BMW M4 F83

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.

• !! Connecting rod bearing wear from 60,000 km

  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
  1,500–6,000 $
  Ad BMW S55 connecting rod bearingBMW M3 F80 LagerschalenBMW S55 connecting rod bearing
• !! Crankshaft hub slip (crank hub) from 60,000 km

  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.
  1,500–3,000 $
  Ad S55 Crank HubS55 crankshaftn Nabe11238604834
• !! Oil cooler damaged by stone impact from 40,000 km

  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
  600–1,800 $
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+ 7 more engine weaknesses + vehicle weaknesses