The bolts in question are the three that hold the pump to the bracket.
1 bolt has been missing for a while, the plate was rusty.
Another has recently vanished, the plate was still shiny where the bolt head should have been.
The third snapped off flush with the pump.
A small piece of the pump housing from around one of the threaded holes was also missing.
I had a spare pump that we decided to install.
Easy fix, got lucky with undoing the viscous though. Not the easiest without a fan belt to hold the pulley.
Everything seems to be in order with the rest of the pulleys etc.
Possibly the bolts were never torqued up and just came loose over time.

