BMW M140i B58 F20

The B58 engine's oil filter housing module uses a small plastic coolant vent hose that connects to the expansion tank. After approximately 80,000-120,000 km, the intense heat cycles cause the plastic to become brittle and the rubber gaskets to harden. Symptoms include a sweet coolant smell after driving, slowly declining coolant level, and white crystalline residue near the filter housing. A permanent repair requires replacing the full OFHG gasket set, the plastic vent hose, and the single-use aluminum bolts simultaneously. Independent specialist cost is typically €600-900, while BMW dealers charge €1,000-1,500. A class action lawsuit was filed against BMW in early 2026 regarding this issue on B46, B48, and B58 engines, confirming how widespread it is. If ignored, low coolant can lead to overheating and serious engine damage.

The B58 crankcase ventilation (PCV) valve is integrated into the valve cover rather than being a separate part. The rubber diaphragm responsible for oil separation can tear or rupture, typically after 80,000-130,000 km. Symptoms include blue/white exhaust smoke, oil consumption increase, rough idle, and potentially limp mode. BMW issued a warranty extension (SIB 01 14 23) covering the PCV for 15 years/240,000 km from the original in-service date, so many M140i examples may still be covered. If out of warranty, aftermarket PCV diaphragm repair kits cost €50-150 and can be installed without removing the valve cover. Full OEM valve cover replacement at a dealer costs €800-1,200 including labor.

The VANOS solenoid O-rings are a common wear point on the B58. As the rubber O-rings age and harden, they allow oil to seep past, which triggers VANOS fault codes, rough idle, and reduced performance. This typically occurs after 80,000-100,000 km. The repair is relatively straightforward: the solenoids themselves cost approximately €80-100 each, and replacement takes about 30 minutes. Total professional repair cost is €200-500 depending on whether one or both solenoids need attention. Many M140i owners report this as a simple DIY fix.

Like most BMW engines, the B58 valve cover gasket degrades over time as the rubber compound hardens through repeated heat cycles. Oil begins to seep past the gasket, often visible as oil residue on the exhaust side of the engine. This typically appears after 80,000-120,000 km. The gasket itself costs €30-80, but labor is the main expense due to the components that need to be removed for access. Independent shops typically charge €400-600, while BMW dealers quote €600-900. This is a good time to also replace the PCV diaphragm if not already done.

The B58 turbocharger's electronic wastegate can develop a metallic rattle or buzzing noise, most noticeable at idle or very light throttle. This is caused by play in the wastegate actuator arm bearing. On many cars this is cosmetic and does not affect performance or boost control. The rattle tends to worsen gradually over time. If it becomes severe, the wastegate actuator can be shimmed or the bushings replaced for €200-400. In rare cases requiring turbo actuator replacement, costs reach €500-800. Many owners live with the noise as it has no measurable effect on engine performance.

The rear differential output bearings can develop wear over time, producing a hum or whine most audible between 3,000-4,000 rpm at steady cruising speeds, typically in fifth or sixth gear. The noise changes when lifting off the throttle. This is more common on RWD M140i models that have been driven hard. Many owners report driving 50,000+ km with the noise without further deterioration. However, leaving it too long risks damage to the more expensive ring and pinion gears. Bearing replacement costs €800-1,200 at a specialist, while a full differential rebuild runs €1,500-2,000.

BMW fitted a clutch delay valve (CDV) to protect the gearbox, which intentionally increases clutch plate wear to reduce gearbox stress. On stock cars, clutch life is typically 80,000-120,000 km depending on driving style. Tuned M140i models with increased torque can burn through a clutch much sooner. Symptoms include clutch slip under hard acceleration, a high biting point, or difficulty engaging gears. OEM clutch replacement costs €1,200-1,500 at an independent specialist. An upgraded clutch (Sachs Performance or similar) costs €1,500-2,000 installed and is recommended if the car is tuned. This only applies to manual gearbox cars.