As I said in an earlier post, my vacuum pump failed about 1 hour from my home destination after delivering about 2 years and 150 hours of service.  This pump had a blast air shroud around it, but was present thru a prop strike about 120 hours before its' demise.

 

The shaft sheared in the proper shaft shear location.  However, there was no damage to the pump chamber.  This was a good thing since no particles were drawn back into the gyros.  I do not know why the shaft sheared in cruise flight.

 

In testing the new pump I did notice that is was delivering 5" during idle engine operation. The failed pump had fallen to 2-3 inches during idle for at least the last 40-50 hours. 

 

The next time a vacuum pump fails to hold the proper vacuum at 900-1000 rpm, it will be cause for me to investigate further.  That is if I don't switch to an all electric system before that happens.