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2006 Cadillac STS

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By Research the Car 5 min read

The 2006 Cadillac STS is a mid-size luxury sedan that aimed to offer a blend of performance and comfort. It was available with three engine options: a 3.6L V6 producing 255 horsepower and 252 lb-ft of torque, a 4.6L Northstar V8 generating 320 hp and 315 lb-ft of torque (RWD), or a detuned version with 315 hp for AWD, and a 4.4L Supercharged Northstar V8 making 469 hp and 439 lb-ft of torque (STS-V). All engines were paired with a 5-speed automatic transmission, with the exception of the STS-V with a 6-speed automatic transmission. Owners often praised the STS for its comfortable ride, spacious interior, and attractive styling, as well as the performance of the V8 engines. Common complaints revolved around electrical issues, the complex Northstar engine design making repairs challenging, and some reliability concerns.

Engine

3.6L V6

  • Timing Chain Wear
    • Description/Symptoms: Rattling noise on startup, check engine light with codes related to camshaft timing. The timing chains stretch, causing inaccurate camshaft timing.
    • Solution: Replacement of timing chains, guides, and tensioners.
    • Estimated Cost to Fix: $1,500 - $2,500+
    • Recalls: None Found
  • High Pressure Fuel Pump Failure
    • Description/Symptoms: Extended cranking, stalling, loss of power.
    • Solution: High pressure fuel pump replacement
    • Estimated Cost to Fix: $400 - $700
    • Recalls: None Found

4.6L Northstar V8

  • Head Gasket Failure
    • Description/Symptoms: Overheating, coolant loss, white smoke from exhaust, milky oil. This is a known weakness of the Northstar engine design.
    • Solution: Head gasket replacement, often requiring specialized tools and expertise due to the engine’s design. Often also requires cylinder head resurfacing and stud replacement.
    • Estimated Cost to Fix: $3,000 - $6,000+
    • Recalls: None Found
  • Oil Consumption
    • Description/Symptoms: Low oil level, blue smoke from exhaust.
    • Solution: Depending on the severity, the fix can range from using a heavier weight oil to piston ring replacement. Often times the cause is unknown and is attributed to the design of the engine.
    • Estimated Cost to Fix: $500 - $5,000+
    • Recalls: None Found

4.4L Supercharged Northstar V8

  • Supercharger Intercooler Pump Failure
    • Description/Symptoms: Loss of power, overheating under boost, check engine light.
    • Solution: Replacement of the supercharger intercooler pump.
    • Estimated Cost to Fix: $500 - $1000+
    • Recalls: None Found
  • Head Gasket Failure
    • Description/Symptoms: Overheating, coolant loss, white smoke from exhaust, milky oil. This is a known weakness of the Northstar engine design.
    • Solution: Head gasket replacement, often requiring specialized tools and expertise due to the engine’s design. Often also requires cylinder head resurfacing and stud replacement.
    • Estimated Cost to Fix: $3,000 - $6,000+
    • Recalls: None Found

Transmission

5L40-E 5-Speed Automatic (3.6L V6 & 4.6L Northstar V8)

  • Valve Body Issues
    • Description/Symptoms: Harsh or erratic shifting, slipping between gears, delayed engagement.
    • Solution: Valve body replacement or rebuild.
    • Estimated Cost to Fix: $800 - $2,000+
    • Recalls: None Found
  • Torque Converter Failure
    • Description/Symptoms: Shuddering, stalling, abnormal noise.
    • Solution: Torque Converter replacement.
    • Estimated Cost to Fix: $700 - $1,500+
    • Recalls: None Found

6L80 6-Speed Automatic (4.4L Supercharged Northstar V8 - STS-V)

  • Valve Body Issues
    • Description/Symptoms: Harsh or erratic shifting, slipping between gears, delayed engagement.
    • Solution: Valve body replacement or rebuild.
    • Estimated Cost to Fix: $800 - $2,000+
    • Recalls: None Found
  • Torque Converter Failure
    • Description/Symptoms: Shuddering, stalling, abnormal noise.
    • Solution: Torque Converter replacement.
    • Estimated Cost to Fix: $700 - $1,500+
    • Recalls: None Found

Suspension

  • Magnetic Ride Control (MRC) Shocks Failure
    • Description/Symptoms: Bouncy or unstable ride, fluid leaking from shocks, “Service Suspension System” message on the dashboard. These shocks are known to fail with age.
    • Solution: Replacement of the MRC shocks.
    • Estimated Cost to Fix: $500 - $1,000+ per shock (parts and labor).
    • Recalls: None Found
  • Air Ride Suspension Compressor Failure (If equipped)
    • Description/Symptoms: The rear suspension is sagging or bottoming out. Air compressor not turning on.
    • Solution: Replacement of the air compressor.
    • Estimated Cost to Fix: $500 - $1,000+
    • Recalls: None Found

Electrical

  • Battery Drain
    • Description/Symptoms: Car battery dies overnight or within a few days of sitting. Parasitic draw from various modules.
    • Solution: Diagnosis to identify the source of the draw and repair/replace the faulty component.
    • Estimated Cost to Fix: $100 - $500+ (depending on the source)
    • Recalls: None Found
  • Navigation/Infotainment Screen Failure
    • Description/Symptoms: Screen goes blank, flickers, or displays incorrect information.
    • Solution: Replacement of the screen or the entire infotainment unit.
    • Estimated Cost to Fix: $300 - $1,000+
    • Recalls: None Found
  • Keyless Entry/Remote Start Issues
    • Description/Symptoms: Key fobs stop working, remote start fails, or the car is difficult to unlock.
    • Solution: Replacement of key fobs, reprogramming, or replacement of the receiver module.
    • Estimated Cost to Fix: $100 - $400+
    • Recalls: None Found

Exterior

  • Sunroof Issues
    • Description/Symptoms: Sunroof gets stuck, makes noise when opening or closing, or leaks.
    • Solution: Sunroof track repair, motor replacement, or seal replacement.
    • Estimated Cost to Fix: $200 - $800+
    • Recalls: None Found

Interior

  • Heated/Cooled Seat Malfunction
    • Description/Symptoms: Seats no longer heat or cool, or only work intermittently.
    • Solution: Replacement of the heating/cooling element, blower motor, or control module.
    • Estimated Cost to Fix: $200 - $600+ per seat
    • Recalls: None Found
  • Dashboard Cracking
    • Description/Symptoms: Cracks appearing on the dashboard, particularly in sun-exposed areas.
    • Solution: Replacement of the dashboard or installation of a dashboard cover.
    • Estimated Cost to Fix: $300 - $1,500+
    • Recalls: None Found

Summary:

The 2006 Cadillac STS can be a comfortable and stylish vehicle, but potential buyers should be aware of some common issues. The Northstar engines, while powerful, are prone to head gasket failures and oil consumption, which can be costly to repair. Electrical problems and suspension issues, particularly with the MRC system, are also frequently reported. Transmission issues can also arise. Overall, while many of these issues are not catastrophic, they can lead to significant repair bills, so a thorough inspection before purchase is recommended.

Cadillac, STS
Cadillac STS 2006
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