This is an increasingly common problem these days!Often hard to diagnose since the symptoms can be vague and intermittant but nevertheless potentially extremly damaging.
I have come across this on;
BMW
Jaguar
Rover
VW
Vauxhaul
Peugeot.
And others
Sometimes the prob is clearly due to poor maintenance (corroded steel impellors falling off the drive shaft or just falling to pieces) but mostly it is plastic impellors splitting or coming loose on engines that have clearly been cared for.
Sorry This is just plain bad design/manufacture There is *no* excuse! you "NEVER" had this sort of problem when I first started in mechanics
I have had numerous blown head gaskets as a consiquence of this fault.
Whilst the work is welcome, I feel for the owners and consider them to have been ill used by the manufacturers.
I am also saddened to see otherwise sound vehicles go to the breakers as a consequence of this sort of failure.
Paul