How to change the diesel filter on a Mercedes Vito W639?

To replace the diesel filter on a Mercedes-Benz Vito W639, work with the engine off and the bonnet open, protecting surfaces with rags as diesel may spill during disconnection. Locate the diesel filter assembly at the rear of the engine bay, near the bulkhead.

The top of the filter has connections with pipes and fittings, and you will also see two metal pipes entering the filter head. Before removing the filter, clear access by moving only what restricts space (ducts or nearby covers) without pulling on wiring.

Work on the diesel connections by releasing the locking clips: detach them carefully and disconnect the lines one at a time, keeping them controlled to minimise leaks and prevent contamination. If there are clamps on rubber hoses, loosen them just enough to slide the hose off without forcing it. Once the connections are detached, unclip the filter from its mount and remove it. Install the new filter ensuring it is oriented correctly and seated well in the mount; then reconnect all the diesel lines in their correct positions and reinsert the clips until fully engaged.

Finally, check that the hoses are not under tension and that each connection is fully seated. After replacement, conduct a thorough check for any leaks.

If starting is difficult, allow the system to fill correctly according to the setup procedure (without prolonged cranking) and immediately check the connections: even a small air leak or a connection not fully closed can cause fuel supply issues.