High Oil Pressure causes

RVG8tor · #1 05-31-2013, 06:45 PM

Along about my 50th hour my plane started to have high oil pressure on the first flight of the day. The first time happened on takeoff, I went around the pattern and landed. I took the cowling off and looked over things and suspected a bad sender, I still had the Dynon single wire sender. Suspecting the sender I went and flew and not alarms.

I had already bought the newer 3 wire sender when I had a pad fuel pressure sender out of the box and learned Dynon no longer carries the old one wire sender. The next day I changed to the new sender then all was good for the next flight and a couple after that. Then it came back initially it would be on the first flight of the day and I would get it during takeoff, I learned to ignore it a while and it would go away eventually, I never get it on the second flight after a fuel stop.

Now I get the high pressure alarm on the ground, it pegs high or nearly so and then drops fast to normal the climbs, last flight after sitting for 2 weeks I flew for 15 minutes before it settled down to normal.

This morning after a week off it gave it to me on the run up but was normal by the time I took off.

I warm the oil before flight, usually it is 80 plus degrees. But I have flow once or twice when away from home and can't see a correlation on this one.
I have checked the wires and all are good, but I did not ohm check anything, since I don't know what numbers I should see.

It was fine the first 50 hours, perhaps something happened in the oil change, I did remove and check the oil screen on the first couple oil changes. Last time was 7 hours ago, this was at 90 hours, I can't believe I have flown this much since December!

Consumption is good, 7 hours and only down a half quart since the last oil change.

Inflight after it settles down I have 80 psi and 180 degrees for oil parameters.

Flew today and after the run up all was good for two hops.

If anyone has any ideas I would really appreciate any help.

tadsargent · #2 05-31-2013, 06:53 PM

What is the value. High is subjective. I start at north of 100 psi but settles to
95 or so in cruise, More is better
YMMV

fixnflyguy · #3 05-31-2013, 08:16 PM

My values are the same as Stripes are indicating...100 plus on TO and climb, 90 or so in cruise. Pressure is only on the stuff that needs it, and isn't going to blow seals, as they are all on the vented side of the crankcase.

mannanj · #4 05-31-2013, 08:42 PM

On another brand, pressures will run high if you have a faulty ground connection. Check ground connections at the EFIS itself and sometimes anodized aluminum threads on the sending units don't make good grounds where they screw in.

intermittent ground connections can cause intermittent false high readings. If you can't find anything, try a plain old analog pressure guage to double check pressures.

RVG8tor · #5 05-31-2013, 10:30 PM

The pressure pegs the gauge most of the time, which is set with a high of 145 but I can see it move up from normal to the high, this only takes a second or two.

It looked like a wiring problem but I have not found anything wrong and this is all new parts so there has been not time for corrosion to set in.

Not sure why this would only happen with the first flight of the day if it were a wiring issue.

jim miller · #6 06-04-2013, 05:33 PM

I have been told my a long time A&P that high oil pressure is worse than being a little on the low side. This is due to excessive wear from the high
pressure oil on the bearing surfaces. Lycoming gives a recommended max
oil pressure and makes no mention that more is better. I think something
around 80psi is recommended. I guess his theory is like the water jet principle where high pressure water can cut
1/2 inch steel. Experts please correct me if this is incorrect.

JM

fixnflyguy · #7 06-04-2013, 07:59 PM

If you look at the oil pressure path, the bearings and valve train get the direct pressure, all else is basically splash. There is no direct pressure to a seal or gasket. The most vulnerable component is the oil cooler and lines. The comparison to water jet similarity is apples/oranges, as the water jet uses water at several thousand psi, with a slurry of abrasive such as steel or other grit...the water just carries the cutting media. I am not an expert by any means, but like my pressures on the high side...always like hearing from true engine gurus that may chime in.

rocketbob · #8 06-04-2013, 09:09 PM

I like high oil pressure. A typical waterjet pump takes a 50hp electric motor to run the pump and the pressures are in excess of 50K psi. Bearing erosion is not a concern in a slow revving motor like a Lycoming.

jim miller · #9 06-05-2013, 05:38 AM

Quote:

Originally Posted by fixnflyguy

If you look at the oil pressure path, the bearings and valve train get the direct pressure, all else is basically splash. There is no direct pressure to a seal or gasket. The most vulnerable component is the oil cooler and lines. The comparison to water jet similarity is apples/oranges, as the water jet uses water at several thousand psi, with a slurry of abrasive such as steel or other grit...the water just carries the cutting media. I am not an expert by any means, but like my pressures on the high side...always like hearing from true engine gurus that may chime in.

I wasn't trying to make a direct correlation to a water jet cutting machine. I would have to wonder why Lycoming gives us a way to minutely adjust oil
pressure instead of just taking the max the oil pump can give?

rocketbob · #10 06-05-2013, 07:32 AM

Quote:

Originally Posted by jim miller

I would have to wonder why Lycoming gives us a way to minutely adjust oil
pressure instead of just taking the max the oil pump can give?

Because they are old-school and only make mediocre improvements to anything. All it takes is a longer housing and a longer screw to get more adjustment range.