Bouncing oil pressure gauge needle

[PlaneDoctor]

I know that someone has had this problem before, but I can't remember the cure. I have a customer with a 150 HP -18 that the oil pressure needle bounces all over the place. The -18 was rebuilt 3 years ago, and a new oil pressure/temp gauge was installed at that time. The oil pressure line to the gauge was replaced with a one piece line fabricated from -4 303 Aeroquip hose with 491 hose fittings. We also installed a restrictor fitting in the case. I have bled the system at the gauge, but the needle still bounces. Any suggestions?


Thank-you,

Tom.

 

[Wingman1]

Might want to check the oil bypass/pressure regulator ball and spring assembly.

 

[Toothcarpenter]

I changed the spring and ball in the pressure relief valve. That solved the. Problem. I also welded t he fitting closed at the engine and drilled a tiny hole in it. After several experiments, it was obvious that the restrictor orifice could be very small. That would slow the pumping out of the oil if a line failure occurred. When I was struggling with the same problem there were a number of helpful responses. Search for fluttering oil pressure, or fluctuating oil pressure. Cleaning the pressure relief valve, along with a new spring and ball solved it for me. Several people talked. Of particles holding the ball and seat slightly open. I Never found anything in the seat.

 

[PlaneDoctor]

Thanks guys, I will give it a shot.

 

[Steve Pierce]

Look at btracy's post in this thread. http://www.supercub.org/forum/showt...Oil-Pressure-Relief-Valve-Looks-like-Location

 

[jbird121.5]

You need to get all of the oil out of the line. Air in the line acts as a cushion, it will compress to absorb the pulses of the pump. The oil will not compress, and you get all of the pulses of the pump. This is the same in any pressure gauge. Oil pressure,fuel pressure,torque gauge on a PT6,etc. [Manual guages]