Does it sound similar to this?
If so the impeller assembly is moving inside the casing, sooner or later the blades will touch the metal casing and possibly shatter, maybe even breaking the seals in which case they could make it into the engine causing further damage and you would see smoke and oil makes it where it shouldn't be.
You may find a little black smoke if you have continued to drive it.
Alternatively if it is a split hose you may hear a high pitched whistling possibly