Vacum pump seal
 

I'm having trouble with the seal between the vacum pump and power steering pump, have replaced it twice and today it went out again.
The seal is perfect it just blows out of the housing that you press it into, when you pull the power steering pump off the seal falls out with it. I've been a mechanic fot 40 years and haven't run into anything like this.
Any suggestions appreciated.

Is the oil drain blocked in the vacuum pump? Cant think how or why the seal would get pushed out.

It doesn't appear to be. The seal seems to press in very easily, the seal kit I got was FelPro, have one ordered with Cummins brand name to see if there is any difference.