The 1987 Buick Century is a practical A-body GM that suffers primarily from transmission durability issues and engine wear related to the 2.5L Iron Duke and early 2.8L V6 powertrains. The 3.8L V6 is notably more reliable but wasn't as common in this model year.
TH125C/3T40 Automatic Transmission Failure
Common · high severityTypical onset: 80,000-130,000 mi
Symptoms: slipping between gears, especially 2nd to 3rd, delayed engagement when shifting to Drive, whining or grinding noise during acceleration, transmission fluid dark or burnt smelling
Fix: The 3-speed automatic is the Achilles heel of these cars. Internal clutch packs and governor wear lead to slippage. Rebuild runs 12-16 hours labor, or 8-10 hours for a used/reman swap. Filter and fluid service every 30k can延 life but won't prevent eventual failure.
Estimated cost: $1,400-2,200
2.5L Iron Duke (151ci I4) Piston Ring and Cylinder Wear
Common · medium severityTypical onset: 110,000-160,000 mi
Symptoms: blue smoke on startup and acceleration, excessive oil consumption (1 qt per 500-800 miles), loss of power and rough idle, poor compression test results
Fix: The Iron Duke burns oil as rings wear and cylinder walls glaze over. A proper fix requires boring cylinders 0.020-0.030 over, new pistons, rings, and typically rod and main bearings while it's apart. Engine-out rebuild is 18-24 hours; some opt for a junkyard 2.8L V6 swap instead.
Estimated cost: $2,200-3,500
2.8L V6 (173ci) Intake Manifold Gasket Failure
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: coolant leaking externally at intake edges, white exhaust smoke after cold starts, coolant loss with no visible external puddles, rough idle and misfires from coolant entering cylinders
Fix: The lower intake gasket deteriorates and allows coolant into the crankcase or cylinders. Repair requires upper and lower intake removal, new gaskets, and often new coolant elbows. Book time is 4-6 hours. Check oil for milky appearance before buying.
Estimated cost: $450-750
Crankshaft Main Bearing Wear (2.5L I4)
Occasional · high severityTypical onset: 130,000-180,000 mi
Symptoms: deep knocking sound from lower engine at idle, oil pressure dropping below 10 psi at hot idle, metallic rattling that increases with RPM, metal shavings visible in oil filter or pan
Fix: The Iron Duke's main bearings wear from inadequate oiling or extended oil change intervals. Once knocking starts, it's a full teardown: crank polishing or replacement, line boring if needed, all bearings. 20-26 hours labor. Most opt for a used engine swap at this point.
Estimated cost: $2,800-4,200
Engine and Transmission Mount Deterioration
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: clunking when shifting into gear, excessive engine movement visible when revving in Park, vibration at idle that smooths out at speed, shifter feels loose or sloppy
Fix: Rubber mounts crack and separate, especially the front torque strut and transmission mount. These are straightforward replacements—1.5-2.5 hours total for both engine and trans mounts. Do them together as a set.
Estimated cost: $200-380
Fuel System Varnish and Filter Clogging
Occasional · medium severitySymptoms: hard starting after sitting overnight, sputtering or hesitation under acceleration, stalling at idle after warmup, fuel pressure below spec (9-13 psi TBI system)
Fix: Old gasoline varnish clogs the in-tank sock filter and inline filter on TBI models. Filter replacement is 0.5 hours, but if the tank is contaminated, drop and clean adds 3-4 hours. Fuel pump replacement while tank is down is common insurance (add $150-250 parts).
Estimated cost: $180-550
Decent $1,500 beater if the transmission shifts cleanly and doesn't burn oil; anything needing a rebuild costs more than the car is worth.
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.