BMW 125i
BMW's first in-house four-cylinder turbo for the mid-size class. Timing chain and its guide rails are the main weakness — early replacement at any rattling noise.
Four-Cylinder Turbo
Turbo four with the notorious timing chain issue — capable, but the anxiety never fully goes away.
Engine Weaknesses 7
The best-known weak point of the N20. The timing chain and oil pump chain stretch; the chain tensioner fails. BMW offered an extended warranty (7 years/100,000 km) for pre-2015 models.
Symptoms: Rattling on start, engine warning light, sudden power loss, in extreme cases engine damage
The electric water pump fails, risking overheating. A BMW-typical problem across all engines with electric coolant pumps since the N52 generation.
Symptoms: Overheating warning, temperature gauge rises quickly, coolant warning
On the N20 the oil pump sprocket can wear prematurely or the oil pump chain can break. In documented cases (50,000 km) an internal drive component failure caused complete oil pump failure — catastrophic engine damage.
Symptoms: Whistling noise that increases with rpm; oil pressure warning; metallic rushing from the engine bay; unusual vibrations
The N20 exhaust camshaft adjuster wears internally and causes intermittent fault codes (130308). Cleaning the solenoid valve alleviates the problem; replacing the adjuster resolves it permanently.
Symptoms: "Drive power not available" warning message; intermittent power loss; fault code 130308; rough running
The oil filter housing rubber gaskets harden and become porous — coolant and oil can mix. Since coolant is routed through the housing, engine damage is possible if repair is delayed.
Symptoms: Oil film in the coolant reservoir, discoloured oil filler cap (milky), oil in the coolant expansion tank, oil streaks on the engine block below the filter.
The wastegate control solenoid develops adaptive learning faults and boost pressure regulation errors (fault code 123401). BMW-workshop repair requires cam cover removal and special tools — approximately 6 labour hours according to BMW.
Symptoms: Engine warning light, increased turbo rattle, fault codes 123401/1234131 (wastegate solenoid, learning-cycle error), no noticeable power loss in early stages.
The N20B20 can develop above-average oil consumption at higher mileages. Caused by piston ring wear and valve stem seals — particularly with extended oil change intervals.
Symptoms: Regular oil consumption above 0.5 L / 1,000 km, occasional blue smoke on cold start or after prolonged idling.
Vehicle Weaknesses 7
EPS issues are widespread on the F20: the rack binds, aluminium bolts corrode on vehicles built July 2011–May 2015, and the electric motor can detach from the rack. Full replacement usually necessary.
The EGR valve and EGR cooler can fail or leak on N47 and B47 diesel engines. In the worst case, coolant ingress can cause engine fire.
Water enters through displaced cable grommets, faulty door seals, or blocked sunroof drains. Problem occurs across all F20 production years.
On N13 and N55 engines, valve cover gaskets go brittle and the crankcase ventilation fails. Oil consumption rises to 0.5–1 litre per 3,000 km.
Shaft seals on the rear differential leak gear oil. Problem often appears as early as 25,000–50,000 km, especially on M135i and M140i.
Clattering rear axle caused by worn shock absorbers, known from production date 04/2012 onward. Dampers are regularly flagged at MOT. Track rod ends also wear prematurely.
The 6-speed automatic shows jerky shifts or delayed response — typical between 50,000 and 100,000 km. Software update on the gearbox control unit often helps.
Reports & Tests
160 owner complaints filed with NHTSA (2011–2019). Most reported: Airbags (85), Engine (24), Engine & Cooling (20).