The "new" pump is now a piece of junk and has to be replaced. Buy a M-B
remanufactured pump from the dealer; it won't be much more expensive
than the gypsy pump that's in the car now. The grinding is from the
current pump which may have been defective or run dry after the
radiator's leak. No heat could be due to a broken pump, an air lock or
The pump has to come out.