Success at last!
Today I drove the Micra up onto ramps. After much contortion (!), and the use of mirrors, I was able to locate an adjustment slot and associated tensioner bolt on the steering pump mounting bracket. (To locate, from above, place a small mirror just above the steering pump pulley, and ‘look’ towards the centre of the engine bay).
In case anyone else has a problem, this is the procedure that I used to adjust the water pump drive belt (for models with power steering and without an idler pulley):
· Slacken the two pivot bolts at the base of the steering pump mounting bracket (access from below).
· Slacken the nut that goes through the adjustment slot (access from above).
· Use the tensioner bolt to adjust the belt (clockwise to tighten – access from below).
· Tighten all the bolts.
Thanks to everyone who tried to help.