1987 BMW L6

Typical onset: 100,000-180,000 mi

Symptoms: white smoke from exhaust, coolant loss with no visible leaks, overheating under load, milky oil on dipstick or cap

Fix: Head gasket job on the M30 requires pulling the head, machining if warped, new gaskets and timing components while you're in there. Budget 12-16 hours labor plus machine work. Do both heads if one fails—they're the same age.

Estimated cost: $2,500-4,000

Typical onset: 80,000-150,000 mi

Symptoms: overheating in traffic or highway, coolant leaks at hose connections, weeping from water pump weep hole, cracked plastic radiator end tanks

Fix: Original rubber hoses become brittle and fail catastrophically. Radiator end tanks crack. Water pump seals leak. Smart play is to replace entire system as preventive: radiator, all hoses, water pump, thermostat. 6-8 hours labor for comprehensive refresh.

Estimated cost: $1,200-2,200

Typical onset: 90,000-140,000 mi

Symptoms: transmission fluid leaking near radiator, burnt transmission fluid smell, slipping or delayed shifts when hot, pink fluid under car

Fix: The transmission cooler lines rust through or the cooler itself fails internally, sometimes cross-contaminating coolant and ATF. Replace lines and external cooler, flush transmission. 4-6 hours labor. Do not ignore—internal cooler failure can destroy the transmission.

Estimated cost: $800-1,400

Typical onset: 150,000-220,000 mi

Symptoms: low oil pressure at idle when hot, blue smoke on startup or deceleration, knocking or rumbling from bottom end, excessive oil consumption (1 qt per 500-1000 mi)

Fix: High-mileage M30s develop worn main bearings or piston ring blow-by. Full engine rebuild or long block replacement is the proper fix. 30-40 hours labor for out-and-back engine rebuild, including machine work and all seals/gaskets.

Estimated cost: $6,000-10,000

Typical onset: 80,000-130,000 mi

Symptoms: hard starting when hot, stumbling or hesitation under acceleration, smell of raw fuel in cabin or garage, no-start condition

Fix: In-tank fuel pump fails, fuel filter clogs (often neglected), and injector o-rings harden and leak. Replace fuel filter every 30k, pump as needed (2-3 hours), injector seals while doing any injector work (add 2 hours).

Estimated cost: $400-1,200

Typical onset: 70,000-120,000 mi

Symptoms: clunking when shifting or on/off throttle, excessive driveline vibration, vague or sloppy shifter feel (manual), transmission visible sagging

Fix: Rubber transmission and diff mounts deteriorate, causing clunking and vibration. Shifter bushings wear out on manuals. Replace mounts (2-3 hours) and bushings (1-2 hours). Low severity but annoying and accelerates other wear.

Estimated cost: $500-1,000

Symptoms: intermittent gauge failures, no-start with no crank, power windows or HVAC blower cutting out, dash lights flickering

Fix: Corroded fuse box connections and failing relays plague aging E24s. Main ground straps deteriorate. Diagnosis can be time-consuming (2-4 hours), fixes are usually cleaning connections, replacing relay board, and adding supplemental grounds.

Estimated cost: $300-900