Is there anyone who sell new ones for a twin Comanche. This particular gauge has he 2 red buttons that suck in or stay out if there is no vacuum. Thanks George

What mine is doing on the right engine is at 500 /600 or so rpm the right little red button is hammering the glass. If you throttle up the engine just a little it stops. other than that the suction is good.

You might have a leak in a hose... in the right side.. JMHO
Jim

 

We had a few problems and finally ended up replacing every hose - instrument through firewall to check valve, check valve all the way to the pumps. check valve has been OH by rapco and pumps are new - should be good for another 40 years.

You most likely have a vacuum pump that is on the weak side. Vacuum pumps pump in pulses even though it is a rotary vane, and each pulse at lower pressures may be seen in the buttons (RPMs in the 5-600 range will not make much vacuum). If the buttons are pulled out of view solidly by 1000 RPM, and they operate independently, ie the right engine doesnt pull both buttons in, then you have a normally operating vacuum system. IF you wish to chase the issue further, replacing the vacuum pump most likely will solve the issues.
-Zach

 

 

George, Your right vacuum pump is calling.
Steen

 

 

That looks good... not sure if they picked up the PH pumps or not... after the Senator in MO was killed... they may have sold their line and I don't recognize the other vendors in the Aircraft Spruce catalog.
Jim

IIRC a contributing factor to the MO Senator accident was the Twin's check valve was not working and for Part 135 operator's that is now an AD every so many hours to either check or replace. Heard about this after a double vacuum pump failures due to bad engine hang by Altus (no longer in business). I started watching this on engine start and shut-down, sure enough 4 years later, the check valve went. O/H by Rapco and runs well now. The removal highlighted the bad hoses ... suspect this contributed to a mysterious double vacuum pump failure even Rapco expert could not explain (in warranty). Every single 'rubber' hose has been replaced from engine through fire wall in the nose and behind the panel to each instrument. Amazing what inventive charlie-romeo-alpha-pappa hoses had been installed behind the panel to instruments. Thanks to Clifton, I'm highly confident the instrument to vacuum pump system will long outlast me.

Pat... don't be comparing your anticipated life span to that of a mechanical vacuum pump... I'm betting on you girl!

Jim

Thanks Jim!

Al Powers is my current inspiration. At age 80 he OH'd both engines. He and the engines are running great.

I went with the Rapco pump, changed out the Garlock seal used a new gasket and the pump leaked on test run up. I took the pump off used a new gasket checked the Garlock seal again tightened down the pump, leaked on test run up again.

What is that small oil passage on the right bottom of the mounting flange? I can't understand where the oil is coming from. I know the gasket I took off had only the 4 mounting holes and the new gasket has many small holes besides the 4 mounting holes.
Thanks George