Oil Pressure question

[alwaysoar]

Re: Oil Pressure question

Frank, I have one I took out of my plane. It comes up slow, then jumps up to normal readings. If you want it I'll give it to you for the cost of shipping.
Ed

[Hank Jarrett]

Re: Oil Pressure question

Before you spend a lot of money get a little messy. Unhook the line from the indicator and the engine and flush it out with light oil. When I rebuilt my panel I was surprised at the sludgy gunk in the old line. (Looked like it hadn't been looked at since 1941) When instruments are overhauled or replaced sometimes the lines don't get cleaned.
Hank

[Frank DeBartolo]

Re: Oil Pressure question

Update on the oil pressure problems.

On cold start, the gage reads zero for appx 10-20 seconds then comes up to 31 psi and stays at 31 during idle, taxi, takeoff, climb and cruise. Today OAT at altitude was right at 50F and the oil temp gage warmed up to 150F and stayed at 150F and appx 31 psi throughout the flight. I flew appx 1 hour today and after landing and refueling at restart, the oil pressure gage reads zero for appx 20 seconds then goes slowly up to appx 20 psi during taxi. In front of the hangar I did a static Runup (appx 2000 RPM) and the gage read appx 25-26 psi. (I did not do and probably should have done takeoff climb cruise and landing to see how the gage reads after refueling when the engine is hot to see if the gage would go higher than 25 or 26 psi). My IA and I think it is probably a bad gage but I am looking for other opinions on this just to make sure we are on the right track. I tried giving my gage the big tapping finger (are you out there Stormin)---to get the pressure up but this trick only worked once (and it may have been that after 20 seconds the finger tap and oil pressure coincided.

Thanks,

Frank
N43684

[alwaysoar]

Re: Oil Pressure question

Frank, Have you bled the line, and you're welcome to try out the one I offered you a while back. They're easy to install.

Ed@BTV VT
TF 527

[Frank DeBartolo]

Re: Oil Pressure question

Ed,

Thanks for the reply. I have not bled the line and I still have the old oil pressure gage that originally came in the plane. The IA I am working with has a gage as well. Thanks for the offer. Probably the best thing to do is bleed the line first.

Thanks

Frank

[alwaysoar]

Re: Oil Pressure question

The rule of thumb is oil pressure should start to register within 30 seconds; yours does. If you pull your prop thru 8-10 times before you start up, pressure might come up quicker. 30-40 psi is normal operating range, so running 31psi is ok. And oil pressure can be adjusted down or up. Your IA should know how to do that.

[Frank DeBartolo]

Re: Oil Pressure question

Ed,

The thing about this that bothers me is that after flying and refueling, I have someone prop me and the engine is still hot because I landed appx 10-15 minutes before. It takes appx 20 seconds for the oil pressure to come up--should it take that long with a hot engine. After restarting the hot engine it reads 20 psi at idle. This was last nite. I did a static runup in front of my hangar at 2000 rpm and got appx 25 psi at static. Why doesn't the pressure come up to 30 psi at static. On initial start--when the engine is cold, it is at 31 psi during idle, taxi, takeoff climb and cruise--and stays at 31 thruout everytime I looked at it. I don't know how long it took to come up at the cold start becasue I tie the tail down in front of my hangar and prop it myself. Last night I propped it and walked to the door and the pressure was starting to come up then. It could be that the line from the engine to the gage might be full of old thick oil and at lower temps it does not help the gage read right--don't know. The positive thing is that the oil temp seems to stay around 100 degrees F above the OAT at altitude.
If you have any ideas on this let me know.

Thanks,

Frank

[fearofpavement]

Re: Oil Pressure question

I have heard of a case where oil pressure fluctuations were caused by routing of the oil pressure line close to the exhaust.

One thing I would recommend is that after you refuel and have the lower oil pressure indications, go back out and fly it some more and see what it does. Remember that after you have been flying and taxiing with a hot engine the oil may be pretty warm and thus indicating lower.

If you haven't compared the oil pressure yet with another gauge you may want to do that. If it reads the same, bump up the pressure a bit to get more in the center of the operating range.

