BMW 3.0si
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.
Best E85 Formula: N52 Meets Soft Top
265 hp NA straight-six, deep bass down low, screaming crescendo above 6,000 rpm — roof down, one of the most emotional sixes of its era. Pure and direct.
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 7
The hydraulic pump for the Z4 E85 hood is mounted in a poorly protected position. Blocked drains allow water ingress; the pump corrodes and fails. Replacement is labour-intensive and expensive.
The electric power steering on the Z4 E85 occasionally fails — particularly on short-trip drivers as the battery becomes too weak. Steering angle sensor faults and column defects also occur.
The N46B20 four-cylinder in the 2.0i Z4 E85 suffers from premature timing chain wear due to a weak chain tensioner. Neglected oil maintenance causes the chain to elongate and can lead to engine damage.
Water enters through leaking tail lights or the boot vent. The expansion rivets on the tail lights become porous, seals age and allow moisture in. Can lead to short circuits and mould.
Ignition coil failures are a known issue on the Z4 E85, particularly at higher mileage. Oil from the valve cover gasket into the spark plug tubes is often a contributing factor. Multiple coils can fail in succession.
The sporty suspension setup on the Z4 E85 leads to above-average tyre wear, especially at the rear. Rear tyres can be at the wear limit after just 25,000 km. Broken springs have also been reported.
On the E85 Z4, the rain sensor and window regulator motors fail more often than usual. The rain sensor triggers in sunshine; windows move jerkily or not at all — both are age-related symptoms.
Reports & Tests
1161 owner complaints filed with NHTSA (2002–2008). Most reported: Steering (965), Airbags (86), Electrical (52).