1972 BUICK CENTURION

Typical onset: 80,000-140,000 mi

Symptoms: Delayed engagement when shifting into drive or reverse, Slipping between 2nd and 3rd gear under load, Dark or burnt-smelling transmission fluid, Transmission running hot even in normal driving

Fix: The TH400 in these cars suffers from inadequate cooling, especially in stop-and-go driving. Transmission oil cooler lines corrode and restrict flow, or the radiator-mounted cooler clogs. Many units need full rebuilds by 120k miles. Rebuild takes 12-16 hours including removal/installation. Add auxiliary cooler during rebuild to prevent repeat failure.

Estimated cost: $2,200-3,800

Typical onset: 100,000-150,000 mi

Symptoms: Deep knocking from lower engine block, worse when cold, Low oil pressure at idle (under 10 psi) when warm, Metallic debris visible in oil filter, Vibration that increases with RPM

Fix: The 455 was detuned to 8.5:1 compression for 1972, but still uses soft bearing material from this emission-strangled era. Main bearings wear prematurely, and crankshaft journals score. Requires engine removal, crankshaft grinding (0.010" or 0.020" typically), and complete bottom-end rebuild. 24-32 hours labor for full rebuild including removal. Many owners opt for remanufactured long blocks instead.

Estimated cost: $4,500-7,200

Typical onset: 90,000-130,000 mi

Symptoms: Blue smoke on startup and acceleration, Oil consumption of 1 quart per 500-800 miles, Loss of compression, poor acceleration, Carbon buildup visible around exhaust ports

Fix: The low-compression 350 uses thin, flexible rings that wear quickly, especially if oil changes were skipped. Cylinder walls glaze over. Requires bore honing, new pistons and rings, valve job. Engine can stay in car if not doing main bearings. 18-24 hours labor for in-chassis ring and valve job.

Estimated cost: $2,800-4,200

Symptoms: Clunking when shifting from park to drive or reverse, Excessive driveline vibration at highway speeds, Visible sagging or cracks in rubber transmission mount, Transmission tailshaft housing sitting lower than normal

Fix: The rubber transmission mount degrades from heat and age, allowing excessive movement. This accelerates U-joint wear and stresses the transmission output shaft seal. Replacement requires supporting the transmission and unbolting the crossmember. 1.5-2.5 hours labor. Always inspect U-joints and output seal while the mount is off.

Estimated cost: $180-350

Symptoms: Hard starting after sitting overnight or longer, Engine stumbling or dying at idle after warmup, Hesitation during acceleration, Fuel smell near carburetor or fuel pump

Fix: Ethanol fuel deteriorates old rubber fuel lines and leaves varnish deposits throughout the system. Inline fuel filters clog quickly. Fuel pump diaphragms harden and fail. These cars need fuel filter replacement every 5,000 miles and often require carburetor rebuild and fuel line replacement. Filter change: 0.5 hours. Full fuel system refresh with new pump, filter, lines, and carb rebuild: 6-9 hours.

Estimated cost: $45-85 for filter only; $850-1,400 for complete fuel system overhaul

Typical onset: 60,000-100,000 mi

Symptoms: Power steering fluid puddles under front of car, Groaning noise when turning at low speeds, Steering effort increases gradually, Fluid level constantly low despite top-ups

Fix: Saginaw power steering components use seals that harden over decades. Gear box sector shaft seal and pump shaft seal are common leak points. Pump rebuild or replacement: 2-3 hours. Gear box reseal requires alignment afterward: 4-5 hours. Check high-pressure hose for cracks and swelling — often the actual culprit and much cheaper to replace.

Estimated cost: $320-650 for pump; $580-950 for gear box