Similar issues regarding rear windscreen wiper and washer turning on intermittently, and drips of rusty water running out. I removed the tailgate trim, which is held on by two screws with star shaped heads underneath the emergency triangle storage box, and also by press in clips, which pull out fairly easily. The electrical connector and the hose clip are easily removed. I removed the base plate for the wiper motor assembly and washer spigot (very small star bits). It was full of rusty sludge. I cleaned it up and also cleaned the washer nozzles, using fine brushes. I reassembled it. On test, it leaked. I dismantled and re-evaluated.The washer fluid hose connects to a plastic spigot attached to the base plate, which in turn connects to the metal spigot that feeds the washer jets at the base of the wiper arm. When pressure builds up behind the nozzles, due to fouling, the plastic rather than the metal gives way and stretches slightly. Then the pressure of normal operation squeezes some washer fluid between the central spigot and its connector. I wrapped the metal spigot with a turn and a half of self amalgamating rubber tape and reassembled. The leak has stopped. The washer operates normally. The wiper operates normally, switches on and off when operated and stops at the correct point. Note that I would have preferred to work on the unit at the bench but the spline connector for the wiper base has rusted in. In my view it is a bad design to run water through the middle of an electromechanical device using press on fittings rather than securing the fluid tubing with pressure resistant connectors. The design is worse because it mates plastic and metal.