Drop in Oil pressure

rvbuilder1 · #1 10-19-2013, 06:49 AM

I have an RV4 with a rebuilt Lyc 0290D with 101 hrs since rebuild.
During a short hop the other day I noticed some differences in oil pressure readings from the last 100 hrs
On starting it usually goes to close to 100psi with cold oil even in the summer then drops to 85-90 when hot and pretty much stays there. On the ground at low throttle it is around 50.
On this flight upon starting it only went to 90psi. In the air it stayed at 85-90 at 2400 rpm. On the ground it was reading 45-50psi.
I have been going to chnge springs or pull washers to lower it to 85-90psi on start which is the spec for the Lyc 0290D and was surprised at the 10psi drop at starting without any changes to the oil pressure mechanism
The oil pressure is taken off the back of the engine and I have read that that is always lower pressure than if you take it off the front of the engine

SHOULD I BE WORRIED?

Walt · #2 10-19-2013, 07:06 AM

Decreasing oil pressure can be indicative of pending internal engine problems. It "could" be indication but don't assume that. The first thing I would do would be pull the oil filter and strainer and check them for metal.

RV8Squaz · #3 10-19-2013, 07:23 AM

Over the years I have often found the "indication" to be the culprit. Before I start any significant maintenance I make sure the gauge or instrument is not lying to me first. On that note, pulling the oil filter is easy. I would do that first like Walt said since it is easy to do. After that check the gauge and sender. How is the oil temp? Temp and pressure go hand in hand.

Jerry Esquenazi
RV-8 N84JE

Low Pass · #4 10-19-2013, 07:51 AM

Quote:

Originally Posted by RV8Squaz

Over the years I have often found the "indication" to be the culprit. Before I start any significant maintenance I make sure the gauge or instrument is not lying to me first. On that note, pulling the oil filter is easy. I would do that first like Walt said since it is easy to do. After that check the gauge and sender. How is the oil temp? Temp and pressure go hand in hand.

Jerry Esquenazi
RV-8 N84JE

Second this. Be 100% sure your pressure and temp indication are accurate before taking anything apart.

rvbuilder1 · #5 10-19-2013, 08:21 AM

Oil Temp has always been good at 175-180 F was at 180 F on this flight.
About time for an oil change anyway it's at 23 hrs. No Filter, just a screen but pulling screen and bottom plug with filtering of oil through cheese cloth should show something if anything is there.

Ironflight · #6 10-19-2013, 08:47 AM

electronic or mechanical gauges? I have replaced several inexpensive oil pressure transducers over the years on various airplanes.

First rule in aerospace is that the instrumentation is more likely to be the fault - so check it first.

rvbuilder1 · #7 10-19-2013, 03:38 PM

How would you go about checking the accuracy of the gauge and sender of a pressure gauge other than taking it to a shop.
In the past I have checked Temp gauges by removing it and placing it in water that is heated on a stove to increasing temps while measuring the water temp with a Thermometer. Is there a more precise method anyone is using
Can you check the pressure gauge in a similiar manner using some type of pressure device? I thought of using air pressure but I believe hydraulic and air pressure measuring mechanism in the gauges are different and don't want to damage the gauge.

BillL · #8 10-19-2013, 04:38 PM

For a static oil or air pressure won't harm either. If it is a resistive transducer, then static pressure vs resistance is the thing to check. But like Paul said, the engine is typically much more reliable than the sensing pieces. It is an easy removal to take it off and check it. Maybe just a loose wire? Corroded connector?

I just happen to have a 10" diameter precision pressure gage that I use as my absolute standard. I found it surplus and took it to work to have it checked.

Jesse · #9 10-19-2013, 05:05 PM

Quote:

Originally Posted by RV8Squaz

Over the years I have often found the "indication" to be the culprit. Before I start any significant maintenance I make sure the gauge or instrument is not lying to me first. On that note, pulling the oil filter is easy. I would do that first like Walt said since it is easy to do. After that check the gauge and sender. How is the oil temp? Temp and pressure go hand in hand.

Jerry Esquenazi
RV-8 N84JE

+1 on this. Those numbers certainly aren't alarming, so if you don't see anything to cause worry, just watch for a trend over time.