2017 BMW 420i

The 2017 BMW 420i is a stylish and sporty coupe, gran coupe, or convertible known for its agile handling and refined driving experience. The 420i comes with a 2.0-liter turbocharged four-cylinder engine producing 180 horsepower and 200 lb-ft of torque. Other engine options available on the 4 Series platform for 2017 include the more powerful 430i with a higher-output version of the 2.0-liter turbo-four, and the 440i with a 3.0-liter turbocharged inline-six. Transmission choices were primarily an 8-speed automatic, although a 6-speed manual was available on some models. Owners generally appreciate the 420i’s elegant design, comfortable interior, and engaging driving dynamics. However, some criticisms include the relatively high cost of ownership, somewhat cramped rear seats (especially in the coupe), and the potential for certain reliability issues.

Engine

2.0L Turbocharged Four-Cylinder (N20/B48)

• Oil Leaks
  • Description/Symptoms: Oil leaks can develop from various locations including the valve cover gasket, oil filter housing gasket, and oil pan gasket. Symptoms include visible oil leaks, a burning oil smell, and low oil levels.
  • Solution: Replacing the faulty gasket or seal.
  • Estimated Cost to Fix: $150 - $500+ depending on the location of the leak.
  • Recalls: None Found
• Timing Chain Issues (Primarily N20 Engine)
  • Description/Symptoms: The N20 engine is known to have issues with the timing chain wearing prematurely and potentially breaking. This can cause significant engine damage. Symptoms include a rattling noise from the engine, especially on startup, and potential engine misfires or stalling.
  • Solution: Replacing the timing chain, guides, and tensioner.
  • Estimated Cost to Fix: $1,000 - $2,500+
  • Recalls: None Found
• Coolant Leaks
  • Description/Symptoms: Coolant leaks can occur from the water pump, hoses, or expansion tank. Symptoms include a coolant leak under the vehicle, overheating, and low coolant levels.
  • Solution: Replacing the faulty water pump, hoses, or expansion tank.
  • Estimated Cost to Fix: $200 - $800+ depending on the component.
  • Recalls: None Found

Transmission

8-Speed Automatic (ZF 8HP)

• Rough Shifting/Hesitation
  • Description/Symptoms: Some owners report rough or jerky shifting, particularly between certain gears. Hesitation during acceleration may also be noticed. This can be caused by worn valve body components or degraded transmission fluid.
  • Solution: A transmission fluid flush and software update might resolve the issue. In more severe cases, valve body replacement or complete transmission overhaul may be necessary.
  • Estimated Cost to Fix: $300 - $3,000+ depending on the repair.
  • Recalls: None Found
• Mechatronic Unit Failure
  • Description/Symptoms: The mechatronic unit controls the shifting functions of the transmission. Failure can lead to erratic shifting, transmission slippage, or complete loss of drive.
  • Solution: Replacement of the mechatronic unit or valve body assembly
  • Estimated Cost to Fix: $2,000 - $4,000+
  • Recalls: None Found

Suspension

• Noises (Clunking/Squeaking)
  • Description/Symptoms: Owners have reported clunking or squeaking noises coming from the suspension, particularly when going over bumps. This could be due to worn control arm bushings, sway bar links, or shock absorbers.
  • Solution: Replacing the worn bushings, links, or shocks.
  • Estimated Cost to Fix: $200 - $800+ per corner depending on the component.
  • Recalls: None Found

Electrical

• Battery Drain
  • Description/Symptoms: Some owners experience excessive battery drain, leading to difficulty starting the vehicle or a completely dead battery. This can be caused by a faulty module not entering sleep mode or a parasitic draw from an aftermarket accessory.
  • Solution: Diagnose and repair the source of the parasitic draw. This may involve replacing a faulty module or removing/repairing aftermarket accessories.
  • Estimated Cost to Fix: $100 - $1,000+ depending on the cause.
  • Recalls: None Found
• iDrive System Issues
  • Description/Symptoms: The iDrive infotainment system can experience glitches, freezes, or complete failures. This may require software updates or, in severe cases, replacement of the iDrive control unit.
  • Solution: Software update or iDrive control unit replacement.
  • Estimated Cost to Fix: $100 (Software Update) - $1,500+ (Control Unit Replacement)
  • Recalls: None Found

Exterior

• Door Handle Issues
  • Description/Symptoms: The door handles, particularly those with comfort access, can sometimes fail to function properly. This can manifest as difficulty opening the door or the handle not retracting completely.
  • Solution: Replacement of the door handle assembly.
  • Estimated Cost to Fix: $300 - $700+ per handle.
  • Recalls: None Found

Interior

• Seat Heater Failure
  • Description/Symptoms: The seat heaters may stop working, either partially or completely. This can be due to a faulty heating element or a problem with the control module.
  • Solution: Replacing the heating element or control module.
  • Estimated Cost to Fix: $200 - $600+ per seat.
  • Recalls: None Found

Summary

The 2017 BMW 420i, while generally a well-regarded vehicle, does have some common issues. Engine oil leaks and potential timing chain problems (especially with the N20 engine) can be costly. The ZF 8-speed transmission can also exhibit issues like rough shifting or mechatronic unit failure. Electrical gremlins, like battery drain or iDrive malfunctions, can also occur. While some issues are relatively minor and inexpensive to fix, others can be quite costly. Prospective buyers should be aware of these potential problems and have the vehicle thoroughly inspected before purchasing.