Oil Pressure Issue

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5 months 6 days ago #3269 by STEVE ELLS
Replied by STEVE ELLS on topic Oil Pressure Issue
Gary,
Your mechanic needs to pull the oil pressure relief valve assy and re install it.

If after maintenance, the system that was worked on doesn't work as it did prior to the work, the failure is in the maintenance process, or contamination during the service.

The chance of a broken tooth of an oil pump is so slight as to be unmeasurable.

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5 months 1 week ago #3268 by Gary Shaffer
Replied by Gary Shaffer on topic Oil Pressure Issue
Steve,
Well, things went from tolerable to AOG. During the annual, I asked the IA to double-check the OP relief plunger and area for contamination as suggested. He did so, but didn't find any problems, so he reassembled it. We finished the annual, got everything buttoned up, went to start it, and the OP maxed out at 11 PSI on the EI OP/OT gauge. Normally it would be 50+. I shut it down, talked with the IA, he asked me to try again and check the old mechanical gauge. I did so, and saw 0 on both gauges, so I shut it down. No sign of oil leakage. The IA has no idea what the problem is. He's sure that he did the relief plunger work okay, and is speculating that the oil pump broke a tooth or something. Seems unlikely that such a thing would just happen to occur right after working on the relief valve. Any suggestions?
Thanks,
Gary

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1 year 4 months ago #2748 by STEVE ELLS
Replied by STEVE ELLS on topic Oil Pressure Issue
Gary,

I can't tell if you're saying that the OT s get too high half the year, or they don't get high enough half the year.

Modern aircraft oils are able to handle very high temps so I think you're talking about low OTs.

If low OT are a problem, you'll need to find some winter fronts, which should block off part of your oil cooler, or fabricate that you can install to partially block off the oil cooler during cold WX months.

The problem is that Cessna winter fronts for older airplanes are very scarce, So owners improvise.

During the years I spent in Alaska, many owners had a roll of stainless steel self sticking tape they used to temporarily block off enough of the cooler to maintain desired OTs.

You can get a roll of the stuff at a good auto parts store or auto body supply store. It may be aluminum but I think it's thin stainless.

Best,
Steve

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1 year 4 months ago #2747 by Gary Shaffer
Replied by Gary Shaffer on topic Oil Pressure Issue
Steve, thanks for the info. I've talked with my IA and he agrees that since we were seeing higher pressures before the spring replacement, the OP relief valve should be tightened a bit. Also, I need the engine to work at OTs above 180 or the plane is useless to me half the year.

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1 year 4 months ago #2746 by STEVE ELLS
Replied by STEVE ELLS on topic Oil Pressure Issue
The type certificate data sheet (TCDS) for your O-470L cites 10 psi as minimum idling oil pressure and normal operating oil pressure as between 30 and 60 psi.

This specification is correct is the oil pressure is tapped on the 2-4-6 cylinder side of the engine. That's the pilot's side of the engine and as I remember, that's where Cessna installed the oil pressure tap for taking the OP.

I suggest that if your OP is 30 in cruise when the engine is hot, you're OK. And if your hot idle OP is above 10 psi, you're OK.

When an engine has a lot of serious internal wear, it won't be able to maintain the hot idling OP. To me that's the most important OP tell tale.

Happy Flying,
Steve

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1 year 4 months ago #2742 by Gary Shaffer
Replied by Gary Shaffer on topic Oil Pressure Issue
Follow-up: Have had more opportunity to fly lately, and with heavier loads. OP is fine initially, but slowly goes down. By the time the temp gets to 180, it's sitting at 30 PSI at 2450 RPM. Talked with A&P; he agrees that the OP relief valve needs to be adjusted. Will advise results when that happens.

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