OIL Pressure Increases in Flight

Hello,

I have a Superior XO-360 with ~200 TTSN

20 minutes in to a recent flight after normal oil pressure during run up and take off, the oil pressure warning alarm sounded. The oil pressure read 101 on the Dynon D10 EMS.

I backed off on the RPM and pressure remained high for a bit then came down to low 90s then back up to 94.

I landed at my home airport and tested the oil pressure sensor with compressed air and it was functioning normally. All pressures on my air pressure gauge and the Dynon were within 1-4 psi of each other. This rules out a transducer issue. Yes, I know that Dynon now uses a different transducer, but this is not the issue.

I backed the pressure regulator screw out about three turns and lowered the overall pressure for idle ~60 psi and ran up to 2000 rpms and it was ~84 psi.

I flew a couple of subsequent flights and the pressure was within normal limits ~80-85 in cruise 24x24.

Today I flew with a passenger and the pressure on takeoff roll was 101 and only came down to about 97 in cruise the alarm was sounding during the whole flight. I backed off prop RPM and it remained in low to mid 90s.

Having ruled out the pressure transducer, what else could be causing this?

Thanks in advance,

Mike

Mike, I had similar symptoms recently. New transducer fixed the high pressure reading issue. Your method of checking it with air pressure while on the ground might be inaccurate.

Temperature sensitive sender?

Temperature sensitive sender?

Sounds like a blockage somewhere. Under normal operation, you should never have to loosen the pressure regulator spring. Your oil pressure can only increase (assuming same viscosity and temp) if something has restricted the flow beyond your normal "steady state" or you regulator ball has stuck closed. The fact that it crept back up after loosen the regulator indicates the problem is getting worse. It also confirms that your ball is not stuck closed, but still could be hanging up on a burr or built up debris.

A blockage means something is possilbly not receiving as much oil as it needs or should have. I would not fly until you resolve this issue. It might be worth your while to test the sensor again to be certain, as most of the alternative causes are unpleasant and potentially hard to find without a tear down. You can also connect a low cost 1/8" npt based sensor into the forward oil galley clean out. This would also help to identify a blockage in the main gallery or verify the other sensors accuracy.

It is also possible that you have some damage in the pressure regulator that is causing it to hang up. If the ball can't move off the seat enough, the appropriate amount of excess flow cannot be relieved and you get a higher pressure. Several versions have a cage that the ball moves in and I vaguely remember only a moderate clearance. I would go here next after verifying the sensors accuracy.

How many hours on the engine? How often do you changer your oil?

EDIT: The intermittancy of your issue points to a sensor issue and I encourage you to spent a bit more time confirming the accuracy of the data your getting.

Larry

Just had the same problem and fixed it. I also have a Superior io360 and the pressure transducer is mounted on a Vans supplied manifold on the firewall. Researched the problem on my EFIS manufacturer's site, MGL. They indicated the single wire transducers develop ground problems over time. Recommend brazing a wire to tranducer case and grounding directly to the engine. I did this and problem solved.

Sounds exactly like issues I have had. Fixed with a new transducer the first time. The second time I decided to try just cleaning and tightening all the contacts. Problem solved again.

Chris

Be careful adjusting the engine oil pressure based upon the electrical sender. They are notoriously innacurate once they start exhibiting the sytems you mention here. Did you install the restrictor fitting in the line to the sender? That really helps with a better indication and increasing the longevity of the senders. Otherwise, the pulsing from the oil pump causes the arm inside the sender to move back and forth, thereby wearing it out in one spot.

It's best to check with a mechanical gauge, and as others mentioned already, make sure you have a good ground to the sender. A poor ground will normally cause the senders to read high.

Vic

I've got a flakey fuel pressure sensor. Next time the cowling is off...

Which style of pressure transducer? The VDO single-wire jobs are POSs, IMHO.

Had a similar problem at about 100 hours...pressure would start to read higher in flight, tripping alarms. This was on a brand new YIO-360-M1B, so rather than mess with the engine, I swapped out for a new VDO. Problem fixed. For a while, then about 100 hours later, same symptoms.

Installed the Kavlicos for both fuel and oil. Rock solid now at 500 hours and counting.

My vote is the transducer (like others, I don't think your test is valid).

Sender...

I started experiencing unexplained periods of oil pressure >99 psi. Normally reading in the 80's. Changed OP sender, now it's back to normal. Target rich environment is the sender.

Thanks everyone for the posts. I took a look on the VDO site. They caution against using teflon tape or thread sealer as this affects the ground....


Any comments?

McPilot said:

Thanks everyone for the posts. I took a look on the VDO site. They caution against using teflon tape or thread sealer as this affects the ground....


Any comments?

Click to expand...

I used a SMALL amount of Permatex #2, as I'd rather deal with sender ground issues than oil leaks. Then, I used a hose clamp to clamp a ground wire with a flat terminal against the body of the sender, which was then run to a bolt on the firewall. The last time I had issues, I took off that ground wire, cleaned the terminals, re-clamped, and problem solved.

Chris

I used to have similar problems...

With single connection senders, those that use the case for the ground.

I then changed to senders with two connectors, one for signal and one for ground. I never had a problem after that.

YMMV

Kavlicos/RV7A Flyer

RV7A Flyer

Could you expand on which Kavlicos units you used and where you purchased etc... I'm looking for a oil pressure transducer. I also have had VDO units and they are pieces of *%#.
Thx.

Rod
RV8,
BPE IO-360,CS

I have a vdo oil pressure sender with a ground soldered to the case. I recently had a high oil pressure warning as well and a few small taps on the sender with a hammer solved the issue;

Bill

Go Guy said:

RV7A Flyer

Could you expand on which Kavlicos units you used and where you purchased etc... I'm looking for a oil pressure transducer. I also have had VDO units and they are pieces of *%#.
Thx.

Rod
RV8,
BPE IO-360,CS

Click to expand...

You probably know this, but your EMS must support the Kavlico in order to change. They are not interchangeable. The VDO is a resistive sensor and the Kavlico is a transducer, providing .5 - 4.5 volts.

Larry

McPilot said:

Thanks everyone for the posts. I took a look on the VDO site. They caution against using teflon tape or thread sealer as this affects the ground....


Any comments?

Click to expand...

I use permatex #2 and never had a problem with grounds. Cant speak to the conductivity of teflon tape and it has no place as a thread sealant on an engine. I would expect it to create problems. Liquids can squeeze out of the thread interface, but teflon tape cannot and the plastic carrier tape is likely to remain as a barrier between the threads, creating a conductivity issue.

If your threads are in good shape and properly tapped, you should be able to get a good seal on NPT threads without sealant. The primary purpose of thread sealant on NPT threads is friction reduction (this is why teflon works even though it is not known as a sealant). Without them, you need to apply a significant amount of force while tightening in order to get a leak free seal. Many people are uncomfortable applying that much force.

Larry

SOLVED!

The Mitchell oil pressure sender from Aircraft Spruce did the trick. It has two terminals. One for instrument and one for ground. This has finally solved the problem. I flew twice since installation and both times the oil pressure was rock solid.