The F90 M5's S63TU engine is a masterpiece when healthy but notoriously fragile under stress. Rod bearing failures and cooling system issues dominate the common-problem list, with catastrophic engine damage possible if warning signs are ignored.
Rod Bearing Failure (S63TU)
Occasional · high severityTypical onset: 40,000-80,000 mi
Symptoms: Metallic knocking at cold start that fades when warm, Metal flakes or glitter in oil during changes, Low oil pressure warning at idle, Sudden catastrophic engine failure if ignored
Fix: Engine-out job requiring complete lower-end teardown. Replace all rod bearings, mains, and thrust washers. Often find crank damage requiring machining or replacement. 25-35 labor hours depending on crank condition.
Estimated cost: $8,000-15,000
Transmission Oil Cooler Leak
Common · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Red ATF puddles under engine bay, Low transmission fluid warnings, Burnt transmission smell after spirited driving, Harsh shifting when fluid runs low
Fix: External cooler lines crack at crimps or cooler itself develops pinhole leaks. Access requires front bumper removal and partial undertray work. 4-6 hours labor plus fluid flush.
Estimated cost: $1,200-2,200
Turbocharger Wastegate Rattle
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Metallic rattle at idle or light throttle, disappears under load, Rattling most noticeable when engine is hot, No performance loss initially, Can lead to boost control issues if bushings disintegrate
Fix: Wastegate actuator arms wear bushings and develop play. Turbo removal required for proper repair or replacement. 12-16 hours per side, often do both. Some attempt in-situ bushing kits with mixed results.
Estimated cost: $4,500-8,000
Crank Hub / Harmonic Balancer Failure
Rare · high severityTypical onset: 70,000-120,000 mi
Symptoms: Rough idle with visible serpentine belt wobble, Accessory belt throwing or shredding, Crank position sensor codes (P0016, P0335), Severe vibration at all RPM ranges
Fix: Crank hub separates from damper or keyway shears. Requires front-end disassembly, potential timing chain work if debris entered system. 8-12 hours if caught early, 20+ if timing components damaged.
Estimated cost: $2,500-6,000
Transmission Mount Failure
Common · low severityTypical onset: 40,000-70,000 mi
Symptoms: Clunking on aggressive shifts or launch control, Excessive driveline lash when reversing direction, Vibration felt through shifter or center console, Visible tears in rubber isolators
Fix: Hydraulic transmission mount degrades from heat and performance use. Straightforward replacement from underneath, no subframe drop needed. 2-3 hours labor.
Estimated cost: $800-1,400
Cooling System Expansion Tank Cracking
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Coolant weeping from tank seams, especially at neck, Low coolant warning after heat cycles, Pressure loss leading to overheating in extreme cases, Visible coolant residue on tank exterior
Fix: Plastic expansion tank develops stress cracks from heat cycling and pressure spikes during track use. Easy access, 1.5-2 hours including system flush and bleed. Replace cap and hoses while there.
Estimated cost: $600-1,000
High-Pressure Fuel Pump Failure
Occasional · medium severitySymptoms: Extended crank time before start, especially when hot, Misfires under heavy load or high RPM, Fuel pressure low codes (P0087, P228C), Limp mode activation during hard acceleration
Fix: Direct-injection HPFP on S63TU fails from fuel quality issues or internal wear. Requires valve cover removal and intake work for access. 4-6 hours labor, sensitive to timing during installation.
Estimated cost: $2,000-3,500
Buy only with comprehensive pre-purchase inspection including bore-scope and oil analysis; budget $3-5k annually for deferred maintenance surprises, but the driving experience is unmatched if you accept the cost of admission.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.