BMW 320d
Revised M47 with more power and common-rail injection. Swirl flaps in the intake tract can stick and cause engine damage — regular inspection recommended.
Economy diesel
Frugal yes, fun no. The engine keeps up with traffic, but every overtake needs a run-up.
Engine Weaknesses 5
The timing chain can stretch or the chain tensioner can fail. Compared to the N47 the M47 is considered more robust, but timing chain problems occur at high mileages and with neglected maintenance.
Symptoms: Rattling on cold start from the front of the engine, easing after warm-up. With heavy stretching, engine damage through chain jump.
The metal swirl flaps in the intake manifold work loose through carbon deposits and can break off. An ingested flap blade causes immediate total damage to valves and pistons.
Symptoms: Engine stumbling, sudden severe power loss, loud metallic noise from engine, engine failure.
The aluminium cylinder head of the M47TU tends to develop hairline cracks between valve seats and glow plug bores at high mileages. The cause is the different thermal expansion coefficient of the aluminium head and cast iron block.
Symptoms: White smoke from exhaust, rising oil level through coolant contamination, coolant loss without visible leakage.
The turbocharger of the M47TUD20 is susceptible to damage through oil starvation or oil sludging. A blocked oil separator increases crankcase back pressure.
Symptoms: Whistling noise under acceleration, power loss especially at higher revs, blue smoke under load
The exhaust gas recirculation valve carbons up over time and no longer opens/closes correctly. The coking accelerates especially with lots of short-trip/city driving.
Symptoms: Power loss, increased fuel consumption, rough idle, fault memory entry EGR.
Vehicle Weaknesses 7
The plastic coolant expansion tank becomes brittle through thermal cycling and cracks or bursts — on almost every E46. A typical 3–4 cm crack appears along the housing edges. Risk of engine damage through overheating.
Rubber barrel bearings in the rear axle wear regularly. Repair requires full axle disassembly and special tools; Lemförder bearings recommended. Cost 400–630 € including wheel alignment.
The hydraulic bushings on the front control arms typically wear from 55,000 km. Wheel alignment is mandatory after replacement. Total cost 300–650 € depending on workshop.
The wheel arch liner wears through the primer at the inner wing seam. Rust grows from the inside and is only noticed once visible blisters appear. Welding repair is unavoidable.
The rubber O-rings in the VANOS unit become porous after around 100,000–165,000 km. The pistons then have excessive play, disrupting oil flow and camshaft timing.
The plastic sliders in the window regulator mechanism break almost universally. BMW doesn't supply sliders individually — only complete mechanisms. Cheap fix: aftermarket replacement sliders from third-party suppliers for a few euros.
Track rod ends wear as the joint grease dries out. Inexpensive replacement at around 100 € labour plus parts; always replace both sides and realign afterwards.