The 1980 Buick Century is a solid mid-size A-body platform, but engine and transmission durability issues dominate the repair landscape—particularly if equipped with the notorious 350 diesel or paired with the TH200 transmission.
350 Diesel Engine Self-Destruction
Common · high severityTypical onset: 40,000-80,000 mi
Symptoms: white smoke from exhaust, loss of compression, coolant in oil, catastrophic head gasket failure, cracked cylinder heads
Fix: The Oldsmobile 350 diesel suffers from weak head bolts and undersized head gaskets, leading to head failures and block cracking. Most require complete engine replacement or conversion to gas V8. Expect 20-30 labor hours for swap.
Estimated cost: $3,500-6,500
TH200 Transmission Failure
Common · high severityTypical onset: 60,000-100,000 mi
Symptoms: slipping between gears, no 2nd gear, burnt transmission fluid smell, delayed engagement, complete loss of drive
Fix: The TH200 3-speed automatic is notorious for weak direct clutch packs and sun gear shell failures. Rebuilds rarely last—most shops recommend swapping to a TH350. Rebuild: 8-12 hours; swap to TH350: 10-14 hours including crossmember mods.
Estimated cost: $1,800-3,200
231 V6 Crankshaft Failure
Occasional · high severityTypical onset: 90,000-140,000 mi
Symptoms: heavy knocking from bottom end, metallic rattling at idle, loss of oil pressure, engine seized
Fix: The Buick 231 (3.8L) V6 has a weak rear main bearing area and #3 main journal that can spin bearings or crack the crank. Requires full teardown, crank regrind or replacement, and bearing set. 16-22 labor hours for short block rebuild.
Estimated cost: $2,200-3,800
Transmission Oil Cooler Line Leaks
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: red fluid pooling under car, transmission overheating, low fluid level, burnt fluid smell, slipping transmission
Fix: Steel cooler lines rust through at the radiator connections and at body mount contact points. Left unchecked, causes transmission starvation and failure. Replace all lines and rubber hoses as a set. 2-3 labor hours.
Estimated cost: $250-450
Transmission Mount Collapse
Common · medium severityTypical onset: 80,000-130,000 mi
Symptoms: heavy clunk when shifting into drive/reverse, excessive driveline vibration, visible engine movement when revving, transmission tail shaft sag
Fix: Rubber transmission mounts deteriorate and allow excessive drivetrain movement, accelerating U-joint and output shaft bushing wear. Replace transmission mount and inspect engine mounts simultaneously. 1.5-2.5 labor hours.
Estimated cost: $180-350
Carburetor Bowl Flooding (305/350 V8)
Occasional · low severitySymptoms: hard starting when hot, fuel smell in engine bay, flooding and black smoke, rough idle, stalling when warm
Fix: Rochester carburetors (E4ME, M4ME) have leaking needle/seat assemblies and warped float bowls that cause flooding. Rebuild kit and proper float adjustment typically resolves it. 3-4 labor hours for proper rebuild.
Estimated cost: $350-600
Fuel Filter Clogging (Diesel)
Common · medium severitySymptoms: hard starting, loss of power under load, engine stalling, rough running, long cranking time
Fix: Diesel engines require frequent fuel filter changes (every 5,000 mi) or water contamination causes filter plugging and injection pump damage. Always replace with AC Delco filter and drain water separator. 0.5-1 labor hour.
Estimated cost: $80-150
Buy a gas V8 or 231 V6 model with TH350 transmission and documented maintenance—avoid the diesel and TH200 at all costs unless priced for engine/trans replacement.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.