1971 CADILLAC FLEETWOOD

Typical onset: 80,000-140,000 mi

Symptoms: Slipping between gears, especially 1st to 2nd, Delayed engagement when shifting to Drive or Reverse, Transmission fluid dark brown or burnt-smelling, Clunking or harsh shifts under acceleration

Fix: The TH400 in these cars takes a beating from the 472's torque and decades of heat cycling. Full rebuild typically takes 12-16 hours including R&R. Expect to replace clutch packs, bands, seals, modulator valve, and often the torque converter. Transmission cooler lines frequently leak at the radiator connections and should be addressed simultaneously.

Estimated cost: $2,200-3,800

Typical onset: 100,000-150,000 mi

Symptoms: Blue smoke on startup that clears after warmup, Consuming 1+ quart per 500-800 miles, Loss of power under load, Fouled spark plugs on cylinders 2, 4, 6, 8 (common pattern)

Fix: The 472's piston rings wear unevenly, often worse on the passenger-side bank due to heat distribution. Proper fix requires engine-out rebuild with piston ring replacement, cylinder honing, and valve work. Budget 35-45 hours labor for complete job. Many owners band-aid this with heavier oil (20W-50) but that's temporary. If main bearings show wear, expect full rebuild rather than ring-only job.

Estimated cost: $4,500-7,500

Symptoms: Hard starting when hot, Raw fuel smell in garage after parking, Stumble or flat spot during acceleration, Black smoke under heavy throttle, Fuel leaking from carburetor base

Fix: The Rochester 4-barrel carbs on these cars suffer from deteriorated floats, worn throttle shafts, and bad accelerator pump diaphragms after 50 years. Rebuilds run 4-6 hours including proper adjustment and tuning. Many shops just throw parts at it—you need someone who understands Q-jets specifically. Alternative is a reman unit ($450-650 core exchange) which saves diagnostic time.

Estimated cost: $600-1,200

Symptoms: Temperature gauge climbing past 220°F in traffic or hills, Steam from hood after shutdown, Coolant pushing out overflow tube, Heater performance degraded

Fix: These 5,000-lb cars with 375hp V8s were marginal on cooling from the factory. Original 2-row radiators are typically collapsed internally. Proper fix is re-core with 3-row or aluminum replacement, new 180° thermostat, water pump, all hoses, and flush the block. The viscous fan clutch often fails—test by trying to spin fan with engine off (should have resistance). Complete cooling overhaul runs 8-12 hours.

Estimated cost: $1,400-2,200

Symptoms: Engine dies at idle after warmup, Surging at steady cruise, Hard restart after sitting 30+ minutes, Fuel smell but visible leaks not obvious

Fix: Modern ethanol fuel destroys original rubber fuel lines, causes sending unit failures, and leaves varnish throughout. Mechanical fuel pump diaphragms harden and leak internally. Proper fix includes new fuel pump, replacement of all rubber fuel lines from tank to carb (6-8 hours), in-line filter, and tank cleaning if contaminated. The steel lines rust from inside-out in humid climates—inspect carefully.

Estimated cost: $800-1,500

Typical onset: 60,000-100,000 mi

Symptoms: Clunk when shifting from Park to Drive, Excessive vibration at idle in gear, Visible engine movement when revving in Park, Transmission clunk over bumps

Fix: The rubber mounts last 15-20 years maximum before they're mush. Engine mount replacement requires supporting the engine safely—4 hours labor for both sides. Transmission mount is 2 hours. Failed mounts accelerate wear on exhaust pipes, shift linkage, and the transmission itself. These are heavy drivetrains that need solid mounting.

Estimated cost: $500-800