When mine broke,the pump "locked up" the pump shaft/pulley angled about 10-15 degrees due to the engine still running, causing the belt to slip off. The ensuing loss of power steering & alternator caught me off guard. Luckily I was only 3 blocks from home. Felt like an old NASCAR stocker without power steering!
Upon removing the water pump (more involved as you all well know, Series 1) I found that the front cover that the water pump bolts to, has a gouge from the impeller when the shaft angled. Needless to say, I didn't want to fix that at this time, it'* a more major project to replace the front cover (I might have tried JB Weld!), so I just installed another rebuilt pump. The end result is that the Bonnie runs a little hotter on the temp gage, probally from coolant bypassing thru the groove cut by the impeller.