> Note to Bill Harrelson - I know you backed up the pump, in 12 years of
> personal experience, I have had no pump failures, but 2 instrument
failures.
> BTW, I also run a cooling shroud on the pump body.


Scott, good idea to keep the pump cool.
I know that vacuum pumps fail. I know this because I keep reading it here on
the list. I have been extremely lucky, however. In 25,000 hours, much of it
in general aviation airplanes including many years as a flight school owner
and examiner, I've never had a pump fail on a plane I was flying or on one
that I owned in the flight school.  This equates to something like zero
failures in 100,000 hours. I have, however, had many alternator failures.
Maybe the key to long pump life is to beat them up with rental/flight
instruction use. I too have had a few gyro instrument failures, including
some in airliners (electric, $50,000 units).

Bill
harrelson@erols.com
N5ZQ