Cracked Vacuum pump housing 1975 240D

[rwogs]

My daughter was driving her car the other night and experienced a clunk/bang and the engine lost power. I discovered that the vacuum pump housing on the right front of the diesel engine (at 3 o'clock) is cracked right by the bolt head (located at about 2 o'clock on the pump) that protrudes and creates a "shoulder" there (I could observe some oil leaking out of it but nothing excessive as she stopped very shortly after it occurred).

I'll remove it this weekend and try and determine what happened. I can see from pictures and diagrams that it has a roller that must ride on a lobe or some other surface to power it. I'm hoping that it is simple metal fatigue and not something worse. It ran until she pulled over and stopped it. I was not able to find this type of problem described on this forum or the vintage forum., Anyone have experience with this and would I be better off rebuilding one or trying to buy a "new" one?