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Lycoming IO-540 Oil Pressure Question

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HomeBuilt101

Well-Known Member
Joined
Oct 20, 2015
Messages
384
Location
Aguila AZ
I have been trying to troubleshoot a low oil pressure issue. For the Lyco-Saurus IO-540 drivers out there, CAN YOU PLEASE HELP and provide me with what is your "usual" oil pressure for the following parameters?

Idle at 1000 RPM engine cold (like 50-70F oil temp)

Idle at 1000 RPM engine cold-ish (like 120F oil temp)

Takeoff rpm with oil temp cool-ish (Like 150F)

Cruise RPM 2500 with oil temp at 180-200F (2300 RPM)

After landing idle 1000 RPM with engine and oil all warmed up

Also, how far in has your oil pressure regulator been turned in (1/4 threaded in/ 1/2 threaded in / all the way threaded in)?

RUNUP WITH OIL COOLER DISCONNECTED:


RPM/ OIL TEMP/ OIL PRESSURE


1000 / 76/ 83


1700 / 91/ 90


MAX POWER / 104 / 85


2500/ 137/ 62


2500/ 152/ 54


MAX POWER/ 155/ 58


2500/ 172/ 57


1000/ 170/ 26 ONLY 1 PSI OVER MINIMUM LIMIT


The engine has only 170 hours since major overhaul. It has an oil fed and regulated turbocharger system from a 1970 vintage Cessna 210.

Thinking it was an oil pressure regulator problem...I removed the adjustable regulator from the engine case and inspected the ball, spring, and seat and all were clean and no apparent damage (I assume the spring is the right one)

Thinking it was an abnormal wear problem... I drained the oil into a clean bucket through a funnel that has a fine mesh screen and the screen was absolutely clean and the bottom of the bucket was also clear. I removed the oil suction screen from the engine and it was also completely clean and in excellent shape. I also removed the oil filter and cut it open and it was completely clean…not even a spec of material.

Thinking it was an oil viscosity problem...I re-serviced the engine with 10 new quarts of 100W Plus and did another runup and the cruise power oil pressure was fine however the hot idle oil pressure was back down at 27 PSI…

Thinking it was the oil cooler reducing flow problem...I disconnected the two oil cooler hoses and blew them out with compressed air and the oil came out clean and when the hoses were empty it seemed that the air blew through easily (some resistance but not unexpected). So I bypassed the oil cooler completely with a short piece of oil line and did a runup and sadly determined that the oil cooler and associated hoses are NOT the culprit.

As before with fresh oil, the oil pressure with cool oil went up to normal and then as the oil heated up the oil pressure dropped down to low limits.

Does anybody have any suggestions???

-Can the Vernatherm be dumping oil pressure?

-Can the turbocharger oil system have some kind of check valve that is bypassing? The system has a hose from the cool side of the oil cooler port on the engine to the hose to the bottom of the turbocharger bearing and then above the turbocharger bearing is a Commercial Aircraft Products Valve Check Part Number: 340100. This is supposed to prevent oil from dripping back down into the turbocharger when the engine is not running.

ANY HELP...PLEASE!?!?!?!?!?!?!?!?!?!
 
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