Oil pressure run-away

[n502pd]

On the second flight today, after about 20 min, and throttle back for the decent to downwind, the oil pressure climbed well above the red line of 80psi, and almost reached 100 psi before I pulled power way back, which brought it back to less that 60 psi, but not down to idle pressure of around 25-30 psi. this sortie was to climb to 3500 and do stall series, which I did begin.I made rapid landing (not a real pretty one) but on ground and can use Sirpeedee again, and the seat was clean!!! After shutdown and short wait, oil level checked and was fine. color good. engine ran and restarted without problem. But oil pressure was rpm dependant...no regulation...kept climbing as rpm increased. Oil temp was 200 or less, but came down to about 160 durring decent when this happened. Too rapid of decent??shock cooling??Dont think so. But I am open to ideas.

What I suspect is that the pressure regulator has stuck closed because of a new engine and new plunger. No washers installed under spring. Or heaven forbid...a bearing insert has shifted and partially blocked its passage.

Who has had this problem and what was found, and what was done to fix it?

Thanks!

[MichaelFarley56]

Joe,

My guess is one of two things. Do you have a digital gauge with a VDO sensor? In around 250 hours, I think I'm on VDO sensor #6. I carry a spare now just in case. If it's flickering a lot that may be it.

Otherwise it sounds like your oil pressure regulator plunger and/or spring has jammed. That's the flywheel side one; pull it out, clean it with an emery cloth so it moves freely, then reinstall.

Good luck! Let us know how it goes.

[SonexN76ET]

The high oil pressure could be a stuck oil pressure relief valve or very likely a faulty oil pressure sender.

It is unlikely your oil pressure could have actually gone to 100 PSI as the pump won't develop that much pressure. Likely your VDO oil pressure sender only reads up to 80 psi.

It is also highly likely that your oil pressure sender is not getting a good ground. You may need to string a ground wire to the base as the magnesium case and dissimilar metals, paint, and sealants all conspire to prevent a steady grounding of the pressure sender.

I would install the ground wire, polish both oil relief valves, and order a replacement sender in case the first two steps here do not work.

Many people have experienced multiple failures of the VDO oil pressure senders. Some have opted for a gauge that uses an actual oil line going to it to monitor oil pressure.

When you change out your sender, make sure to clean out the port and remove any metallic speckles in there that may get trapped in that one way orafice.

My apologies to Mike. I think we were typing at the same time!

Jake

[kevinh]

Yah - I had a very similar experience on the first flight of my RV7. In my case the oil temperature sensor died (though it had been fine on previous test runs - the vibration of flight exposed some problem). Super stressful, landed did some testing (put sensor in boiling water and the water was somehow boiling at '400 degrees').

[n502pd]

Thanks for the replys, but my OP gauge is a capilary tube (copper) direct reading gauge, so the electric discussion isnt correct. I forgot to mention that in my original post! With this capillary tube gauge I feel that I am getting the unadulturated situation on pressure. I am monitoring the pressure from the front port near the right side of the case, and is very dependant on rpm, where as on take off it was showing normal operation. The one failure point in this setup is the gauge itself, where the internal gears have slipped or the needle has come loose, but at this juncture, I do feel that the piston inside the rear regulator is stuck. I am going out to see if that is the problem about noon CDST today. I will post what I find for sure.

thanks to all for the replies! It is appreciated!

Joe

[n502pd]

Good morning to all!! I did find that both regulator pistons, the rear one and the front one, were not freely moving. I highly suspect residual particles from case internal passages to be the cullprit(s) here. One very interesting thing I did find was the outer diameter of both springs used, where they were cut to length and ground flat to seat perpendicular to the piston base, was not the same diameter as the rest of the spring body. The cut off end of the spring coil was in worst cast .008-.010 in bigger, and where the grinding operation was done, the outer edge of the coil had a sharp edge. I am thinking that this larger diameter and sharp edge was root cause of the trash that caused the sticky piston. For those still building AeroVee, check this spring(s) ends for sharp edges and larger diameter last 1/2 coil ends. I used a dremel to gently recontour the end and made sure all was smooth with scotch bright treatment. I also, of course, polished very slight damage to piston with same proceedure. I did not treat anything within the block bore. I could not see any marks, but its very hard to visualize after engine run. I have some phone pictures of the springs. Please email/pm me if you wish to see them.