Oil Pressure Issue

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4 months 2 weeks ago #3303 by STEVE ELLS
Replied by STEVE ELLS on topic Oil Pressure Issue
Hi Gary;

The Continental (as well as the Lycoming) oil pressure relief valves and relief valve components are very simple. Spring pressure is applied to a plunger in the case of the Continental and a round ball in the case of the Lycoming. The spring pressure holds the plunger/ball against a seat.
When the plunger/ball is against the seat all the pressure produced by the pump is in a closed loop system.
When the OP (at normal operating temperature) is high enough to push the plunger/ball off the seat by overcoming the spring pressure the loop opens so that "excess" pressure is vented to the crankcase oil sump.
I too had a low OP problem in the Lycoming engine in my Comanche recently. After cleaning the seat and ball my OP is back where I'm used to seeing it in cruise. (77psi)
I never used to look at my OP during take off--why would I? I guess I thought that since it was "in the green" during run up I was OK. This practice was reinforced by seeing it where I'm used to seeing it in cruise. The redline OP in my Lyc is 110 psi. I now notice that it gets up to 90 psi during my first takeoff of the day.
It doesn't sound like you have a problem that warrants further effort.
I'm sorry I didn't get back to you sooner.

Best,
Steve

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4 months 3 weeks ago #3297 by Gary Shaffer
Replied by Gary Shaffer on topic Oil Pressure Issue
Then there's the question of the exact part # of the oil pressure plunger. The attached photo with two plungers shows the one inserted last year on the right. It's taller and has a hole drilled in the shaft. I ordered a replacement, assuming that that might be the problem, and got the one on the left, also shown in the single-plunger photo. It's marked with the right part number, but looks noticeably different. The A&P didn't want to put the shorter one in, since it's so different.

I knew that aircraft maintenance would be expensive, but I never imagined that it would be so overwhelmingly frustrating.

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4 months 3 weeks ago #3296 by Gary Shaffer
Replied by Gary Shaffer on topic Oil Pressure Issue
And the saga continues: Finally got a chance to fly it last Friday. On startup, the OP worked up to 64 over about 30 seconds. I let it warm to 95F before doing the runup, and saw 74. On takeoff, it hit 81, then slowly dropped to 55 as the OT climbed to 180. The POH lists max OP as 100, so technically it's OK, but after seeing it between 30 and 60 for the last decade or so, 81 worries me a bit. Is it worth going in and backing out the OP relief valve a little? I have an EI electronic OT/OP gauge, but there's also the original direct-reading gauge, and I don't want hot oil spraying around the cabin at 80 PSI!

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5 months 5 days ago #3272 by STEVE ELLS
Replied by STEVE ELLS on topic Oil Pressure Issue
Yes, that Continental washer (631653) is expensive. I'm glad you again have good OP. I hope he didn't charge you for opening the valve back up and installing the washer.

Since he has been the only one in there

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5 months 5 days ago #3271 by Gary Shaffer
Replied by Gary Shaffer on topic Oil Pressure Issue
Passed it on. He now says that there was a special, $32 washer that was missing. He replaced it and it now shows 54 PSI immediately upon startup. He's the only one who has worked on that area in at least 5 years.
Thanks again!

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5 months 6 days ago #3270 by Gary Shaffer
Replied by Gary Shaffer on topic Oil Pressure Issue
Thanks; I'll pass that on.

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