Document A6 4B, Fuel Leak at Cylinder Head (Solution)

Fuel leak on the outside of the cylinder head.
V6 TDI engines.

Affected vehicle identification numbers (VINs):
AUZZZ4BZWN000001 - 999999

Cause:
In 4-valve TDI engines, the fuel injectors are necessarily routed vertically through the valve cover and cylinder head, thus being surrounded by engine oil. To prevent extreme oil dilution in case of defective or leaky injectors due to improper installation, horizontal drain holes are led from all injector seats outwards. Without these drain holes, the oil pan would quickly fill up in such a situation, potentially causing the engine to run uncontrollably.
Solution;
If diesel fuel leaks from any of the three bores located on the side of the cylinder head, it is due to a damaged O-ring on the corresponding injector. In this case, the injector must be replaced.