the water pump cycles through the engine and cools it to a safe level without it the water heats up and will start to boil you will blow a head gasket in a matter of a few blocks and it will do damage to almost everything in the engine DON'T DRIVE A OVERHEATING VEHICLE
You will blow your head gasket. The water pump is designed to keep your engine cool by pumping water thru channels in your engine block and without it it will not take long for your engine to overheat. You run the risk of completely destroying your motor. Water pumps are a farely inexpensive part 60-150 bucks and are pretty easy to replace in about 1 hour. as long as your not driving a BMW or something like that.
The water pump shaft seal could fail totally at any time. So if you don't want to risk expensive engine damage, you might as well have it fixed now. If your engine timing belt drives the water pump, you may need to replace the timing belt and tensioner as well.
Depends on how bad it is. I had a leaking one for about a month before I took it in. I just kept adding water. So it realy depends on what is bad, the bearings, or the impeller. If it overheats, thats a problem and will blow your engine.
How do you know if it's bad? Either you've had it diagnosed as such and you know the engine will overheat, or you don't, in which case, try taking out the thermostat (and bolting back up). If the engine is slow to warm up - replace the thermostat.
