It's a very close fit on the water pump. A little corrosion can make it a very tight fit. Be careful tapping on it and beware that they often turn loose suddenly. When that happens the usually rams straight into the radiator. That will make you unhappy. If you have the radiator out then it's safe, but watch out for your body parts. Fan blades can be sharp. Of course sometimes a clutch just needs a bit of persuading and comes right off like it's supposed to.