Water pump problem?

[gman]

What is typically the first signs of a water pump problem? My '72 makes extremely low rumbling noises when its running. Can't hear them when driving but only at idle. Not to say it isn't rumbling then too, just that I can't hear them over the normal road noise. It isn't constant.......will rumble for 15 seconds then stops or almost goes away.......then starts rumbling again.........but it almost always begins when stopped and idling. You can feel it too. Or maybe power steering pump? Doesn't seem to change when turning steering wheel though. Any ideas? Very annoying to say the least. Thanks everyone. By the way.......truck does not overheat....as a matter of fact, damn near doesn't move from the cold line ever. Haven't pulled 'stat yet. ?????????