my BMW X3 F25 (2011-2018) has a knocking noise on startup, what could it be

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, engine oil, oil filter wrench, multimeter.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Engine Oil

• Sub-steps:
  1. Raise the vehicle using a jack and secure it on jack stands.
  2. Remove the oil drain plug using a socket wrench and let the used oil drain completely into a container.
  3. Replace the oil filter using an oil filter wrench.
  4. Install a new oil filter and ensure it is tightened to manufacturer specifications.
  5. Reinstall the oil drain plug and torque it to the specified value (typically around 25-30 Nm).
  6. Add new engine oil (refer to owner's manual for specifications) and check the level with the dipstick.

3. Inspect Timing Chain/Belt

• Sub-steps:
  1. Remove any necessary components (e.g., engine covers) to access the timing chain/belt.
  2. Check for slack or wear in the timing chain/belt; replace if damaged.
  3. Reinstall any removed components and torque them to specification.

4. Check and Replace Engine Mounts (if necessary)

• Sub-steps:
  1. Support the engine from below using a jack with a wooden block to avoid damage.
  2. Remove the bolts securing the engine mounts to the frame and engine.
  3. Replace the damaged mounts with new ones and torque the bolts to the specified settings.
  4. Lower the engine and remove the jack.