My late Series 1 2.0i from 1993 has a leaky LHM pump.

It’s proving difficult to replace as it appears to be a rather rare kind. It’s distinguishing feature appears to be 3 connections rather than the two which all the possible replacement parts have (I’m waiting on pictures) come with.

What is this strange pump that apparently no other XMs seem to have had. Did the late series 1s have an improved setup but that then got obseleted by the time of the anti sink Y4.

Is there a timeline of the XM variations of hydractive and how it evolved across the models anywhere for reference?