The F90 M5's S63 twin-turbo V8 is a performance powerhouse but carries serious rod bearing and cooling system risks that can lead to catastrophic engine failure if ignored. This generation is still relatively new, so high-mileage horror stories are just starting to emerge, but patterns from the F10 generation suggest expensive issues ahead.
Rod Bearing Failure (S63TU4 Engine)
Occasional · high severityTypical onset: 60,000-100,000 mi
Symptoms: metallic knocking at idle or under load, metal shavings in oil during analysis, sudden oil pressure drop, catastrophic engine seizure if ignored
Fix: Preventive bearing replacement requires engine-out, full disassembly, and precision clearance work—about 25-30 hours labor. If the crank is scored, add machine work or crankshaft replacement. Catastrophic failure means short block or complete rebuild.
Estimated cost: $8,000-15,000 preventive; $25,000-40,000 after failure
Transmission Oil Cooler Line Leaks
Common · medium severityTypical onset: 40,000-80,000 mi
Symptoms: transmission fluid seepage around cooler lines, burnt fluid smell, transmission overheating warning, fluid spots under car near transmission tunnel
Fix: Replace cooler lines and seals, sometimes requires subframe drop for access—8-12 hours labor depending on line location. Flush transmission fluid and verify no internal damage from overheating.
Estimated cost: $1,800-3,200
Transmission Mount Failure (ZF 8HP)
Common · low severityTypical onset: 50,000-90,000 mi
Symptoms: clunk on aggressive shifts or hard acceleration, vibration through center console at idle, drivetrain slop during throttle tip-in, visible cracking or tearing in rubber mount
Fix: Replace transmission mount and inspect neighboring engine mounts while underneath—3-5 hours labor. Aggressive driving and launch control abuse accelerate wear.
Estimated cost: $800-1,400
High-Pressure Fuel Pump Failure
Occasional · high severityTypical onset: 30,000-70,000 mi
Symptoms: long crank before starting, rough idle and misfires under load, limp mode with fuel system fault codes, metal contamination in fuel system if pump grenades
Fix: Replace high-pressure fuel pump, filter, and inspect injectors for debris—6-9 hours labor. If pump fails catastrophically, injectors and fuel rails may need replacement due to metal contamination.
Estimated cost: $2,500-4,500; up to $8,000 with injector replacement
Turbocharger Wastegate Rattle
Occasional · medium severityTypical onset: 50,000-100,000 mi
Symptoms: rattling noise on cold start that fades when warm, loss of boost pressure, turbo underboost codes, exhaust smoke under hard acceleration
Fix: Replace affected turbocharger(s)—wastegate bushings wear and cannot be serviced separately. Each turbo requires 8-12 hours labor due to tight engine bay packaging. Both turbos often replaced together.
Estimated cost: $4,000-6,500 per turbo; $8,000-12,000 for both
Coolant System Leaks (Turbo Coolant Lines)
Occasional · medium severityTypical onset: 40,000-80,000 mi
Symptoms: coolant smell from engine bay, low coolant warning, visible seepage near turbos or valley, overheating under sustained load
Fix: Replace turbo coolant feed and return lines, often requires partial engine disassembly for access—10-14 hours labor. Pressure-test entire system and replace expansion tank if brittle.
Estimated cost: $2,200-3,800
Buy only with comprehensive records, recent oil analysis showing clean bearings, and a serious maintenance fund—this is a $20k+ grenade if the engine lets go.
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.