[alwaysoar]

Re: Oil Pressure question

Frank, You may also have a problem with your oil pump if it's taking that long to get pressure back up when you restart. Oil may be leaking out from the oil gears and thus it may be beginning to lose its prime. If you go an extended period of time, say a week or ten days, how does the pressure act? If you have to tip it on its nose or squirt oil in through the temp access to get pressure back, then it would be the oil pump. If you have air in the line, it would also take time to get back up as you have to compress the air. You are right to want to get to the bottom of this, but it seems to me you have a safe amount of pressure if you're getting pressure in 20sec and have 31 psi in flight.

[Gary Snell]

Re: Oil Pressure question

Seems the logical causes have already been suggested. If you've ruled out the other stuff, a plausible less likely cause could be the pickup tube in the sump is loose. I had a similar problem with my tractor hydraulic system leaking (sucking air) on the suction line to the of the pump after the oil was warmed. It drove me (and eventually the dealer) crazy trying to track down the problem.

Good luck!

[Forrest Barber]

Re: Oil Pressure question

You really do not adjust up and down. the oil pressure relief valve is set at ( I think) 38 lbs. on the Cont. A-65 . That is the maximum setting.
THEN any thing down from that shows, oil pump wear, engine wear, temp s, etc.....
My OH's run at 38 lbs. upon start up and stays there during flight, at idle after getting to "normal operating temp" they drop to 28-30 . As the engine wears, the idle oil pressure drops and can go clear down to 5-7 lbs , so long as it picks up to 25 & higher at cruise. I had a similar problem brought to me, it was the suction tube!! The idea of stretching the spring, or removing washers on the relief valve will not amke up for a problem with basis oil pressure. Try other guage, then check suction tube, then oil pump housing. Things do not just happen quickly, how about checking the relief valve itself and the seat for a piece of debris...

[Frank DeBartolo]

Re: Oil Pressure question

Thanks to all for the info. All the responses were thoughtful, informative and appreciated.

I don't know how long it will take my IA to get to my BC12-D and don't want to not fly the airplane if it can be flown without damaging the engine. From the way I understand it, I can fly it because it still is within the specs that are described in the above threads. So unless I hear otherwise, I will fly it.

Again, thanks,

Frank
N43684

[alwaysoar]

Re: Oil Pressure question

What does the Continental Maintenance and Overhaul Manual say on the subject of oil pressure?

"The pressure relief valve is set to give approximately 35 pounds of pressure at speeds of from 1900 to 2300 RPM."

"Oil pressure (idling) in Lbs/Sq.in (Minimum)...10"

Low oil pressure:

a/ Check for dirt in the oil screen. Remove screen and clean thoroughly.
b/ Check for poor connections in the oil suction tube, causing the pump to draw air.
c/ Check quantity of oil in the sump.
d/ Inspect the pressure relief valve to see if plunger is operating smoothly in its guide and seating well, and the control spring is functioning properly.
e/ Inspect and clean screen at end of oil suction tube.

Frank, have you checked your oil screen? That would be the easiest and you could do it yourself.

[Karl Rigdon]

Re: Oil Pressure question

Do not overlook the line from the engine to the gage. In some cases the line has a very small ID or a small orfice is installed to act as a snubber to lessen the shock to the gage. You should be sure this line is clear. With help you might disconnect the gage line at the gage and put the end in a jar. With that help you could start the engine and confirm the line was clear and had oil flow.
If the line is plugged or restricted the pressure rise and fall can be affected.

[Frank DeBartolo]

Re: Oil Pressure question

Thanks to all for the information. I flew the airplane yesterday, but this time the OAT was appx 40 degrees. I did a good preheat before flying. I did not experience the oil pressure problems I experienced last time. The oil came up within 7-10 seconds and popped up to pressure rather than coming up slowly. Oil pressure read a little over 30 during idle and takeoff. I flew for an hour and did four touch and goes. The oil pressure stayed at over 30 the entire time. After fueling and restart the oil pressure came up within 7-10 seconds and came up to 30. The only thing that was different between this flight and the prior flight was the preheat. My guess is that the line from the engine to the gage is filled with old oil and possibly gummy residue and when preheated, becomes lighter which makes the gage read more quickly--anyway I hope that that's what the problem is. The other thing is that at shut down after the engine is completly dead the oil pressure up stays up (the needle does not move) for several seconds then pops down to 0.

The IA is busy right now, and I wil have to wait till he can pull the oil line. I will keep all informed what we find out when we find out.

Again, thanks to all for the response and information. It makes it much easier to own a Taylorcraft--and gives me more peace of mind knowing that you all are out there.

Frank
N43684