1979 BMW 733I

Typical onset: 100,000-150,000 mi

Symptoms: Rattling on cold start that quiets after warmup, Oil weeping from valve cover and oil pan, Loss of power above 4,000 RPM, Metal shavings in oil filter during changes

Fix: Timing chain, tensioner, and guide rails need replacement around 120k mi or after long sitting periods. Budget 12-16 hours labor for proper chain service with new seals. Valve cover and oil pan gaskets add another 4-6 hours if done separately. Many survivors need full engine rebuilds due to worn rings and tired bearings.

Estimated cost: $2,800-5,500

Typical onset: 120,000-180,000 mi

Symptoms: Excessive oil consumption (1 qt per 500-800 miles), Blue smoke on deceleration, Low compression across multiple cylinders, Hard starting when hot

Fix: Early M30s had Nikasil-coated bores that suffer from sulfur in fuel. Requires bore inspection and either honing with new rings (8-12 hours) or complete rebuild with cylinder boring (25-35 hours). Many shops recommend going straight to full rebuild at this age given gasket and bearing condition.

Estimated cost: $4,500-8,500

Symptoms: Hard starting, especially when hot, Rough idle and stumbling under 2,500 RPM, Fuel smell in cabin or garage, Stalling when coming to stops

Fix: K-Jetronic mechanical injection is reliable but age-sensitive. Fuel distributor diaphragms harden, injector o-rings leak, and the warm-up regulator fails. Fuel accumulator often loses pressure. Plan on 6-10 hours for complete fuel system refresh including lines, filter, injectors, and regulator. Specialty knowledge required.

Estimated cost: $1,200-2,800

Typical onset: 80,000-120,000 mi

Symptoms: Clunk when shifting from Park to Drive, Vibration at highway speeds, Excessive driveline movement on acceleration, Transmission shifting harshly

Fix: Rubber transmission and differential mounts deteriorate badly after 40+ years. Transmission mount replacement is 3-4 hours, diff mount adds another 2-3 hours. Often find the subframe bushings also shot, adding complexity. Should be done as a set with driveshaft center bearing.

Estimated cost: $800-1,600

Symptoms: Overheating in traffic, Coolant leaks from multiple points, Heater not producing heat, Radiator tanks cracking at seams

Fix: At this age, assume the entire cooling system needs replacement: radiator, hoses, water pump, thermostat, expansion tank. Water pump alone is 4-5 hours due to tight access. Plan on replacing everything at once (8-12 hours total) rather than chasing individual leaks. Original brass radiators often have tank separation.

Estimated cost: $1,500-2,800

Symptoms: Intermittent gauge failures, Lights flickering or not working, Fuses blowing repeatedly, Random no-start conditions

Fix: Old German wiring insulation becomes brittle and cracks. Fusebox connections corrode, causing voltage drops and mysterious failures. Tracing wiring issues is time-intensive (often 4-8+ hours diagnostic). Main harness replacement requires 20-30 hours and specialty knowledge. Many owners live with quirks rather than full rewire.

Estimated cost: $600-3,500

Symptoms: Soft or spongy pedal, Brake fluid leaking at calipers or lines, Pulling to one side when braking, Parking brake ineffective

Fix: Brake lines rust from inside out, calipers seize, and master cylinder develops internal leaks. At 45 years, plan on complete brake system refresh: all hard lines, flex hoses, calipers, master cylinder, and booster inspection. Labor runs 10-14 hours for full system. Don't skip this on a purchase.

Estimated cost: $2,000-3,800