Humming/Growling Noise from Rear of 2018 Impreza Sport - Wheel Bearing?

ClearTheCode admin answer:

Your description of a humming or growling noise from the rear that changes with speed and when turning is a classic symptom of a failing wheel bearing. This is a relatively common wear item on many vehicles, including the 2018 Subaru Impreza, especially as they approach and exceed 70,000 miles.

Here's what you need to know:

1. Symptoms of a Bad Wheel Bearing:

   • Humming/Growling Noise: The most common symptom, often described as sounding like a drone or a low rumble.
   • Noise Changes with Speed: The pitch and volume typically increase with vehicle speed.
   • Noise Changes When Turning: The noise often gets louder when turning in one direction (loading the bad bearing) and quieter when turning in the opposite direction.
   • Vibration: In more severe cases, you might feel a vibration through the steering wheel or floorboards.
   • Loose Wheel: In extreme cases, there might be noticeable play in the wheel when the car is jacked up.

2. Causes:

   • Wear and Tear: Wheel bearings are constantly under stress from vehicle weight, road impacts, and rotational forces. Over time, the grease can break down, and the internal components wear out.
   • Impact Damage: Hitting potholes, curbs, or other road debris can accelerate bearing failure.
   • Corrosion: Exposure to water and road salt can degrade the bearing's seals and internal components.

3. How to Confirm (Professional Diagnosis):

   • A mechanic will typically lift the vehicle and spin the wheels by hand, listening for the characteristic grinding or rumbling sound. They may also check for excessive play by rocking the wheel at the 12 and 6 o'clock positions.
   • Road testing with a chassis ear (a listening device) can pinpoint the exact location of the noise.

4. When to See a Shop:

   • Promptly: A failing wheel bearing is not just annoying; it's a safety concern. While it usually degrades gradually, a severely worn bearing can eventually seize or even cause the wheel to separate from the vehicle in extreme circumstances. It also places undue stress on other suspension components.
   • Schedule an appointment with your trusted mechanic or Subaru dealership soon. They will be able to confirm the diagnosis and replace the faulty bearing.

5. Cost and Replacement:

   • The cost to replace a wheel bearing can vary depending on whether it's just the bearing or a full hub assembly, and labor rates. For an Impreza, you might expect to pay anywhere from $300 to $600+ per wheel, including parts and labor. It's often recommended to replace them in pairs on an axle if one side has failed, though not strictly necessary if the other side is still in good condition. There are no specific OBD codes associated with a failing wheel bearing.