why does my BMW 5 Series G30/G31 (2017-2024) make a knocking noise when starting

Solution

1. Preparation

• Tools Required: OBD-II scanner, mechanic's stethoscope, socket set, torque wrench.
• Safety Warnings: Disconnect the battery before working on electrical systems.

2. Engine Oil Check

• Sub-steps:
  1. Remove the engine oil dipstick and check the oil level.
  2. Inspect oil for metal shavings or contaminants.
  3. If oil is low or contaminated, drain and replace with manufacturer-recommended oil.

3. Inspect and Replace Engine Mounts (if damaged)

• Sub-steps:
  1. Raise the front of the vehicle with jack stands.
  2. Remove any coverings to access the engine mounts.
  3. Inspect mounts for cracks or separation; replace if necessary.
  4. Torque the new mounts to manufacturer specifications.

4. Timing Chain/Belt Inspection

• Sub-steps:
  1. Remove any engine covers to access the timing chain/belt.
  2. Check for tension and wear; replace if it appears slack or damaged.
  3. If replacement is necessary, follow specific torque specifications for the timing components.

5. Starter Motor Inspection

• Sub-steps:
  1. Disconnect the battery and remove the starter motor.
  2. Inspect the starter for wear or damage, including the gear and housing.
  3. If faulty, replace the starter motor with a new one and ensure proper alignment when reinstalling.