Im having an oil pressure issue im hoping someone can shed some light on. This is on a Continental C90- 8 mid time with 25 SMOH cylinders using Aeroshell 100 mineral oil. 75 percent of the time with the oil temp stabilized at 180 degrees I am getting about 39 pounds of oil pressure. About 25 percent of the time with the same oil temp I am getting about 32 to 34 pounds of oil pressure. The change in oil pressure never occurs in flight , only after shutdown and restart. The problem is evident at start up as the pressures are lower across the board from start up, cruise and hot idle. The oil pressure gage is a steam gage and didnt have any indication issues with the last engine that was removed 25 hours ago. The PRV spring is new and there is one washer istalled. Any insight would be greatly appreciated.
Oil pressure issue
- Thread starter kodiakcub
- Start date
cubdriver2
FRIEND
upstate NY
Try bleeding the line at the gauge with the engine running, might be airbound?
If you live in a cold place fill it with Kero or Diesel
Glenn
If you live in a cold place fill it with Kero or Diesel
Glenn
NunavutPA-12
FRIEND
67.8N,115.1W CYCO Canada
In a similar vein, I have chronically high (indicated) oil pressure (90 to 95 PSI). Would the gauge indication change (lower) if I were to fill the line with kerosene/Jet A? Or would it make any difference at all?
The pressure relief valve (old type) is adjusted as far as it can go.
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BC12D-4-85
SPONSOR
Fairbanks, AK.
I had some pressure slow startup and later variability on my C-85 Stroker. The A&P flushed the line with brake cleaner and refilled with M-5606 hydraulic fluid (had a squirt container handy) then bled it a little at the gauge. Lots of built-up oil and carbon crud was flushed out. Seemed ok after.
At the engine or in the gauge could be other issues however.
Gary
At the engine or in the gauge could be other issues however.
Gary
skywagon8a
MEMBER
SE Mass MA6
Nice tight engine. My IO-360 runs at 89-90 all the time in warmer ambient temperatures than yours. Don't be concerned.
Still having this same issue. I was Just wondering how the oil screen bypass works in a C90. Is it possible that I'm bypassing the screen occasionally? Would screened oil have slightly more pressure than oil going thru a bypass valve?
I am only running a oil screen and do not have a filter installed.
BC12D-4-85
SPONSOR
Fairbanks, AK.
The oil pressure relief mechanism is shown in the overhaul manual. Download one and have a look. If mine I'd have it examined for potential sticking of the parts. Also check the pressure screen while you're in that rear area. Clean and fill the oil pressure line to the gauge to make sure it's clean inside.
Gary
Gary
I'll download a copy of the overhaul manual and have a look. I've had the pressure relief valve out when I installed the new spring and everything looked fine with that.
I'm sure it will be in the manual but was wondering how the oil screen bypass works. I have been pulling the screen at every oil change.
Thanks
I'm sure it will be in the manual but was wondering how the oil screen bypass works. I have been pulling the screen at every oil change.
Thanks
BC12D-4-85
SPONSOR
Fairbanks, AK.
I'm not an A&P and certainly no expert, but have been around for part of a few overhauls of small Continentals. As far as I recall and have recently seen in both the overhaul (p. 23; and Fig. 46) and parts manuals (Fig. 11) for the C90-8, the oil screen has no dedicated bypass valve. Instead overall oil gallery pressure is likely regulated via the PRV installed at the rear of the right oil gallery...the pump feeds the left gallery looking forward.
I'd remove the PRV assy and make sure the relief plunger moves smoothly throughout its bore along with the spring. Make sure the plunger and seat area are clean. Maybe others can help more.
Edit: I have heard about the oil pump suction tube not being sealed well by the asbestos gasket at the pump housing. If it gets loose and leaks air in oil pressure may be affected (an assumption). Ad all that assumes the oil pump is intact and not overly worn.
Gary
I'd remove the PRV assy and make sure the relief plunger moves smoothly throughout its bore along with the spring. Make sure the plunger and seat area are clean. Maybe others can help more.
Edit: I have heard about the oil pump suction tube not being sealed well by the asbestos gasket at the pump housing. If it gets loose and leaks air in oil pressure may be affected (an assumption). Ad all that assumes the oil pump is intact and not overly worn.
Gary
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Dan Gervae
FRIEND
Upper Peninsula of Michigan
Oil pressure is within limits for the C90. 30-40psi per the type certificate. Are you just worried about fluctuations?
the oil pressure relief valve in the small continentals, forget about the lycomings, is suppose to start opening at 30-35 psi, thats with a good spring thats in spec with no washers. notice i said start opening. so at 32-34 lbs its right where continental wants it to be. idle minimum per continental is 10 psi. and remember cold oil is thicker and is going to move slower past the relief valve until it warms up.
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your oil pressure is actually perfect, the way continental intended. go to there page 27 and read paragraph 3-42. http://veteranflyg.se/wordpress/wp-...75-C85-C90-O-200-Overhaul-Manual-Aug-2011.pdf
Yes just the fluctuations. If I fly an outbound leg with oil at 180 degrees and 35 psi then I shut down and restart and the return leg the temp will be 180 with 40 psi. This happens occasionally. The oil pressure is always within limits. I don't remember that inconsistent pressure on the last engine but it sounds like that may not be cause for concern.
BC12D-4-85
SPONSOR
Fairbanks, AK.
^^^Kodiak does rpm during flight move the pressure gauge reading?
Gary
Gary
Yes, my example is using the same cruise RPM. If I throttle back the pressure does drop.
BC12D-4-85
SPONSOR
Fairbanks, AK.
Is your tach consistent and accurate?
Gary
Gary
New tack and cable 380 hours ago. Mitchell recording tack but I have not checked it against a hand held tach yet.
Gary, Thanks for bouncing some idea's off me about this oil pressure issue. I may not have a problem but I think ill pull the oil tank and check the gasket on the pickup tube as you suggested. That is one thing that I havnt tried yet and seems like it could possibly cause the issue.
Dan
Dan
BC12D-4-85
SPONSOR
Fairbanks, AK.
Good luck dan with your project. Like many have said your oil pressure is good but parts do wear and engine heat/rpms vary. That pickup tube gasket deal I read about before. The lower the oil in the sump the more likely lifting it can work the pump. Same for oil viscosity and so on. Being mid-time with new cylinders why not look the rest over good so you can get to TBO with peace of mind? You could also check the sump oil temp on landing with a therm to make sure your temp gauge is close. Let us know what you discover.
When idling ready to shut down after a run what's the oil pressure? Does it stay about the same run to run?
Gary
When idling ready to shut down after a run what's the oil pressure? Does it stay about the same run to run?
Gary
BC12D-4-85
SPONSOR
Fairbanks, AK.
20's good at idle when hot in my experience. Keep logbook notes of that sort of stuff over time in case it suddenly changes.
Gary
Gary
Lots of good info on the old Sac Sky Ranch site.
https://web.archive.org/web/20111225183936/http://www.sacskyranch.com/eng26.htm
Sent from my iPhone using SuperCub.Org
https://web.archive.org/web/20111225183936/http://www.sacskyranch.com/eng26.htm
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Steve Pierce
BENEFACTOR
Graham, TX
I suspect something under the pressure relief ball, intermittent gauge or trash being sucked up intermittently by the oil suction tube. I would start with the easy stuff first.
cubdriver2
FRIEND
upstate NY
You can bend a 1/4" 90 on a welding rod and reach up thru the drain hole in the sump and hook the pickup tube and see if it wiggles
Glenn
Glenn
