Quote Originally Posted by Richard View Post
So does the coolant feed have to be pressurised? (I had hoped not, but....)
It depends on how it's been designed. If it is a venturi, then it should create a vacuum and draw fluid out an unpressurised container.
However it's maybe not a venturi, in which case it does need the fluid to be pressurised.

Only way to find out, is connect it to a suitably regulated air supply, and see if it sucks or not.