how to diagnose EVAP system leaks in Volkswagen Golf MK5 (2004-2008)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Damaged Components

• Fuel Filler Cap:

  • Remove the fuel filler cap and inspect for cracks or damage.
  • Replace with a new OEM filler cap if necessary.

• EVAP Hoses:

  • Locate all EVAP hoses connected to the charcoal canister and purge valve.
  • Remove any damaged hoses using hose clamps or pliers.
  • Replace with new hoses that meet OEM specifications.

3. Smoke Test

• Setup:

  • Connect a smoke machine to the EVAP service port.
  • Seal off any other openings (like the fuel filler neck) to ensure proper pressure.

• Execution:

  • Activate the smoke machine and observe for smoke escaping from any component in the EVAP system.
  • Identify and mark any leaks found during this test.

• Repair:

  • Repair or replace any leaking components identified during the smoke test, such as the charcoal canister, purge valve, or associated hoses.

4. Reconnect and Test

• Reconnect any components and hoses that were removed.
• Reconnect the battery.
• Clear any engine codes using the OBD-II scanner.

5. Final Verification

• Start the engine and allow it to reach operating temperature.
• Monitor the system for leaks or abnormal readings.
• Conduct a test drive to ensure the check engine light does not reappear.