I was out cruising with a friend when he had an in flight problem on a 2 mile approach. He heard what might have been a metal to metal squeal and his oil pressure dropped to 15 psi and started to bounce between 20-35 psi. I ask if there were any other gauges that were out of line and did his engine change in any way (i.e. noise or rpm)? The answer was no to both. Landed without any issues. I told him that 98% of the time it is a bad sender when it acts this way. If the pressure goes real high (100 psi) then it is usually a ground. If it fluctuates all over it is a bad sender or bad wire connection. If it just drops way down low it is usually the sender. So the next morning we took a look at the engine. I told him we needed to make a diagnosis based on some facts and not just hunt and peck around. It was time to break out the oil pressure test setup that cost about $20 to make. It all comes from any hardware store. Here are some pictures and a video to look at. I apologize up front for the poor video quality as it was a spur of the moment thought. I'll do it again one day for a better quality sequel. It is just 1/8" copper tubbing, a brass tee, 4 x 1/8 NPT-27 thread compression fittings and a 100 psi gauge. Pull the oil pressure sender out. Screw in a brass fitting and run it out about 18" and place the tee in line. then run the rest of the tubing and gauge into the cockpit. Screw the oil pressure sender in the top of the tee and connect the oil pressure sending wire. The gauge will be grounded through the copper tube. Start the engine, loosen the fitting by the gauge and let a few drops of oil come out to purge any air. Now you can compare the engine's actual oil pressure to the instrument panel reading.

p.s.the metal to metal squeal was actually the low oil pressure alarm. The problem was just a bad oil pressure sender.


Picture of a smiling happy friend attached
oilpressuretestgauge.jpg (You do not have access to download this file.)
oilpressuretestsetup.jpg (You do not have access to download this file.)
oilpressuretestteefittingwithsender.jpg (You do not have access to download this file.)
oiltestfittinginoilpressureport1.jpg (You do not have access to download this file.)
oiltestfittinginoilpressuresendingport.jpg (You do not have access to download this file.)
LokiFace.jpg (You do not have access to download this file.)

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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