Admin2 Posted August 31, 2011 Report Share Posted August 31, 2011 I was out cruising with a friend. ( black and smiling, pictured below) when he had in 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 barked if there were any other gauges 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 I got a step stool since I'm only 24" tall and took a look at the engine. Being short is a problem at times, but all the teeth make up for it. 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 (or 40 bones) to make. It all comes from Ace Aviation .Here are some pictures and a video to look at. It is just 1/8" copper tubbing, a brass tee, 4 1/8 NPT -27 thread compression fittings and a 100 psi gauge. Since most of you don't understand Dog I had a friend work the camera, plus it's that darn height thing again.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. Sorry for the poor video quality it was a last minute thought. 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. Link to comment Share on other sites More sharing options...
Tom Baker Posted September 1, 2011 Report Share Posted September 1, 2011 When I have a failure I test the sender on the bench. A 1/8"to 1/4" pipe bushing and an air fitting plugged into a compression tester. You can take it all the way from 0 to 100 PSI. I have found bad spots in the normal operating range before. Tom Link to comment Share on other sites More sharing options...
Roger Lee Posted September 1, 2011 Report Share Posted September 1, 2011 These senders going bad too often is what prompted Rotax to go to Honeywell and a completely new type of sender. Link to comment Share on other sites More sharing options...
Runtoeat Posted September 1, 2011 Report Share Posted September 1, 2011 Roger, it sounds like the oil pressure senders are going to the dogs. Link to comment Share on other sites More sharing options...
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