The last rear-wheel-drive BMW 1 Series and the only one with a straight-six engine under the bonnet. The B58 3.0-litre turbo delivers 340 hp through either a 6-speed manual or the smooth ZF 8HP50 automatic, with optional xDrive all-wheel drive. Produced for just three model years (2016-2019), the M140i has developed a strong following as one of the best driver-focused fast hatchbacks of its era.· more· less
Plastic coolant vent hose and OFHG gasket degrade from heat, causing coolant loss around 80,000-120,000 km · more· less
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 US class action complaint filed in January 2026 alleges the defect on B46, B48, and B58 engines; that is an allegation at this stage, not a measure of how widespread the problem is. If ignored, low coolant can lead to overheating and serious engine damage.
PCV diaphragm failure (valve cover)
€150 - 1,2002 of 7
Rubber PCV diaphragm inside the valve cover tears over time, causing oil smoke and rough running · more· less
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 of North America extended component coverage for the PCV to 15 years/240,000 km under SIB 01 14 23, but that extension lists North American models and does not include the F20/F21 M140i, so this is a repair the owner pays for. 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.
VANOS solenoid O-ring deterioration
€200 - 5003 of 7
Variable valve timing solenoid O-rings harden and leak, causing rough idle and fault codes · more· less
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.
Valve cover gasket oil leak
€400 - 9004 of 7
Valve cover gasket degrades from repeated heat cycles, allowing oil to weep onto the exhaust side · more· less
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.
Wastegate rattle at idle
€200 - 8005 of 7
Electronic wastegate actuator develops play, creating a metallic rattle at idle and low throttle · more· less
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.
Rear differential bearing wear
€800 - 2,0006 of 7
Output bearings in the rear differential develop a whine at cruising speed, typically after 100,000+ km · more· less
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.
Clutch wear (manual gearbox only)
€1,200 - 2,0007 of 7
The 6-speed manual clutch wears faster than expected, especially on tuned cars · more· less
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.
Reliable for a performance car, but coolant system needs watching
The B58 engine in the M140i is widely regarded as one of BMW's most reliable modern engines, and high-mileage examples with 200,000+ km exist without major powertrain issues. The main concerns are the cooling system weak points (OFHG and vent hose) which are a known design weakness across all B58 applications, and the PCV diaphragm, which is a repair the owner pays for here, since BMW's warranty extension for it lists North American models only. The ZF 8HP automatic is extremely robust, and even the 6-speed manual is dependable when not abused. With proactive maintenance and regular coolant level checks, the M140i is a rewarding long-term ownership proposition.
Service history
Complete BMW dealer or specialist records essential. Verify oil changes were done at maximum 15,000 km intervals, not BMW's 30,000 km longlife recommendation.
Tires
Check tread depth, age (date codes), and uneven wear. Rear tires wear faster on RWD models. Look for signs of aggressive driving.
Cold start
Start the engine completely cold. Listen for any unusual rattling, knocking, or metallic sounds in the first 30 seconds.
Test drive
Minimum 30 minutes including motorway speeds. Pay attention to gearbox smoothness, any vibrations, and rear-end noises at steady cruise.
Specific for this vehicle
Check coolant level and condition
Low coolant is the most common B58 issue. Check the expansion tank level and look for white crystalline residue around the oil filter housing area.
Inspect for oil leaks around valve cover
Look at the exhaust side of the engine for oil residue. Check the valve cover gasket area and the oil filter housing gasket for seepage.
Listen for wastegate rattle at idle
With the engine idling, listen near the turbo area for metallic buzzing or rattling. Light rattle is common and cosmetic; loud persistent rattle needs attention.
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Check for exhaust smoke on acceleration
After the engine is warm, accelerate hard and check the rear-view mirror for blue or white smoke, which indicates PCV diaphragm failure or oil consumption issues.
Test clutch operation (manual only)
On manual cars, check the biting point height and test for clutch slip in third gear at low rpm under full throttle. A high biting point or slip indicates wear.
Listen for rear differential whine
At a steady 80-100 km/h in a high gear, listen for a hum or whine from the rear. Lift off the throttle to see if the noise changes. Differential bearing wear produces a constant hum that varies with speed.
Recalls and Technical Service Bulletins
Takata airbag inflator replacement (various production dates)Verify completed
Starter motor electrical overheating, fire risk (campaign 0012560600 / SR/03830/25, opened 23 September 2025, for F20/F21 1 Series built 28 September 2015 to 7 September 2021)Verify with VIN
Contact a BMW dealer with the VIN to establish which campaigns apply to the car and whether they have been completed. The starter motor campaign opened in September 2025 and covers a wide build window, so applicability is decided by VIN rather than by model year. SIB 01 14 23 is often quoted for this car, but it is a BMW of North America component warranty extension rather than a recall or service action, and the models it lists do not include the F20/F21 M140i.
Warranty Status
Factory warranty2 years with no mileage limit (in Germany a third year from Nov 2016 under the 2+1 programme); expired on all M140i models
Rust perforation warranty (12 years)May still apply on 2016-2019 cars
All M140i models are outside their original factory warranty. The 15 year/240,000 km PCV valve cover coverage under SIB 01 14 23 is a BMW of North America component extension and does not list the F20/F21 M140i, so budget for that repair yourself. Recall work itself stays free of charge whatever the car's age, so verify campaign status with the VIN.
Sources: Research draws on model-specific owner forums and owner communities, recall information from official authorities, German automotive press, and multiple workshop cost references cross-checked against each other.
This report is for informational purposes only and does not constitute professional advice. Estimates may be inaccurate. Always have a qualified specialist inspect the vehicle before purchase. We accept no liability for decisions made based on this information.
