View Full Version : The Manifold Pressure Guage

10-11-2016, 08:58 AM
1957 Tripacer. It has a manifold pressure guage,
probably original to the plane, not sure why, but
it's alive. Maybe I should get used to it against the day I get a complex aircraft. Only problem:
It has become the repository for what look like bug cocoons. So. Can I legally unscrew the panel cover, and try to open the face of the M.P.G. to clear them out? They really BUG (sorry!) me. Thanks!

Fred Mayes
10-11-2016, 04:00 PM
Hi Soquetero
Years ago some pilot added a manifold pressure gage and some installed a constant speed propeller which requires a m.p. gage. I don't know about the bugs.

Fred Mayes
Pacer N7478K

Tom Anderson
10-14-2016, 07:16 PM
I don't have a gauge sitting in front of me to tell you exactly how to take it apart, but the gauge uses a bellows inside to move the needle and thus on this instrument the case is not sealed. It should not be difficult to remove the cover and clean it. The escutcheon covering the panel comes off very easily. Hopefully you can pull the glass cover of the instrument off without taking the instrument out. You should not have to seal it when you put it back on. Officially this should be done by a mechanic, but since the manifold gauge is not a required instrument, I would just go ahead and do it.

Tom Anderson

01-29-2017, 02:27 AM
Dennis Here! Good news (sort of). It WARN"T bugs in the manifold pressure gauge! It is the deteriorating gasket (too large to be called an o-ring) decades old. A&P/AI removed the gauge, line, & fittings, plugged the cylinder connection port. I'm still saying the gauge came from the factory: No documentation adding it, AND, it's tagged with a Lockhaven PA Instrument Company, dated 12/10/1956 (plane's a '57). I'm going to send it to be overhauled, and then I'll probably have it put back in because it DID come with the aircraft. A&P/AI said I was probably losing "some compression" on the connected cylinder because of the leaking instrument. I wonder if that's where my 132 mph cruise has been going... we'll find out tomorrow!

Fred Mayes
01-29-2017, 11:40 AM
soquetero, I think you may be right about the original equipment. I remember a new Tri-Pacer with a manifold pressure gage from the factory, and a constant speed Prop.