: Blue-white smoke from the exhaust on cold start and after idle periods. Increased oil consumption (0.5–1 L/1,000 km). No smoke when warm under load.
Aluminium pipe between the cylinder heads in the V seals with O-rings. These harden over time and coolant disappears without visible external leakage. Repair requires removal of the intake manifold.
Symptoms: Gradual coolant level drop without visible leakage. Sweet smell in the engine bay. Coolant warning light. In advanced stages risk of overheating.
The original plastic impeller can break at high mileage and spin freely — engine overheats without warning. Preventive replacement at 150,000 km with a metal impeller is recommended.
Symptoms: Engine temperature rises sharply and suddenly. Slight ticking at idle that disappears when driving. Coolant warning light. In extreme cases overheating damage.
Intermediate levers wear into the eccentric shaft bearing surfaces, mostly due to condensate in the oil from short-trip driving. Valvetronic enters limp mode; misfires on individual cylinders.
Symptoms: Misfires on cold start. Engine light. Power loss. Valvetronic limp mode with restricted drivability. Misfires are cylinder-specific.
The N62 has two electrically controlled thermostats. Failures cause the engine to run permanently cold or to overheat. Rarely a sudden failure — usually gradual.
Symptoms: Engine does not reach operating temperature or runs too hot. Heating works poorly. Increased fuel consumption. Coolant temperature fault code.
With long oil change intervals or short-trip driving, sludge builds up in the VANOS solenoid valves — camshaft adjustment responds sluggishly or not at all.
Symptoms: Rough cold start. Lack of power in the lower rev range. Engine light with camshaft fault code. Ticking noise on startup.
Rubber seal on the alternator bracket ages and leaks. Oil collects on the driver's side. Removal requires engine lifting — high labour cost for an inexpensive part.
Symptoms: Oil seeping from driver's side of engine bay. Oil spots under the car. Occasional oil smell. Oil can drip onto hot engine parts and smoke.
CCV membrane tears at high mileage; excessive crankcase vacuum pushes oil into the intake tract. Increased oil consumption also under load.
Symptoms: Strong vacuum when opening the oil filler cap. Oil in the intake tract. Increased oil consumption. Blue smoke even under load.
Check valve of the secondary air pump gives way, exhaust flows back and damages the pump. Engine light during cold start phase, no drivability fault.
Symptoms: Engine light after cold start. Noise from engine bay on cold start. No noticeable power loss. Fault often clears itself after warm-up.
Vehicle Weaknesses 9
The active steering (AFS) on the E63 can rotate the steering wheel up to 90 degrees and trigger uncontrollable steering reactions. When the AFS control unit fails, immediate workshop diagnosis is required.
The early iDrive system in the E63 is notorious for complete system failures. The controller, CCC head unit, and interconnections with other control units lead to expensive repairs when they fail.
The active DynamicDrive system on the E63 shows failures at higher mileages. The hydraulic roll stabilisation loses pressure or responds unevenly — a very expensive repair on the high-end suspension.
The N52/N53 petrol engines in the E63 are known for Valvetronic eccentric shaft failures and VANOS solenoid valve failures. Rough idle and difficult starting are typical symptoms of these expensive repairs.
On the N62 V8 (645Ci, 650i), valve stem seals harden from around 180,000 km. Oil enters the combustion chamber through the valve guides, causing blue smoke and high oil consumption.
The water pipe on the N62 V8 (645Ci, 650i) has a bonded seal that loses adhesion over time. The result is slow to sudden coolant loss — a known wear pattern on all N62 models.
The first-generation CCC iDrive control unit suffers from PCB thermal problems. It initially crashes sporadically (BMW logo boot loop) until it fails permanently. Since the CCC is the hub of the MOST ring, radio, navigation, and speakers all fail simultaneously.
Dirt and moisture accumulate under the plastic sill covers and cause unnoticed rust damage to the sills. The jacking points and the transition to the wheel arch trim are particularly affected.
The window anti-trap protection activates without cause when closing and reopens the window. Usually a worn plastic ring inside the window motor. Problem returns after reinitialisation.