2004 CADILLAC SEVILLE STS

Typical onset: 80,000-150,000 mi

Symptoms: White smoke from exhaust on cold start, Coolant loss with no visible leaks, Overheating under load or climbing grades, Coolant in oil (milky dipstick) in severe cases, Misfires and rough idle as gaskets deteriorate

Fix: The aluminum block's head bolt threads strip or pull out, requiring either Timesert thread repair (8-12 hrs labor) or full engine removal for proper machine work (20+ hrs). Many shops won't warranty in-chassis repairs. Includes new head gaskets, bolts, timing components, and coolant system flush.

Estimated cost: $3,500-6,500

Typical onset: 100,000-180,000 mi

Symptoms: Burning 1+ quart of oil every 500-800 miles, Blue smoke on acceleration, Rod knock or main bearing rumble at idle, Low oil pressure warning at operating temp, Catastrophic engine failure if oil level drops critically

Fix: Worn piston rings allow oil past into combustion chambers. Owners who don't monitor oil levels starve the bottom end. Requires engine removal, full teardown, new pistons, rings, bearings, and machine work. Most opt for reman long block (18-24 hrs R&R).

Estimated cost: $6,000-9,500

Typical onset: 70,000-120,000 mi

Symptoms: Transmission fluid leaking at radiator connections, Pink fluid puddles under front of vehicle, Transmission slipping or delayed engagement if fluid level drops, Overheating transmission if coolant contaminates ATF

Fix: Steel cooler lines rust through at crimped fittings or where they pass through subframe. Replacement requires raising vehicle, sometimes dropping subframe for access (3-5 hrs). Replace both feed and return lines as preventive measure.

Estimated cost: $400-800

Typical onset: 90,000-140,000 mi

Symptoms: Clunk or thud when shifting from Park to Drive or Reverse, Excessive vibration at idle in gear, Visible sag or separation of rubber mount on inspection, Driveline shudder during acceleration

Fix: Hydraulic transmission mount fails, allowing excessive powertrain movement. Requires lift access and support of transmission/engine during swap (2-3 hrs). OEM mount recommended over cheap aftermarket.

Estimated cost: $300-550

Typical onset: 80,000-130,000 mi

Symptoms: Clunking over bumps from front end, Steering wander or imprecise tracking, Uneven inside tire wear, Loose or rattling feel through steering wheel

Fix: Rubber bushings in lower control arms deteriorate and tear. Requires pressing out old bushings and installing new ones, or replacing entire control arms (2.5-4 hrs per side). Alignment mandatory after replacement.

Estimated cost: $600-1,200

Symptoms: Clicking or ticking noise from behind dashboard, Heat stuck on one side, AC on the other, Temperature control unresponsive or erratic, Constant cycling noise while driving

Fix: Plastic gear teeth strip inside actuator motor. Access varies by location—some require dash disassembly, others reachable from under hood or glove box area (1-4 hrs depending on which actuator). Multiple actuators control different zones.

Estimated cost: $250-650