1991 BMW M5

Typical onset: 80,000-120,000 mi

Symptoms: rattling noise on cold start that fades when warm, metallic clatter from front of engine, check engine light with cam/crank correlation codes, catastrophic engine failure if chain jumps

Fix: Complete timing chain service includes dual chains, tensioners, guides, and seals. This is a 12-16 hour job requiring front-end disassembly and special tools. Many shops recommend doing the water pump, thermostat, and accessory belts while in there. Neglect leads to jumped timing and bent valves.

Estimated cost: $3,500-5,500

Typical onset: 100,000-150,000 mi

Symptoms: metallic knocking at idle that worsens with RPM, low oil pressure readings, metal shavings in oil filter, sudden catastrophic engine failure

Fix: The S38's rod bearings wear prematurely, especially if oil changes were extended or wrong oil used. Inspection requires dropping the oil pan (8-10 hours). Replacement means full engine-out rebuild with new bearings, plastigauge clearance checks, and ARP studs recommended. Many owners go straight to full rebuild once bearings are suspect.

Estimated cost: $8,000-15,000

Typical onset: 60,000-100,000 mi

Symptoms: overheating in traffic or spirited driving, coolant weeping from hose connections, white residue around radiator neck, expansion tank cracking, sweet smell in cabin

Fix: Every rubber hose, the radiator, expansion tank, water pump, and thermostat become brittle after 25+ years. Piecemeal repairs lead to roadside failures. Smart move is complete system refresh: all hoses, radiator, water pump, thermostat, expansion tank, and fresh coolant. Figure 6-8 hours labor for comprehensive job.

Estimated cost: $1,800-3,000

Typical onset: 80,000-130,000 mi

Symptoms: whining or grinding noise that increases with vehicle speed, noise present in all gears including neutral while rolling, vibration through shifter, eventually leads to loss of drive

Fix: The Getrag 280 transmission's output shaft bearing is a known weak point. Requires transmission removal, disassembly, and replacement of the bearing and seal. While out, replace all seals, shift selector rod bushings, and check synchros. 10-14 hours labor.

Estimated cost: $2,200-3,500

Typical onset: 90,000-140,000 mi

Symptoms: hard starting when hot, rough idle and stumbling, fuel smell in cabin or garage, lean codes, fuel pressure loss after sitting

Fix: Fuel lines under the car corrode, in-tank pump fails, fuel filter clogs, and injector seals leak. The in-tank pump replacement requires dropping the tank (4-5 hours). Fuel line replacement along chassis adds another 6-8 hours. Injector cleaning and seal replacement is 3-4 hours. Address comprehensively or chase leaks for years.

Estimated cost: $1,500-3,500

Typical onset: 120,000+ mi

Symptoms: ticking or tapping from valve cover area, loss of power and rough running, poor compression on one or more cylinders, metal shavings in valve cover

Fix: High-mileage or abused S38 engines can experience cam lobe wear or cracked cylinder heads. Diagnosis requires valve cover removal and compression testing. Repair means head removal (both heads on I6), resurfacing, new cams, lifters, and valve job. 25-35 hours labor for complete job. Often triggers decision to do full engine rebuild instead.

Estimated cost: $6,000-12,000

Typical onset: 70,000-110,000 mi

Symptoms: clunking on acceleration or deceleration, vibration through chassis at highway speeds, wandering rear end feel, visible torn rubber on subframe mounts

Fix: Rear subframe bushings and differential mounts turn to mush. Replacement requires subframe drop or specialized tools to press bushings in place. Polyurethane upgrades available. 6-10 hours labor depending on method. Transforms the driving experience when worn.

Estimated cost: $1,200-2,000