BMW M4
2,979 cc twin-turbo straight-six with closed-deck block and two mono-scroll turbochargers — BMW's first M engine with forced induction since the legendary M106. The block is significantly stiffer than the open N55 block and can handle cylinder pressures beyond 20 bar. Forged 42CrMoS4 steel crankshaft, Grafal-coated Mahle pistons in liner-free cylinders with LDS arc-spray coating — no liner, no sleeve. The sound divides the M community: under full throttle a deep, aggressive roar with turbo whistle on boost build-up, but miles away from the metallic naturally-aspirated shriek of the S65. In return the S55 delivers 550 Nm from 2,500 rpm that outpaces the S65 to 5,000 rpm. The hidden risk: the two-piece crank hub. On cars built before 03/2017 it can detach without warning — valve timing jumps, pistons hit valves, catastrophic engine failure. Affects 2–3% of all S55, but when it happens the engine is finished. Retrofitting a one-piece crank hub (€1,500–3,000) is the most important action. Second issue: plastic charge pipes burst under high boost — water from the intercooler can enter the intake and at 85,000 km cause a con rod failure. Aluminium upgrades are mandatory. Oil changes every 8,000 km with 0W-40; fit an oil cooler stone guard; check con rod bearings every 50,000–70,000 km. Those who observe these three points have an engine that lasts 200,000 km while tolerating 600+ hp via software.
M4 Cabrio: 431 hp open-air, 200 kg heavier
The M4 Cabrio trades roof rigidity for sun and S55 sound from above. Around 200 kg heavier than the Coupé — noticeable in fast direction changes and under braking. Barely slower on a straight line, but the character shifts from sports car to fast GT. With the roof open the twin-turbo I6 sounds noticeably more present.
Engine Weaknesses 10
Known issue on M3 F80 and M4 F82. Connecting rod bearings wear prematurely; preventive replacement every 50,000–80,000 km is widely recommended.
Symptoms: Knocking from the engine block, metallic particles in the oil, oil pressure warning
The multi-piece crankshaft hub is secured only by friction and can slip under load. Vehicles built before production date 3/2017 are particularly affected. Even minimal rotation misaligns valve timing — valve-to-piston contact and total engine loss are possible.
Symptoms: Usually no warning. Early signs: EML 'drivetrain error', rough idle, misfires, power loss under high load. Worst case: immediate total engine failure at high revs.
The exposed oil cooler (tube-fin design) hangs unprotected in front of the cooling pack and is frequently damaged by stone impact. Even small holes lead to sudden total oil loss and imminent engine damage.
Symptoms: Sudden oil pressure warning; visible oil trail under the vehicle; oil smell; often no gradual build-up — failure without warning
With axial bearing wear on a mono-scroll turbocharger, oil consumption can rise to 1 litre per 500 km. Cause: failed turbo drawing oil past the shaft seal. Regular oil level checks are essential.
Symptoms: Rapidly increasing oil consumption, bluish smoke under acceleration or at idle, power drop, whining turbo noises.
The plastic end tanks of the water-cooled intercooler become porous and allow coolant to escape. In the worst case water enters the intake tract — hydro-lock and engine damage are possible. Mainly affects 2016–2019. Aluminium upgrade recommended.
Symptoms: Warning 'charge air temperature high' or 'cooling system low'; coolant loss without visible external leak; misfires; white smoke
The standard plastic charge pipes between turbocharger and intercooler split at the flanges under boost pressure. Stock vehicles are rarely affected — the risk increases considerably with tuning.
Symptoms: Loud hissing on boost build-up; severe power loss; limp mode; fault codes P00BD/P00BF (mass air meter reading too high)
The mechanical water pump of the S55 wears under the high thermal demands of the twin-turbo engine. Thermostat and water pump should be replaced as a pair. A failed thermostat prevents coolant circulation — overheating at full load on a motorway can occur within minutes.
Symptoms: Coolant temperature fluctuates unusually, coolant warning under high load, faint whistling from engine bay, coolant loss without visible leak.
Wastegate flaps can rattle more on tuned S55 engines. Less common than on the N54 at stock power levels.
Symptoms: Metallic rattling on load changes, clattering on throttle application
The S55 cam cover gasket hardens through constant heat cycling and begins to weep from around 80,000 km. Oil drips onto the belt drive — a failed belt can cause consequential damage. Replace the spark plug tube seals at the same time.
Symptoms: Oil smell in engine bay after a motorway run, visible oil on the side of the cylinder head, oil patch on the underbody panel. In advanced cases light smoke.
The oil filter housing gasket leaks from 50,000–80,000 km — a persistent issue on all modern BMW six-cylinders. Oil pools beneath the housing and drips onto the undertray. The gasket itself costs under €30 but access requires removing the intake manifold.
Symptoms: Oil patch under the engine on the driver's side, oil smell on a hot engine, visible oil trace at the filter housing during an oil change.
Vehicle Weaknesses 6
The metal folding roof of the F83 M4 shows age-related hydraulic and sensor problems. Microswitches on the locking mechanism send conflicting signals and the system halts as a safety measure. In cold weather the roof often won't open.
The M-DCT GS7D36SG of the F83 wears clutch plates faster with frequent sport use. Transmission fluid changes every 40,000 km significantly extend service life. Mechatronics seals age over time.
The electric-hydraulic hardtop of the F83 M4 Convertible is susceptible to sensor and relay failures as well as hydraulic leaks. Water intrusion into the boot damages modules.
Blocked boot drain channels on the F83 M4 Convertible lead to water accumulation that damages expensive modules and the audio amplifier.
M performance brake pads on the F83 M4 with S55 turbo squeal heavily in cold and light braking. High wear under sport use. Many owners switch to more road-friendly alternatives.
The S55 M4 brakes with high-temperature pads squeal heavily during moderate braking. Design-related characteristic of the harder pad compound.
Reports & Tests
40 owner complaints filed with NHTSA (2014–2020). Most reported: Engine (16), Powertrain (14), Fuel System (7).