1976 CADILLAC SEVILLE

Typical onset: 80,000-120,000 mi

Symptoms: Knocking or rod knock at idle, especially when warm, Sudden metallic clattering under load, Rapid oil pressure drop, Metal shavings in oil filter during changes

Fix: The Olds 350 used in these Sevilles has notoriously weak connecting rod bearings and marginal oiling to the mains. Full engine rebuild is typical — expect 18-24 labor hours for R&R plus internal work. Many shops recommend going straight to a rebuilt long block rather than risking machine work on a cracked block.

Estimated cost: $3,500-6,500

Typical onset: 60,000-100,000 mi

Symptoms: Transmission fluid in radiator or coolant in transmission, Pink milkshake appearance in radiator overflow, Erratic shifting or slipping after brief highway run, Transmission overheating gauge warning

Fix: The factory cooler inside the radiator deteriorates and cross-contaminates coolant with ATF, which destroys the transmission. Requires radiator replacement or external cooler retrofit, plus full transmission flush or rebuild if contamination occurred. 6-8 hours labor for radiator and external cooler install; add 12-16 hours if transmission rebuild needed due to coolant damage.

Estimated cost: $800-1,200 (cooler only), $2,200-3,800 (if trans damaged)

Typical onset: 70,000-110,000 mi

Symptoms: Severe clunk when shifting from Park to Drive or Reverse, Driveline vibration at highway speed, Visible engine/trans sag when viewed from side, Exhaust system contact or rattles

Fix: The rubber transmission mount deteriorates and allows excessive drivetrain movement. Common on these due to weight and torque of the 350. Replacement is straightforward but requires supporting the transmission. 2-3 hours labor.

Estimated cost: $250-450

Symptoms: Hard starting when hot, especially after short trips, Hesitation or stumble on acceleration, Black smoke from tailpipe under load, Fuel smell in cabin or engine bay, Stalling at idle after warmup

Fix: The Rochester 4-barrel carb and fuel pump are age-sensitive. Ethanol fuel deteriorates accelerator pump diaphragms and causes varnish buildup. Mechanical fuel pump failures common. Carb rebuild runs 3-4 hours; fuel pump replacement 1-2 hours. Many owners add inline fuel filter to prevent carb contamination.

Estimated cost: $400-800 (carb rebuild), $150-300 (fuel pump)

Typical onset: 100,000-150,000 mi

Symptoms: Deep knocking that varies with RPM, Oil pressure fluctuation or steady decline, Visible crankshaft end play movement, Metal particles in oil pan

Fix: When the bottom end goes, it's often the mains, not just rod bearings. Crankshaft R&R requires full disassembly and usually machining or replacement. At this point, most shops recommend complete short block replacement rather than piece-by-piece repair. 20-28 hours total labor.

Estimated cost: $4,000-7,000

Typical onset: 80,000-120,000 mi

Symptoms: Coolant seepage at front or rear of intake manifold, Rough idle or misfire when cold, Sweet coolant smell from engine bay, Overheating in traffic or slow climbs

Fix: Intake gaskets dry out and leak coolant into valley or externally. Combined with weak water pump and clogged radiator cores on survivors, cooling becomes marginal. Intake gasket job is 4-6 hours; budget for radiator and water pump while it's apart.

Estimated cost: $600-1,200