1978 BUICK SKYHAWK

Typical onset: 80,000-140,000 mi

Symptoms: Blue smoke on startup and acceleration, Rapid oil loss between changes (quart every 500-800 miles), Rod knock or main bearing rumble, Low oil pressure at idle when warm

Fix: The 231 V6 eats piston rings and valve seals, leading to oil starvation and spun bearings. Full engine rebuild (pistons, rings, bearings, machine work) runs 20-30 hours labor. Many shops recommend a junkyard long block swap instead due to age—expect 12-16 hours for R&R.

Estimated cost: $2,800-5,500

Typical onset: 70,000-120,000 mi

Symptoms: Transmission fluid leaking at radiator connections, Pink frothy fluid in coolant reservoir (internal cooler failure), Erratic shifting or slipping after coolant contamination, Overheating transmission in hot weather or towing

Fix: Steel cooler lines rust through at brackets or the radiator fails internally, mixing ATF and coolant. External line replacement is 1.5-2 hours. Internal radiator cooler failure requires radiator replacement plus full trans flush—total 4-6 hours. If coolant entered trans, expect rebuild.

Estimated cost: $250-450 (lines only), $1,800-3,200 (with trans damage)

Typical onset: 90,000-130,000 mi

Symptoms: Deep knocking from bottom end that worsens under load, Metal shavings in oil filter or pan, Oil pressure drops below 10 psi at hot idle, Vibration through entire drivetrain

Fix: The even-fire 231 had marginal main bearing design and poor oiling under sustained load. Once bearings go, crank usually needs grinding or replacement. Full teardown, machine work, bearings, seals—figure 25-35 hours including R&R. Short block swap is 14-18 hours but cores are scarce.

Estimated cost: $3,200-6,000

Typical onset: 60,000-100,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive vibration at idle in gear, Visible tail shaft sagging when viewed from side, Hard shift engagement

Fix: Rubber transmission mount deteriorates and the stamped crossmember cracks at weld points. Mount replacement alone is 1-1.5 hours, but crossmember work adds 2-3 hours for welding or fabrication if cracks are present. Inspect carefully before buying.

Estimated cost: $180-320 (mount only), $400-650 (with crossmember repair)

Symptoms: Strong fuel smell inside cabin or underhood, Visible wet spots on steel fuel lines along frame rail, Hard starting after sitting due to vapor lock, Fuel dripping onto hot exhaust components

Fix: Steel fuel lines rust from inside out, especially in salt states. From tank to carb is a full replacement job—4-6 hours to fabricate or run premade lines. This is a fire hazard; address immediately. Add inline fuel filter replacement (30 min) at same time.

Estimated cost: $350-700

Typical onset: 90,000-140,000 mi

Symptoms: Slipping on 1-2 or 2-3 upshift under moderate throttle, Delayed engagement into Drive (2-3 seconds), No engine braking in L or 2 ranges, Burnt ATF smell or dark brown fluid

Fix: The TH200 was GM's weakest automatic—barely adequate for the V6, hopeless with the 305. Clutches wear and valve body bores get sloppy. Full rebuild with updated clutches and shift kit runs 8-12 hours. Swap to TH350 if doing the work—marginally more expensive but far more durable.

Estimated cost: $1,400-2,200 (TH200 rebuild), $1,800-2,600 (TH350 swap)