The E28 M5 is a legendary hand-built sedan with the S38 inline-six, known for stellar performance but demanding maintenance. Expect expensive engine work, fragile fuel systems, and wear items that cost more than regular 5-series parts.
S38 Engine Rebuild — Head Gasket and Valve Train Wear
Common · high severityTypical onset: 100,000-150,000 mi
Symptoms: oil consumption increasing beyond 1 qt per 1,000 mi, loss of compression, ticking or valve noise at cold start, white smoke from exhaust, coolant loss with no visible leaks
Fix: S38 engines wear valve guides, seals, and head gaskets. Full rebuild includes head removal, new gasket set, valve job, guides, seals, timing chain/tensioners. Expect 40-60 labor hours for a thorough rebuild with machine work. Many owners opt for full engine-out rebuild addressing bearings and rings simultaneously.
Estimated cost: $8,000-15,000
Crankshaft and Main Bearing Failure
Occasional · high severityTypical onset: 120,000-180,000 mi
Symptoms: deep knocking from lower engine, metallic rattle at idle that worsens under load, sudden oil pressure drop, metal shavings in oil filter
Fix: S38 main bearings can spin or wear severely if oil changes were neglected or oil starvation occurred. Requires engine removal, full teardown, crank inspection/machining, new bearings, often rings and rod bearings too. 50-70 labor hours total including R&R.
Estimated cost: $10,000-18,000
Fuel System Degradation — Injectors, Pump, and Lines
Common · medium severityTypical onset: 80,000-120,000 mi
Symptoms: hard starting when hot, stumbling or misfires under throttle, rough idle, fuel smell in cabin or engine bay, decreased fuel economy
Fix: Original Bosch injectors clog or leak, fuel pump weakens, rubber fuel lines crack. Injector cleaning or replacement (all six), new pump, and fuel line replacement recommended as a package. 8-12 labor hours depending on how many lines are replaced.
Estimated cost: $2,000-4,000
Transmission and Differential Mounts
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: clunk when shifting into gear or on throttle lift, excessive driveline vibration, shifter slop or misalignment, visible cracking or tearing in rubber mounts
Fix: Getrag 280 transmission mounts and diff mounts deteriorate. Replacing all mounts (trans, engine, diff) recommended as preventive package. 4-6 labor hours for all mounts.
Estimated cost: $800-1,500
Cooling System Overhaul — Radiator, Water Pump, Hoses
Common · high severityTypical onset: 70,000-110,000 mi
Symptoms: overheating in traffic or spirited driving, coolant leaks from hose connections, visible corrosion on radiator end tanks, steam from engine bay, heater performance loss
Fix: Original plastic radiator end tanks crack, water pump impellers corrode, and 30+ year-old hoses fail. Full cooling refresh includes radiator, pump, thermostat, all hoses, expansion tank. 6-10 labor hours.
Estimated cost: $1,500-2,800
Electrical Gremlins — Relay Board and Wiring Harness
Occasional · medium severitySymptoms: intermittent no-start, gauges cutting out randomly, check engine light with no codes stored, power windows or locks working sporadically, fuel pump cycling issues
Fix: E28 relay boards corrode and solder joints crack over time; engine bay wiring harnesses get brittle. Relay board repair/replacement and harness inspection/repair often needed. 4-8 labor hours depending on extent of damage.
Estimated cost: $600-1,800
Steering Box and Front Suspension Wear
Common · medium severityTypical onset: 80,000-130,000 mi
Symptoms: vague steering with play at center, clunking over bumps, wandering at highway speed, uneven tire wear on inside edges
Fix: Recirculating ball steering boxes develop slop, front control arm bushings and ball joints wear. Steering box rebuild or replacement plus full front-end bushings/joints. 8-12 labor hours.
Estimated cost: $1,800-3,500
Buy only if you have deep pockets and access to an S38-experienced mechanic — amazing driver's car, but maintenance costs rival exotic territory.
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.