Oil pressure question

[BrentCross]

Hi I’ve got a Lycoming io-540-d4a5 that
Im having oil temperature issue, around 235f so I wanted to see if the oil cooler was clogged. I installed a mechanical gauge in line to the oil cooler and inline from the oil cooler. The reading was around 95psi at idle to the oil cooler and around 90psi from the oil cooler at idle. I know that is very high so I confirmed the oil pressure reading at the oil pressure sender and was seeing 55psi at idle on the mechanical gauge. Question is what could cause this discrepancy? All these were done with cold oil

Thanks

 

[Avanza]

Hi I’ve got a Lycoming io-540-d4a5 that
Im having oil temperature issue, around 235f so I wanted to see if the oil cooler was clogged. I installed a mechanical gauge in line to the oil cooler and inline from the oil cooler. The reading was around 95psi at idle to the oil cooler and around 90psi from the oil cooler at idle. I know that is very high so I confirmed the oil pressure reading at the oil pressure sender and was seeing 55psi at idle on the mechanical gauge. Question is what could cause this discrepancy? All these were done with cold oil

Thanks

there will be different pressures depending on where the gauge is connected in the system.
Close to the oil pump you will
see higher pressure and far away from the pump pressure will be lower.
This is especially true when oil is cold and pressure dropps will be higher.
Your readings could be normal.


Good luck

 

[BrentCross]

there will be different pressures depending on where the gauge is connected in the system.
Close to the oil pump you will
see higher pressure and far away from the pump pressure will be lower.
This is especially true when oil is cold and pressure dropps will be higher.
Your readings could be normal.


Good luck

Thanks for the response…part of me questions the fitting I used to pick up oil pressure from inline the oil cooler lines. I used one of the cheap straight through Chinese fittings with a 1/8” not hole at the midpoint in which the fluid filled mechanical gauge was mounted. Thing is with these cheaper Chinese fitting the inside diameter is smaller then a standard -8 fitting. I’m wondering how much this compression of oil, due to the smaller diameter, would cause the increase in pressure.

Thanks
Brent

 

[Freemasm]

Thanks for the response…part of me questions the fitting I used to pick up oil pressure from inline the oil cooler lines. I used one of the cheap straight through Chinese fittings with a 1/8” not hole at the midpoint in which the fluid filled mechanical gauge was mounted. Thing is with these cheaper Chinese fitting the inside diameter is smaller then a standard -8 fitting. I’m wondering how much this compression of oil, due to the smaller diameter, would cause the increase in pressure.

Thanks
Brent

Would need actual IDs between the two fittings to make a real determination but making assumptions, it's extremely doubtful that this is a main contributor to your observation.

Clogged coolers are very rare. Fouled coolers a little less rare. Vernatherm would be the first guess if this is an emergent issue. Air supply/air management is the best guess if the problem has always been there.

Keep us informed and best of luck.

 

[Southern Pete]

Thanks for the response…part of me questions the fitting I used to pick up oil pressure from inline the oil cooler lines. I used one of the cheap straight through Chinese fittings with a 1/8” not hole at the midpoint in which the fluid filled mechanical gauge was mounted. Thing is with these cheaper Chinese fitting the inside diameter is smaller then a standard -8 fitting. I’m wondering how much this compression of oil, due to the smaller diameter, would cause the increase in pressure.

Thanks
Brent

In general oil is not compressible and there is very little flow into or out of a gauge, it is only measuring pressure. Therefore your fittings are unlikely to have much of an impact. The cooler is quite a labyrinth so some pressure drop would be expected. High oil temps are often caused by lack of airflow through the cowling. As mentioned above, is the oil actually flowing at full rate through the cooler?