23mm bolt on top side. I will tighten and see what happens.
:most likely is coming from the crimped hose assembly (in the upper left of your picture). There could also be a leak from the shaft seal of the pump, but stick with investigating the hoses for now. :I suggest putting some extra turns on all the clamps and then wiping everything off as much as possible. Then check the area again within a week or so (depending on how much driving you do). This may help you pinpoint the leak. :Dave