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2021 BMW M340i

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By Research the Car 4 min read

The 2021 BMW M340i is a performance-oriented version of the popular 3 Series sedan, known for its blend of luxury, sportiness, and daily usability. The main engine option for the 2021 M340i is the B58 3.0-liter turbocharged inline-six, producing 382 horsepower and 369 lb-ft of torque. This engine is paired with an 8-speed automatic transmission. While praised for its powerful engine, sharp handling, and luxurious interior, some owners have reported issues related to various components, including the engine, transmission, and electrical systems. Some common dislikes include the run-flat tires and sometimes a stiff ride.

Engine

B58 3.0L Turbocharged Inline-Six

  • Coolant Leaks
    • Description/Symptoms: Coolant leaks often originate from the plastic coolant expansion tank, hoses, or the water pump housing. Symptoms include low coolant levels, overheating, and visible coolant puddles under the car.
    • Solution: Replacing the faulty component (expansion tank, hose, water pump).
    • Estimated Cost to Fix: $200 - $800+ depending on the component.
    • Recalls: None Found
  • Oil Filter Housing Gasket Leaks
    • Description/Symptoms: Oil leaks are a common issue on B58 engines with the oil filter housing gasket beginning to leak. Symptoms include burning oil smell and low oil levels.
    • Solution: Replace the oil filter housing gasket.
    • Estimated Cost to Fix: $200-$500
    • Recalls: None Found
  • High Pressure Fuel Pump (HPFP) Failure
    • Description/Symptoms: Potential fuel delivery issues. Can cause rough running or failure to start.
    • Solution: Replacement of the high-pressure fuel pump.
    • Estimated Cost to Fix: $1,000 - $2,000+
    • Recalls: None Found

Transmission

8-Speed Automatic (ZF 8HP)

  • Rough or Delayed Shifts
    • Description/Symptoms: Some owners have reported experiencing rough or delayed shifts, especially during cold starts or under heavy acceleration. This can sometimes be attributed to low transmission fluid levels or degradation of the fluid.
    • Solution: Transmission fluid flush or replacement and software update may resolve the issue. If problem persists then transmission replacement may be required.
    • Estimated Cost to Fix: $300 - $800+ for fluid flush and software update. Transmission replacement can be several thousand dollars.
    • Recalls: None Found
  • Torque Converter Issues
    • Description/Symptoms: Some owners have reported issues with the torque converter, which may manifest as shuddering or vibrations at certain speeds, especially when the transmission is locking and unlocking the torque converter.
    • Solution: Replacement of the torque converter.
    • Estimated Cost to Fix: $1,500 - $3,000+
    • Recalls: None Found

Suspension

  • Adaptive Suspension Malfunctions (if equipped)
    • Description/Symptoms: If the vehicle is equipped with adaptive suspension (Adaptive M Suspension), some owners have experienced malfunctions, leading to error messages or a noticeable difference in ride quality.
    • Solution: Diagnosis and replacement of faulty sensors or dampers.
    • Estimated Cost to Fix: $500 - $2,000+ per damper or sensor.
    • Recalls: None Found

Electrical

  • Software Glitches/iDrive Issues
    • Description/Symptoms: The iDrive infotainment system can experience software glitches, including freezing, slow response times, or connectivity problems with Apple CarPlay or Android Auto.
    • Solution: Software updates or module replacement.
    • Estimated Cost to Fix: $0 if software update is available and performed by the dealer. $300 - $1,500+ for module replacement.
    • Recalls: None Found
  • Sensor Failures
    • Description/Symptoms: Issues with various sensors (e.g., parking sensors, tire pressure sensors) can occur, leading to warning lights on the dashboard.
    • Solution: Diagnosis and replacement of the faulty sensor.
    • Estimated Cost to Fix: $100 - $500+ per sensor.
    • Recalls: None Found

Exterior

  • No Issues Found

Interior

  • Rattling/Creaking Noises
    • Description/Symptoms: Some owners have reported rattling or creaking noises coming from the dashboard or other interior trim pieces.
    • Solution: Tightening or replacing loose trim pieces, applying felt tape to contact points.
    • Estimated Cost to Fix: $50 - $300+ depending on the complexity of the repair.
    • Recalls: None Found
  • Seat Motor Malfunctions
    • Description/Symptoms: Issues with the electric seat motors, leading to limited or no movement of the seats.
    • Solution: Replacement of the faulty seat motor or switch.
    • Estimated Cost to Fix: $300 - $1,000+ per seat.
    • Recalls: None Found

Summary

The 2021 BMW M340i is a well-regarded performance sedan, but some owners have reported issues with the engine, transmission, suspension, electrical system, and interior. Engine issues, particularly coolant leaks and oil filter housing leaks, appear to be relatively common. Transmission problems like rough shifting and torque converter issues can be more significant and costly to repair. Electrical glitches and interior rattles are also potential concerns. While the issues listed are not all-encompassing and do not affect all vehicles, prospective buyers should be aware of these potential problems and consider a thorough inspection before purchasing. The severity and cost of these issues can vary, but addressing them promptly can help maintain the M340i’s performance and reliability.

BMW, M340i
BMW M340i 2021
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