1980 CADILLAC FLEETWOOD

Typical onset: 60,000-100,000 mi

Symptoms: white smoke from exhaust, coolant loss with no external leaks, hard starting when warm, milky oil on dipstick, loss of compression

Fix: The Oldsmobile 350 diesel has inadequate head bolts that allow head gasket failure, leading to cracked blocks and destroyed main bearings. Fix requires complete engine replacement or rebuild with ARP studs conversion. Expect 25-35 labor hours for long block swap, 40-50 hours for in-car rebuild with machine work.

Estimated cost: $4,500-8,000

Typical onset: 80,000-120,000 mi

Symptoms: transmission fluid puddles under front of car, pink fluid mixing with coolant in radiator, transmission overheating, erratic shifting when hot

Fix: Steel cooler lines rust through at floorpan clips, or internal radiator cooler fails allowing ATF/coolant cross-contamination. External lines are 2-3 hours with custom bending or pre-fab replacements. Internal cooler failure requires radiator replacement or external auxiliary cooler addition (4-6 hours), plus complete fluid flush.

Estimated cost: $400-1,200

Typical onset: any mileage due to age

Symptoms: hard starting, fuel starvation at highway speeds, black smoke under acceleration, rough idle, fuel in oil from leaking injectors

Fix: Injection pump fails from modern low-sulfur diesel fuel destroying internal components designed for 1980s fuel. Rubber fuel lines deteriorate internally, creating debris. Complete system overhaul needs pump rebuild/replacement (8-12 hours), injector service, and all rubber line replacement. Fuel filter clogs rapidly if system contaminated.

Estimated cost: $2,500-4,500

Typical onset: 100,000+ mi

Symptoms: poor fuel economy worsening over time, rough idle, hesitation on acceleration, check engine light, flooding when hot

Fix: The Digital Fuel Injection system has failing pressure regulator, clogged injectors in throttle body, and deteriorating vacuum lines. TPS and coolant temp sensors also fail frequently. Diagnosis is 1-2 hours, throttle body rebuild with injector replacement runs 3-4 hours. Many shops convert to Quadrajet carburetor (6-8 hours) for reliability.

Estimated cost: $800-1,800

Symptoms: intermittent gauge failures, power accessories working randomly, twilight sentinel malfunction, cruise control dropout, climate control erratic operation

Fix: Early computer modules fail from capacitor degradation and corrosion. Engine bay harnesses get brittle from heat cycles. Individual circuits can be traced and repaired (2-4 hours per system), but complete harness replacement on diesel models particularly problematic due to glow plug controller integration (12-16 hours).

Estimated cost: $500-2,000

Typical onset: 80,000-150,000 mi

Symptoms: oil puddle centered under bellhousing, oil coating on transmission case, oil drips after shutdown, low oil level warnings

Fix: Two-piece rear main seal design eventually leaks on all examples. Requires transmission removal for access. Plan 8-10 hours labor on gas engine, 10-12 hours on diesel due to heavier components and tighter clearances. Often done during clutch or transmission work to save duplicate labor.

Estimated cost: $800-1,400