Vacuum pump problem, PA-30

[Frank]

Can someone describe how the check valves are set up in the vacuum system on a PA-30? Where are they (or is it one unit?)

The first time I saw a problem, I started the left engine first, no problem; then the right, and a loud buzz started immediately, which was shortly identified as the right vacuum button vibrating in and out very fast. I shut down, called in a mechanic to observe the symptoms, started the same sequence again, and everything was perfect. The problem went away, not to reappear for several hours.

Now if I start my right engine (only), I get no red button on the vacuum gauge (indicating that the left vacuum isn't operating), and low vacuum indication (< 1"). After a minute or two, or if I increase RPM to the low teens, the red inop button for the left side pops out, but I also get a buzz (not nearly as loud as that first time), which seems to be coming from the vacuum gage.

Maybe I've got a bad vacuum pump, but it seems to me the check valve(s) may be faulty. Any thoughts?

[Zach Grant L1011jock]

Frank,
Not really sure if I totally understand your post but you certainly could have a bad check valve manifold. It is located under the nose boot cowl, on the forward side of the forward cabin bulkhead. It looks like a tube with two riveted pipe flange type joints, and 4 hoses exiting it. It is still a redly available part.

-Zach

[Frank]

Thanks, Zach... I'll take a look at that.

[Kristin Winter]

[TurboPA30]