1988 BMW M6

Typical onset: 80,000-150,000 mi

Symptoms: metallic knocking or ticking at idle that worsens under load, low oil pressure warnings, metal shavings in oil during changes, sudden catastrophic failure if ignored

Fix: S38 engines are notorious for rod and main bearing wear, especially if oil changes were neglected or extended. Prevention means 3,000-5,000 mi oil changes with quality oil. Once bearings knock, it's engine-out for bearing replacement (12-16 hours labor) or full rebuild (25-35 hours). Many owners opt for preventive bearing replacement at 100k mi. Crankshaft polishing or replacement often needed if caught late.

Estimated cost: $8,000-15,000

Typical onset: 60,000-100,000 mi

Symptoms: overheating in traffic or spirited driving, coolant leaks from aged hoses or radiator end tanks, fluctuating temperature gauge, coolant smell in cabin or visible steam

Fix: Original plastic and rubber components are 35+ years old and fail without warning. Radiator end tanks crack, water pump impellers corrode, hoses burst. Smart owners replace the entire system as preventive maintenance: radiator, water pump, all hoses, thermostat, expansion tank. Labor 6-8 hours for complete overhaul. Overheating can warp the head or crack the block on the S38.

Estimated cost: $2,000-3,500

Typical onset: 70,000-120,000 mi

Symptoms: hard starting when hot, rough idle or misfires, hesitation under acceleration, fuel smell or visible leaks under the car, check engine light with lean/rich codes

Fix: Bosch Motronic injection system is reliable but old rubber fuel lines crack and leak, in-tank pump weakens, injectors clog or leak. Fuel filter should be changed every 15k-20k mi but is often neglected. Full fuel system refresh (pump, filter, all rubber lines, injector cleaning or replacement) takes 8-12 hours. Leaking fuel is a fire hazard—address immediately.

Estimated cost: $1,800-4,000

Typical onset: 50,000-100,000 mi

Symptoms: clunking when shifting or engaging clutch, excessive drivetrain movement, gear oil leaks at tailshaft or shifter base, difficult or notchy shifts when cold

Fix: Transmission mounts collapse with age, causing harsh engagement and driveline vibration. The Getrag 280 is mechanically stout but seals dry out and leak. Mount replacement is 2-3 hours. Transmission reseal with new tailshaft seal, shift selector seals, and fluid change adds another 4-6 hours if done properly. Oil cooler lines can also leak or corrode through.

Estimated cost: $800-2,000

Symptoms: intermittent no-start conditions, gauges that stop working randomly, check engine light with no stored codes, accessories that cut in and out, fuel pump not priming

Fix: The Motronic 1.1 DME and associated relay boards suffer from cold solder joints and corroded connectors after decades. Common failures: main relay, fuel pump relay, instrument cluster voltage stabilizer. Diagnosis can be time-consuming (2-4 hours). Relay board refurbishment or replacement, DME repair, and connector cleaning typically resolve issues. Some owners upgrade to modern relays.

Estimated cost: $500-1,500

Typical onset: 120,000-180,000 mi

Symptoms: rattling or whirring noise from front of engine at startup, noise that disappears after a few seconds as oil pressure builds, check engine light or poor running if chain has jumped

Fix: S38 uses a single-row chain with plastic guides that wear over time. If the chain rattles on cold start, guides are failing. Jumped timing can bend valves. Replacement requires engine-out or significant disassembly (18-24 hours labor). Should be inspected during any major engine work and replaced if questionable. Not as common as BMW M20/M30 issues but still a concern on high-mileage examples.

Estimated cost: $4,000-6,500