1989 CADILLAC SEVILLE

Typical onset: 60,000-100,000 mi

Symptoms: Excessive oil consumption (1 qt per 500-1000 miles), White smoke from exhaust, Coolant in oil (milky dipstick), Overheating despite new thermostat/radiator, Loss of compression in multiple cylinders

Fix: The aluminum block develops porosity and cracks between cylinders, especially cylinders 3-6. Head gasket replacement is temporary at best. Real fix requires complete engine replacement or rebuild with aftermarket block sleeves. Expect 18-25 labor hours for R&R plus rebuild time. Many shops won't touch these—find a specialist or swap to Northstar if you're committed.

Estimated cost: $4,500-8,000

Typical onset: 70,000-120,000 mi

Symptoms: Hard starting when warm, Stalling at idle or when coming to stops, Surging at highway speeds, Check Engine Light with codes 34 or 44, Fuel smell from engine bay

Fix: The TBI unit develops internal leaks, and the injectors clog or fail. Fuel pressure regulator diaphragm ruptures, dumping fuel into vacuum lines. Complete TBI rebuild or replacement needed, along with fuel filter and often the in-tank pump. 4-6 hours labor if pump is included.

Estimated cost: $800-1,500

Typical onset: 80,000-130,000 mi

Symptoms: Transmission fluid puddles under car, Pink or red fluid on ground, Transmission slipping or delayed engagement, Overheating transmission, Fluid level drops rapidly

Fix: The steel cooler lines rust through where they run along the frame rail, especially in salt states. If not caught early, low fluid destroys the TH440-T4 transmission. Replace both lines (they're cheap), flush cooler, refill with Dexron. If transmission already damaged, you're looking at rebuild. Lines alone: 2-3 hours. Transmission rebuild adds 12-16 hours.

Estimated cost: $300-600 (lines only), $2,200-3,500 (with transmission rebuild)

Typical onset: 80,000-140,000 mi

Symptoms: Severe vibration at idle, Rubber ring separating from pulley, Squealing serpentine belt that won't stay tight, Crankshaft position sensor codes, Visible wobble on front of crankshaft pulley

Fix: The rubber isolation ring in the balancer breaks down, allowing the outer ring to separate. If it comes apart while driving, you lose all accessories and risk crankshaft damage. Replacement requires special puller and installer tools. 2-3 hours labor. Do NOT drive if you see separation starting.

Estimated cost: $400-700

Symptoms: Intermittent or complete gauge blackout, Flickering displays, Incorrect readings (speedometer, fuel, temp), Climate control display dead, Only works when dash is tapped

Fix: Cold solder joints on the circuit boards crack over time. The vacuum fluorescent displays also fail. Dash removal and rebuild with resoldering required, or send to specialist. Many owners convert to analog gauge clusters from later models. 3-4 hours to remove and reinstall dash, plus rebuild time.

Estimated cost: $400-900 (professional rebuild), $150-300 (DIY resolder)

Typical onset: 90,000-150,000 mi

Symptoms: Severe clunk when shifting from Park to Drive or Reverse, Vibration at idle in gear, Exhaust hitting floorpan, Visible engine/trans sag when viewed from side

Fix: The rear transmission mount rubber deteriorates, allowing the powertrain to drop and torque excessively. This accelerates cooler line wear and can crack exhaust. Replacement requires transmission support while swapping mount. 1.5-2 hours labor. Replace front engine mounts at same time if original.

Estimated cost: $250-450