1977 BUICK SKYHAWK

Typical onset: 80,000-120,000 mi

Symptoms: Heavy knocking from bottom end especially when cold, Metal shavings in oil filter during changes, Sudden catastrophic oil pressure loss, Severe vibration that worsens with RPM

Fix: This is the Buick 231's Achilles heel—cast crank and undersized mains can't handle sustained RPM or deferred oil changes. Requires full engine teardown, crank grinding (if salvageable) or replacement, new bearings, align boring if journals are out of spec. 18-24 hours labor for proper rebuild with machine work.

Estimated cost: $2,800-4,200

Typical onset: 90,000-130,000 mi

Symptoms: Blue smoke on startup that clears after warmup, Excessive oil consumption (quart every 500-800 miles), Reduced compression on cylinder leak-down test, Fouled spark plugs on cylinders 2, 4, or 6

Fix: The 231's soft cylinder walls and inadequate ring package leads to blow-by. Requires bore measurement—if under .010 over, hone and new rings (12-15 hours). Beyond that, needs bore and oversized pistons or sleeving (20-26 hours with machine shop time).

Estimated cost: $1,800-3,500

Typical onset: 70,000-110,000 mi

Symptoms: Transmission fluid weeping from radiator cooler connections, Delayed engagement into drive or reverse (3+ seconds), Slipping between 1-2 shift under load, Milky pink fluid indicating coolant contamination

Fix: The small TH200 (base transmission) is marginal for even the V6's torque—cooler line corrosion or radiator failure mixes coolant into ATF, destroying clutches and bands. Requires transmission rebuild with updated frictions and bands, plus external cooler installation. 14-18 hours with R&R.

Estimated cost: $1,900-2,800

Typical onset: 60,000-100,000 mi

Symptoms: Clunk when shifting from park to drive or reverse, Excessive driveline vibration at idle in gear, Visible transmission tail shaft sag when inspected on lift, Shifter linkage feels loose or imprecise

Fix: The rubber mount deteriorates from heat and oil exposure—common on all H-bodies. Replacement is straightforward but requires supporting transmission with jack while removing crossmember. 1.5-2.5 hours labor.

Estimated cost: $180-320

Symptoms: Hard starting when hot (heat soak), Fuel smell in cabin or garage after shutdown, Idle surging between 500-1200 RPM, Black smoke and poor fuel economy (under 12 mpg city)

Fix: These Rochester carbs suffer from ethanol fuel degrading gaskets and needle-seat assemblies. Sitting cars develop varnish in passages. Needs full carburetor rebuild with ethanol-compatible kit, fuel filter replacement, and often fuel line inspection for deterioration. 3-4 hours for proper rebuild and tuning.

Estimated cost: $380-650

Typical onset: 80,000-140,000 mi

Symptoms: Coolant seepage at intake manifold valley, Overheating in stop-and-go traffic, White residue or crusty buildup at front/rear manifold corners, Rough idle and occasional misfire when cold

Fix: The 305's composite intake gaskets fail from heat cycling—coolant leaks internally or externally. Requires intake removal, deck surface cleaning, and quality replacement gaskets (use Fel-Pro). 5-7 hours labor including coolant flush.

Estimated cost: $520-880