1967 CADILLAC DEVILLE

Symptoms: Transmission fluid mixing with coolant (strawberry milkshake in radiator), Sudden transmission slipping or failure to engage gears, Overheating transmission after cooler lines rust through

Fix: Factory oil cooler inside the radiator corrodes after decades, contaminating both fluids. Requires radiator removal, rebuilding or replacing cooler, flushing entire cooling and transmission systems, often necessitating transmission rebuild if contamination went unnoticed. 8-12 hours labor if trans needs rebuild, 4-6 hours if caught early.

Estimated cost: $1,200-3,500

Typical onset: 100,000-150,000 mi

Symptoms: Deep knocking sound from crankcase at idle, worse under load, Sudden drop in oil pressure, Metallic debris in oil pan or filter, Catastrophic loss of compression in one or more cylinders

Fix: High-mileage 429s develop rod bearing wear from decades of use and inconsistent oil changes. Full teardown required: remove engine, disassemble short block, machine crank if needed, replace all bearings, pistons/rings if scored. Expect 20-30 hours labor for complete engine rebuild with machine work.

Estimated cost: $3,500-6,500

Symptoms: Loud clunk when shifting from Park to Drive or Reverse, Excessive drivetrain movement visible under acceleration, Vibration through floorboard at highway speeds, Transmission tail housing sitting visibly low

Fix: Original rubber mounts collapse after 50+ years, allowing transmission to sag and stress the driveshaft. Replacing mount and inspecting crossmember for rust-through is essential. 2-3 hours labor, straightforward job but requires transmission support.

Estimated cost: $250-500

Typical onset: 80,000-120,000 mi

Symptoms: Blue smoke on startup or deceleration (worn valve seals), Cylinder misfires or rough idle from burned/recessed valves, Excessive valve train noise (ticking/tapping) despite adjustment, Loss of compression on specific cylinders

Fix: Valve seats recede into soft cast iron heads over time, valves burn from leaded-fuel-era wear patterns. Complete valve job requires heads off, machining seats, new valves/guides/seals, resurfacing. Can be done in-chassis. 12-16 hours labor plus machine shop time.

Estimated cost: $2,000-3,500

Symptoms: Engine stalling when hot, especially after short trips (vapor lock), Hard starting after sitting, fuel smell near tank, Erratic idle or hesitation from varnished carburetor, Fuel leaks at tank, lines, or pump connections

Fix: Original rubber fuel lines, tank sending unit seals, and mechanical fuel pump diaphragms fail after decades. Ethanol fuel accelerates degradation. Replace all rubber fuel lines, filter, pump, rebuild Rochester carburetor. Vapor lock fixed by insulating fuel lines from exhaust heat. 6-8 hours labor for comprehensive fuel system refresh.

Estimated cost: $800-1,500

Typical onset: 120,000+ mi

Symptoms: Heavy blue smoke under acceleration, Excessive oil consumption (quart every 500-800 miles), Cylinder glazing visible during compression test, Loss of power and poor fuel economy

Fix: Original rings wear from decades of heat cycles; cylinder walls glaze over. Requires pulling engine, honing or boring cylinders, new pistons/rings, ridge reaming. Often combined with bearing replacement during rebuild. 18-25 hours labor for complete overhaul.

Estimated cost: $3,000-5,500