Mercedes-Benz W203 high-pressure pump leak
Mercedes-Benz W203 CDI: where does the high-pressure pump leak diesel from?
The most common cause is the pump's hardened O-rings in the fuel line connectors, along with the cover seals. The cover bolts can also work loose over the years, letting diesel run out between the covers. The leak is often bigger when cold than when warm.
Mercedes-Benz W203: how do you fix a high-pressure pump leak?
Usually the pump's seal kit is replaced: the cover seals and the connector O-rings. No special tools are needed, but the inside of the pump must be cleaned carefully and the cover bolts can be tight. It is worth cleaning rust off the cover sealing surfaces.
Mercedes-Benz W203: does replacing just the seals always help?
It often helps, and the low-pressure side O-rings are worth replacing at the same time. Cheap O-rings can start leaking again quickly. A pump that has leaked for a long time may need repair or replacement, and the tightening torques must be followed.