my BMW 3 Series E90/E91 (2005-2012) has a knocking noise from the engine what is it

Solution

1. Preparation

• Gather tools and parts: Ensure that you have the necessary tools such as a socket set, torque wrench, and oil filter wrench.
• Disconnect the battery: Always disconnect the negative terminal to prevent electrical shorts.

2. Inspect and Replace Engine Oil

• Drain the old oil:
  • Position a drain pan under the oil pan.
  • Remove the drain plug and allow the oil to completely drain.
• Replace the oil filter:
  • Use an oil filter wrench to remove the old filter.
  • Apply a small amount of new oil to the rubber seal of the new filter before installing.
  • Install the new filter and tighten it by hand.
• Add new engine oil:
  • Replace the drain plug and tighten it to the manufacturer's torque specification (usually around 25-30 ft-lbs).
  • Fill the engine with the recommended type and amount of engine oil (refer to the owner’s manual, typically 5W-30 or 0W-40).

3. Inspect Engine Components

• Check for worn or damaged components:
  • Remove the valve cover to inspect the valvetrain for wear or damage.
  • Look for signs of damage on rocker arms or lifters.
• Replace any worn components:
  • If any parts are found to be damaged (e.g., lifters, timing chain), replace them accordingly.

4. Test Drive

• Reassemble everything: Ensure all components are reinstalled correctly.
• Reconnect the battery and start the engine.
• Perform a test drive to check if the knocking noise persists under various driving conditions.