2006 CADILLAC CTS

Typical onset: 80,000-140,000 mi

Symptoms: Burning 1+ quart of oil every 500-1,000 miles, Blue smoke on startup or acceleration, Fouled spark plugs causing misfires, Check engine light with P0300-series codes, Eventually leads to spun bearings if oil runs low

Fix: Rings are carboning up and losing seal—requires full engine rebuild or short block replacement. We're talking 20-28 hours of labor for a proper teardown, new pistons, rings, bearings, gaskets, timing chains while you're in there. Some shops will try a ring soak treatment but it's a band-aid.

Estimated cost: $4,500-7,500

Typical onset: 70,000-120,000 mi

Symptoms: Pink milkshake in coolant overflow bottle (trans fluid mixing with coolant), Transmission slipping or harsh shifts after coolant contamination, Overheating transmission, Coolant loss with no visible external leak

Fix: The internal cooler lines in the radiator corrode and leak, cross-contaminating fluids. Once it mixes, you need radiator replacement, complete trans fluid flush (sometimes multiple flushes), and often a transmission rebuild if it's been driven contaminated. Catch it early: radiator + lines is 3-4 hours. Miss it: add 12-18 hours for transmission work.

Estimated cost: $800-1,200 (radiator only), $3,500-5,000 (if trans damaged)

Typical onset: 60,000-100,000 mi

Symptoms: Gear oil dripping from rear of driveshaft/differential, Oil spots on garage floor under rear axle, Whining noise from rear end if fluid gets low, Visible wetness around pinion yoke

Fix: The pinion seal dries out and starts weeping. Requires dropping the driveshaft, pulling the yoke, replacing the seal and sometimes the yoke bushing. About 2-3 hours labor. Not a huge job but ignore it and you'll cook the diff bearings.

Estimated cost: $350-600

Symptoms: Security light stays on, car won't start or starts then dies after 2 seconds, Key gets stuck in ignition, Have to wiggle key to get it to turn, Intermittent no-start that clears after 10-minute wait

Fix: GM's Passlock system is garbage—the lock cylinder sensor fails or the wiring corrodes. Sometimes you can get away with a relearn procedure (free, 10 minutes), but often needs lock cylinder replacement (1.5 hours) or bypass module installation (1 hour). Some techs just bypass the whole Passlock system permanently.

Estimated cost: $200-500

Typical onset: 90,000-150,000 mi

Symptoms: Intermittent electrical gremlins—gauges go haywire, wipers act up, Theft deterrent system randomly activates, Turn signals or cruise control stop working, Multiple seemingly unrelated electrical faults

Fix: The CIM controls steering column functions and talks to the BCM—when it fails, you get weird cascading problems. Module is behind the steering column, requires programming after installation. About 2 hours labor plus the module (which can be pricey new, salvage yard units need programming).

Estimated cost: $400-800

Typical onset: 70,000-120,000 mi

Symptoms: Clunk when shifting from Park to Drive/Reverse, Vibration at idle that changes when put in gear, Excessive drivetrain movement felt through shifter, Visible sagging or torn rubber on mount

Fix: The rubber trans mount deteriorates—common on this platform. It's a straightforward job: support the trans, unbolt old mount, bolt in new one. About 1-1.5 hours. Do it before it tears completely and whacks the exhaust.

Estimated cost: $200-350

Typical onset: 100,000-150,000 mi

Symptoms: Car cranks but won't start, no fuel pressure, Intermittent stalling, especially when hot, Sputtering or hesitation under load, Whining noise from rear seat area (pump struggling)

Fix: Pump is in-tank, requires dropping the fuel tank or removing rear seat and cutting an access panel (which most techs do). About 2-3 hours labor. Use AC Delco or equivalent—cheap pumps fail quickly. Also replace the filter while you're there.

Estimated cost: $500-800