1977 BUICK RIVIERA

Typical onset: 80,000-130,000 mi

Symptoms: heavy rod knock on cold start, metallic rattle under load, sudden loss of oil pressure, metal shavings in oil filter

Fix: The even-fire 231 had notoriously weak main and rod bearings that would spin under stress or oil starvation. Requires full short-block rebuild or replacement—engine pull, machine work, new bearings, rings, timing cover reseal. 18-24 labor hours typical for R&R and rebuild.

Estimated cost: $2,800-4,200

Typical onset: 60,000-120,000 mi

Symptoms: milky/pink transmission fluid, transmission slipping after radiator work, sudden no-forward gears, coolant loss with no visible leaks

Fix: The internal trans cooler in the radiator would corrode through, allowing coolant into ATF (destroys clutches instantly) or ATF into coolant. Requires radiator replacement, full transmission flush/rebuild, new cooler lines. If caught early (just lines), 3-4 hours. If trans is contaminated, add 12-16 hours for rebuild.

Estimated cost: $800-1,200 (lines/radiator only); $2,200-3,800 (with transmission rebuild)

Typical onset: 90,000-150,000 mi

Symptoms: deep rumbling knock that worsens with RPM, oil pressure drops at idle when hot, vibration through whole car, eventually seizes

Fix: Late-'70s small-block Chevys in these had softer castings and marginal oiling if oil changes were skipped. Requires crank removal, inspection, possible turning or replacement, all new bearings. Full teardown, 20-28 hours including removal and reinstall.

Estimated cost: $3,200-5,000

Symptoms: hard starting when warm, severe hesitation off idle, black smoke, stalling at stops, failed emissions test

Fix: Rochester Quadrajet carbs were reliable when maintained but became nightmares when vacuum hoses rotted and EGR valves coked up. Most surviving examples have band-aid repairs. Proper rebuild with all new vacuum lines, EGR service, choke adjustment takes 4-6 hours.

Estimated cost: $450-850

Typical onset: 70,000-110,000 mi

Symptoms: blue smoke on startup, quart of oil every 500-800 miles, oil fouling on spark plugs, rough idle when cold

Fix: Low-tension rings of the era wore quickly, especially if air filters weren't changed. Ring job requires head removal, honing, new rings, valve seals while you're in there. 14-18 hours labor.

Estimated cost: $1,800-2,800

Typical onset: 80,000+ mi

Symptoms: clunk when shifting into drive or reverse, vibration at idle in gear, visible sag of transmission tailshaft

Fix: Rubber mounts deteriorate from heat and age. Replacement is straightforward—jack trans slightly, unbolt old mount, install new. 1.5-2 hours.

Estimated cost: $180-320