Engine guru help needed - low oil pressure

[markscogg]

Since my 'annual' last month, my oil pressure is lower on the second flight of the day.
Was always 80 cold and 70 hot at cruise. Idle 45 hot.
Now ONLY on the second flight of the day it is down to 60 hot.
Have seen some tiny bubbles in the oil on the dipstick.
We had both screens out of the engine at the annual. Could that have anything to do with it?
Today I took off the pressure relief valve. Five washers already in it, but they were 7/16 O.D. and dropped into a recess in the bottom of the pressure relief valve. I added three more, to actually put more pressure on the spring.
What is next?

PS, spring is not painted, .055 dia wire, so it must be a 9# p/n 61084
Should the washers be 1/2 O.D. or 7/16 O.D.?
O320-D2J engine.
Thanks

[Low Pass]

First, it sounds like you're making this too complicated - at least at this stage of the game. What did you change (touch) during the annual? You change oil spec/type? You change or disconnect any hoses? You change filter type/make? Remember basic troubleshooting. Something changed to give a changed indication. Investigate what you changed or touched first. Don't add variables tampering with things you didn't change! The odds of some untouched item failing coincidentally are lower than the odds of you not putting something back together right.

You said screens (as in more than one)? I'm only familiar with one in the bottom of the sump. Where's the second? I'd go back and make sure you reinstalled the screens properly first of all. It's a bit of a trick to get the sump screen back in right if you've never done it before.

[cajunwings]

Mark: Has the idle oil pressure changed from what it was before? What type of indication system do you have? A known good mechanical gauge "Teed" into the system can rule out indication problems. Don B

[markscogg]

Originally Posted by Low Pass

First, it sounds like you're making this too complicated - at least at this stage of the game. What did you change (touch) during the annual? You change oil spec/type? You change or disconnect any hoses? You change filter type/make? Remember basic troubleshooting. Something changed to give a changed indication. Investigate what you changed or touched first. Don't add variables tampering with things you didn't change! The odds of some untouched item failing coincidentally are lower than the odds of you not putting something back together right.

You said screens (as in more than one)? I'm only familiar with one in the bottom of the sump. Where's the second? I'd go back and make sure you reinstalled the screens properly first of all. It's a bit of a trick to get the sump screen back in right if you've never done it before.

I have 2 screens, with no oil filter. A&P took out the one in the sump, I never touched that one. I always clean the one where the oil filter would normally be during oil changes. Can you put the sump screen in wrong?

[markscogg]

Originally Posted by cajunwings

Mark: Has the idle oil pressure changed from what it was before? What type of indication system do you have? A known good mechanical gauge "Teed" into the system can rule out indication problems. Don B

Idle pressure still 45 hot. Westach analog gauge. The 4 gauge combo in one 3 1/8 instrument. Small hose goes to a sending unit on engine side of firewall.

[Bavafa]

I am not a guru mechanic but I don't think it is your bottom screen. There is no left or right/ up or down on that screen. It is recommended to change the crush washer though which still would not have any thing to do with the oil pressure.

But the outside temp when it could have much to do with it. Lets say if you always checked the cold pressure when the temp was around 40 F and now you are checking it when it is 70F, then you will see a lower pressure because the oil in the engine is not as cold. The same is true for your hot temp. An engine with the oil temp at 200 will have a lower pressure then for the same engine at 160F.
Also don't forget the quantity of the oil will affect your oil temp. The more oil you have the cooler it will run.

[markscogg]

Originally Posted by Bavafa

I am not a guru mechanic but I don't think it is your bottom screen. There is no left or right/ up or down on that screen. It is recommended to change the crush washer though which still would not have any thing to do with the oil pressure.

But the outside temp when it could have much to do with it. Lets say if you always checked the cold pressure when the temp was around 40 F and now you are checking it when it is 70F, then you will see a lower pressure because the oil in the engine is not as cold. The same is true for your hot temp. An engine with the oil temp at 200 will have a lower pressure then for the same engine at 160F.
Also don't forget the quantity of the oil will affect your oil temp. The more oil you have the cooler it will run.

Outside temps are cool here in North Carolina - about 55 at the surface when flying today. Oil temp got up to 170 max on first flight of the day. Never got above 160 on second flight, though it was a longer flight. So the oil temp was slightly LESS when the pressure was lower.

[markscogg]

Can the sump screen be installed wrong? Can it cause low oil pressure or the tiny bubbles in the oil on the dipstick?

[Low Pass]

Originally Posted by markscogg

Can the sump screen be installed wrong? Can it cause low oil pressure or the tiny bubbles in the oil on the dipstick?

Sure. If you don't get it seated properly, you'll crush it. Will it cause bubbles or a pressure reduction? I doubt it, but you need to look at what changed first. The screen was removed. It would be on the top of my list.

As for the outside air temp being a factor, it would have some effect. But it would really suprise me that it would make a 10 psi difference. But talking out of the other side of my mouth, you need to know the temps from before and compare to the after.

Stupid question - you sure you have enough oil in the system??