2021 BMW M240i Problems: 7 Known Issues

On the 2017-2023 BMW M240i, the B58's engine oil filter housing doubles as an oil-to-coolant heat exchanger and is molded from polycarbonate rather than cast aluminum. Heat cycling and vibration embrittle the plastic, and the housing cracks or its gaskets harden so that coolant weeps past the internal coolant channel and engine oil seeps down the back of the block. Because the housing sits under the intake manifold on the M240i's longitudinal B58, the leak is usually only spotted as a slow coolant-level drop, an oily film on the underside of the manifold, or a burning smell after a drive. A class action filed in New Jersey on January 23, 2026 names B46, B48 and B58 engines in 2014-2021 BMW and MINI vehicles including the 2 Series, and alleges owners paid up to $4,000 for a part that should last 150,000 miles. Do not confuse this with the separate cylinder-head coolant vent-line service action: the brittle vent hose sits nearby and is a frequent misdiagnosis in both directions, so the actual leak point must be pressure-tested before parts are ordered.

On the 2017-2024 BMW M240i B58 3.0L Turbo I6, the B58 engine uses a plastic charge pipe to route compressed air from the turbocharger to the throttle body. Under sustained high boost conditions, the factory plastic charge pipe can crack, split, or blow off, resulting in an immediate and total loss of boost pressure. This failure can occur on completely stock vehicles as the plastic degrades from repeated heat cycling over time, but is accelerated by any ECU tune that increases boost pressure.

On the 2017-2024 BMW M240i B58 3.0L Turbo I6, the B58 engine's valve cover gasket is prone to degradation and oil leaks, typically developing around 60,000-100,000 miles. The rubber gasket material shrinks and dries out through repeated heat cycles, allowing oil to seep and eventually drip down the sides of the engine. In more severe cases, oil can leak into the spark plug tubes, causing misfires and potential ignition coil damage.

On the 2017-2024 BMW M240i B58 3.0L Turbo I6, the B58 engine's VANOS solenoid o-rings degrade due to wear and high temperatures, causing oil leaks and variable valve timing faults. When the o-rings fail, oil pressure to the VANOS system is compromised, leading to rough idle, reduced power, and check engine lights. This is a continuation of a problem that has affected multiple generations of BMW inline-6 engines.

On the 2017-2024 BMW M240i, the B58's solenoid direct injectors sit in the head behind Teflon sealing rings. As the seal hardens and the injector's internals wear, the injector either leaks down into the cylinder after shutdown or delivers an off-spec spray pattern. Owners report cylinder-specific misfires, a fuel smell at cold start, and rough idle for the first thirty seconds after a cold start that smooths out once closed-loop fueling takes over. Forum reports include an M240i failing an injector at around 78,000 km, and injector trouble on B48 and B58 engines has become common enough that it is now a routine independent-shop job rather than an oddity. Left alone, a leaking injector washes oil off the bore and dilutes the sump, which is what turns a modest part cost into a bottom-end problem - so a cylinder-specific misfire on a B58 should not be treated as a coil-and-plug job by default.

On the 2017-2024 BMW M240i, the M240i runs a two-pump fuel system - an in-tank low-pressure pump feeding a cam-driven high-pressure pump on the B58's head. As the HPFP's internal valve and cam follower wear, the pump can still idle and cruise normally but cannot maintain commanded rail pressure during hard acceleration. The DME sees the pressure deviation, cuts boost, and drops the car into limp mode with a Drivetrain Malfunction message - typically at exactly the moment the driver asks for full throttle. The tell that separates HPFP wear from an ignition or injector fault is that the fault appears under load and clears itself on restart, and that fuel-pressure live data diverges from the commanded value while codes alone look ambiguous. Tuned cars surface this earlier because a Stage 1 map asks for more fuel volume than a marginal pump can deliver, which is how it first showed up on M240i and M340i owners running higher-output maps.

On the 2021 BMW M240i, bMW opened a voluntary non-compliance recall effective July 15, 2021 covering 2021 vehicles built between November 23, 2020 and May 28, 2021, spanning BMW, MINI, Rolls-Royce and the jointly developed Supra, with 2021 M240i in the affected population. The safety belt retractors other than the driver's may not have been built to supplier specification: the Automatic Locking Retractor function can deactivate early and jam the webbing before it fully retracts, so a child seat cannot be cinched down firmly using the belt. The Emergency Locking Retractor function still locks in a crash and the LATCH lower anchors and top tether remain available in every affected car, which bounds the risk - but a parent who belts a child seat into a rear outboard seat of an affected M240i Convertible and cannot get it tight is looking at this defect, not at their own technique. Expected failure rate was stated as under 1%.