BMW 630i
The 258 hp top version of the N52 is one of the last large high-revving naturally aspirated engines from BMW: a magnesium-aluminium composite block that defines the class through extreme smoothness and a willingness to rev that drivers describe as 'like a sewing machine' — so even and effortless in its climb. Compared to the N54 turbo it sounds cleaner and more natural, without turbo hiss; instead a clear naturally aspirated note that fills out with increasing revs. Cold-start behaviour is impeccable; in daily use it runs nearly maintenance-free. Typical weaknesses: electric water pump (fails without warning, 80,000–150,000 km, preventive replacement recommended), Valvetronic eccentric shaft sensor (fault code, limp mode), VANOS solenoids with sludge build-up. Buying tip: check service history, as missed oil changes can permanently impair VANOS function.
NA Straight-Six Bliss
Last great BMW NA straight-six — deep rumble at idle, magnificent above 5,000 rpm.
Engine Weaknesses 5
The N52 electric water pump is a known wear item. When it fails the engine overheats quickly. Recommended: preventive replacement when any abnormalities appear or from around 100,000 km.
Symptoms: Coolant temperature gauge rises quickly, coolant loss, audible pump malfunction, engine overheating.
The gasket between the oil filter housing and the engine block ages and becomes porous, allowing oil into the coolant. Symptoms resemble a head gasket failure. Early replacement of both seals is recommended.
Symptoms: Oil film on the coolant; discoloured oil filler cap; coolant slightly foamy or brownish; no white exhaust smoke — a key differentiator from head gasket damage
The Valvetronic eccentric shaft sensor fails due to moisture and ageing. Fault code 2A31 is typical. The sensor costs approximately €275; installation requires opening the cam cover.
Symptoms: Rough idle; severe judder with light throttle input; increased fuel consumption (up to +30%); fault code 2A31; engine runs better with the sensor disconnected
The N52 magnesium cam cover has known sealing problems. Oil loss at the cam cover gasket, eccentric shaft sensor, and camshaft adjustment motor are common. Aluminium bolts must not be reused.
Symptoms: Oil loss at the cylinder head, oil smell, visible oil traces at the top of the engine, oil spots on the exhaust manifold.
The N52 VANOS solenoid valves block with oil sludge, particularly with long oil change intervals or short-trip driving. Cleaning is possible; a valve swap often suffices. Improved software from 2007/08.
Symptoms: Rough running; poor throttle response; rpm fluctuations at idle; warning light; camshaft phasing fault code; cold-start misfires
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.