Abstract: Hydraulic systems comprising master and servo cylinder assemblies are sometimes bled only with difficulty, and even then not effectively.The invention provides a method of bleeding such systems, which involves the introduction of hydraulic fluid into the servo cylinder via a hydraulic connector having a fluid feed passage and a non-return valve therein. The fluid passes from the servo cylinder into the master cylinder. The hydraulic connector has engaging means for engaging with a connecting member of a hydraulic fluid feed line. A removable dust cap co-operates with the engaging means to seal off the passage and to protect it against dust and foreign matter when the engaging means is not connected to the connecting member.