1959 CADILLAC SEVILLE

Symptoms: Deep knocking sound from crankcase especially when cold, Oil pressure dropping below 10 psi at idle, Metallic debris in oil filter or pan, Sudden catastrophic failure if ignored

Fix: Given the age, most survivors have inadequate maintenance history and bearing wear from decades of sitting or marginal oil changes. Requires engine removal, full teardown, crankshaft inspection/machining, new main and rod bearings, plus new gaskets throughout. Budget 30-40 labor hours for proper rebuild including machine shop time.

Estimated cost: $6,500-12,000

Symptoms: Excessive vibration through floorboards at idle in gear, Clunking when shifting from Park to Drive, Visible sag of transmission tailshaft, Driveline vibration at highway speed

Fix: Original rubber mounts are 65 years old and deteriorate even in garage-kept cars. Requires lifting vehicle, supporting transmission with jack, removing crossmember. Replacement mounts are available from specialized Cadillac vendors. 2-3 hours labor if access is clear.

Estimated cost: $350-650

Symptoms: White smoke from exhaust on cold start, Coolant loss with no visible external leaks, Oil contamination in coolant reservoir (milky residue), Overheating under load, Rough idle or misfiring on one bank

Fix: The 390 runs high compression (10.5:1) and vintage gaskets fail from age and thermal cycling. Both heads should be removed, checked for warpage, and decked if needed. Exhaust manifold studs often break requiring extraction. 18-24 hours labor plus machine work.

Estimated cost: $3,500-6,000

Symptoms: Transmission fluid puddles under front of vehicle, Fluid spraying onto exhaust manifolds (visible smoke), Rapid loss of transmission fluid, Slipping or failure to engage gears after fluid loss

Fix: Original steel lines rust through or crack at flare fittings due to age and vibration. Lines run along frame rail to radiator-mounted cooler. Replacement requires custom fabrication or NOS parts. Flush cooling system if coolant contaminated. 3-5 hours depending on condition.

Estimated cost: $450-850

Typical onset: 80,000-150,000 mi

Symptoms: Excessive blue smoke on deceleration or startup, Oil consumption above 1 quart per 500 miles, Loss of compression across multiple cylinders, Poor acceleration and power loss, Positive crankcase pressure (oil filler cap blows off)

Fix: Rings wear or stick from old oil chemistry and extended sitting periods. Proper fix requires bore inspection, honing or reboring, new pistons and rings. If cylinders are glazed but not worn, re-ring job is possible. 25-35 hours for complete overhaul.

Estimated cost: $4,500-8,500

Symptoms: Hard starting especially when cold, Stumbling or hesitation during acceleration, Flooding with raw fuel smell, Stalling at idle or when coming to stops, Fuel leaking from carburetor base gaskets

Fix: Rochester 4-barrel carburetors gum up from ethanol fuel and sitting. Requires complete disassembly, ultrasonic cleaning, new gaskets and accelerator pump. Replace fuel filter and blow out lines. Most shops send carbs out to specialists. 4-6 hours plus rebuild wait time.

Estimated cost: $650-1,200