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?

 

Next to finding out an Oil Cooler Hose leaked all the Oil out of the Engine while you were driving a Vacuum Pump Failure where parts break is next on the list of things likely to damage your Engine.

Your biggest worry may not be the Vacuum Pump.

This is not the only way it can happen but the Older Vacuum Pumps had a Bearing that the Bearing Cage can come apart on and the ***** fall out. After that the Arm Mechanism rides on the Timer Cam and eventually destroys the Arm Mechanism and even the Timer.
If your lucky that is all that happens.

Often the parts of the disintegrating Vacuum Pump Parts fall into the Timing Chain and Gears causing Valves to and Pistons to collide damage the Engine. Especially the Valves, Camshaft and or the Camshaft Bearing Towers.
Remove the Valve Cover and inspect those items.

Remove the Vacuum Pump and inspect the Timer for wear and end play.

Do not crank the Engine with the Starter but turn the Engine by hand several complete revolutions and see if it hangs up on anything. Removing the Glow Plugs allows the Engine to turn easier.

I don't know about the earlier Models but on the later Models with the Piston type Vacuum Pump if the Timer Bushing is worn out and the Timer has too much in and out play it can ruin a new Vacuum Pump.

You need a Good Vacuum Pump Housing in order to rebuild it and yours is cracked. Also the cost of the parts to do a complete rebuild on a Vacuum Pump has risen to the extent that you are better off with a new Vacuum Pump and the Warranty that comes with a new one.