How to avoid diesel fuel leaks

How to avoid diesel fuel leaks

Following feedback from our technical team it’s been identified that fuel leakage from some VAG vehicle diesel filter housings may occur subsequent to fuel filter element replacement.

Due to the position of the fuel filter in the engine compartment, leakage of fuel from the filter housing may subsequently compromise safety and cause engine component damage.

While the integrity of the fuel filter housing is sound, incorrect re-installation of the housing cap may cause misalignment between the filter housing cap and housing sealing surfaces and/or deformation of the sealing O-ring, causing diesel fuel leakage.

The most common cause of filter cap/housing misalignment and subsequent fuel leakage, results from the incorrect tightening of the five fixing screws.

If the correct installation procedure is not followed, then external fuel leakage and engine component damage could result. Often diesel leakage, as described here, leads to suspicions that the fuel filter element is to blame. However, as the fuel filter element is mounted entirely within the filter housing, it cannot cause external fuel leakage if the cap is correctly re-installed.

Replacement of the filter element via the following steps will avoid potential fuel leakage:
1. Remove all screws and the housing cap.
2. Remove the used filter element and sealing O-ring.
3. Remove all diesel/dirt/water residue from the housing using a diesel suction tool.
4. Install a new MANN-FILTER fuel filter element.
5. Wet the new O-ring with diesel fuel and mount it onto the cap.
6. Offer the cap squarely to the housing and push down evenly until sealed centrically.
7. Install and turn all screws down by hand.
8. Tighten all screws in the correct sequence (see diagram, below), to a torque of 5Nm – this is a very important step!


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