1987 CADILLAC SEVILLE

Typical onset: 50,000-90,000 mi

Symptoms: White smoke from exhaust indicating coolant burning, Overheating despite new thermostat and radiator, External coolant leaks from head gasket area, Oil contaminated with coolant (milky appearance), Loss of coolant with no visible external leaks

Fix: The aluminum block with cast-iron heads creates thermal expansion mismatches causing head gasket failure and often block cracking. Head gasket replacement requires 12-16 hours labor but often reveals cracked block requiring full engine replacement. Most shops recommend used engine swap or engine rebuild with upgraded bolts and block reinforcement. Engine R&R adds 18-24 hours total.

Estimated cost: $3,500-7,500

Typical onset: 60,000-100,000 mi

Symptoms: Heavy knocking noise from bottom end, especially on cold starts, Low oil pressure readings even after oil change, Metal shavings in oil filter, Sudden catastrophic engine seizure

Fix: Undersized oil passages and weak crankshaft design lead to bearing failure. Requires complete engine disassembly, crankshaft grinding or replacement, and all new bearings. Most cost-effective solution is used engine swap rather than rebuild. Short block replacement takes 20-26 hours including removal and reinstallation.

Estimated cost: $4,000-8,000

Typical onset: 70,000-120,000 mi

Symptoms: Blue smoke on startup and acceleration, Excessive oil consumption (1 quart per 500-800 miles), Fouled spark plugs, Failed emissions testing, Poor compression readings across multiple cylinders

Fix: Soft aluminum block and inadequate piston ring tension cause premature cylinder wear. Requires bore inspection, likely overbore with oversized pistons, new rings on all cylinders. Full rebuild with machine work takes 24-30 hours. Given engine's poor reputation, most techs recommend finding a low-mileage used engine instead.

Estimated cost: $3,800-6,500

Typical onset: 80,000-140,000 mi

Symptoms: Clunking when shifting from park to drive, Visible transmission fluid leaks under vehicle, Excessive vibration at idle, Transmission overheating, Hard shifts or delayed engagement

Fix: Rubber transmission mounts deteriorate allowing excessive movement and stressing cooler lines. Failed cooler lines spray ATF onto hot exhaust creating fire risk. Mount replacement takes 2-3 hours, cooler lines add another 2-4 hours depending on which lines fail. Often addressed together during transmission service.

Estimated cost: $600-1,400

Typical onset: 90,000-150,000 mi

Symptoms: Rough idle and stalling, Hard starting when engine is hot, Poor fuel economy, Hesitation on acceleration, Check engine light with fuel mixture codes

Fix: TBI injectors clog or wear out, throttle position sensor fails, idle air control valve sticks. Parts are increasingly scarce for this system. Throttle body rebuild or replacement takes 3-5 hours including diagnostics. Fuel filter clogging accelerates injector problems and should be replaced every 15,000 miles on these vehicles.

Estimated cost: $800-1,500

Symptoms: Digital instrument cluster flickering or dead, Inaccurate fuel gauge or speedometer, Climate control unresponsive or stuck on one setting, Loss of all dashboard illumination

Fix: Cadillac's digital modules from this era suffer capacitor failures and circuit board degradation. Repair requires specialized electronics work or used module replacement. Dashboard removal takes 4-6 hours. Climate control module is 2-3 hours. Parts availability is poor; many owners convert to analog gauges.

Estimated cost: $600-1,800