OK, we now know the problem was a pinched hose, but there is some
speculation that a failed vacuum pump can actually blow dust backwards into
the vacuum instruments. The idea is that residual vacuum at the instruments
allows the higher pressure at the failed pump to push the dust into the
vacuum instruments. There is an STCd filter that can be placed between the
instruments and the pump designed to prevent dust backflow if the pump
fails.

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

Time flies like an arrow, fruit flies like a banana.

"Morgans" wrote in message
...

"Dan Luke" wrote

Or the pump is shedding carbon and fouling the system?

Only if it is a pressure system, instead of a true vacuum system.

Instruments run off of vacuum so that any carbon or other debris from a
failed pump goes into the pump and out the exhaust, instead of into the
instruments or plumbing.

But you knew that and had a brain fart, right? g