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Oil Pressure Drop to 0

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11 Oct 2022 16:59 #7 by Matt Gunsch
Replied by Matt Gunsch on topic Oil Pressure Drop to 0
have you tried hand lapping the relief plunger to the seat ? also, since you said this started when you installed the push rod tubes, the tubes themselves are just return lines, there is no oil pressure in them, the push rods do carry pressure have you checked that all the rods are seated correctly into the lifter bodies ?

A&P, IA, PPSEL
too many years GA and Warbird Maint
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11 Oct 2022 13:44 #8 by Super User
Replied by Super User on topic Oil Pressure Drop to 0
Randy, reach out to Robert Smith at Mena Aircraft Engines (479-394-7688). They are very good at these engines and may have something to offer in terms of advice.
The following user(s) said Thank You: Randy Branson

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11 Oct 2022 12:45 #9 by Randy Branson
Replied by Randy Branson on topic Oil Pressure Drop to 0
The saga continues.  We determined that cylinder #3 had a good bit of blow-by prior to the piston traveling to the bottom and the the exhaust valve opening.  So, I ordered, and we installed a NEW ($$$$) Millenium cylinder hoping that would stop the oil pressure drop by not "cooking" the mineral oil (single viscosity).  Nope!  Next, we replaced the oil pressure regulator spring and plunger.  Better cold pressure but at about 30 minutes into flight the pressure begins to drop to 25 psi (still in the green) and then to 20 psi (top of yellow, bottom of green on MY gauge).  Let it cool and the oil thicken, and pressure is once again up to 30+ until it gets to a temp of 175 or so, then it slowly drops to 25 psi again.   Only thing left is a new set of oil pump gears and cover plate.  I can locate old new stock gears but no cover plate whatsoever.

Keep in mind, I did not have any oil pressure issues until we did the top end starting with new STC'd push rod tubes.  I called Continental Engines, and the Tech reps just scratch their heads.  Any suggestions?

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21 Sep 2022 07:25 #10 by Randy Branson
Replied by Randy Branson on topic Oil Pressure Drop to 0
Thanks for the advice.  We used a bench tester and the gauge is dead on correct. 

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21 Sep 2022 03:10 #11 by Edward Moore
Replied by Edward Moore on topic Oil Pressure Drop to 0
I'm surprised but try another gauge, etc

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20 Sep 2022 22:06 #12 by Randy Branson
Oil Pressure Drop to 0 was created by Randy Branson
Just completed installing the Tennessee Real Gasket push rod tubes, new cylinder gaskets, bead blasted pistons, installed new rings, bead blasted valves and reseated them.  Filled with mineral oil and ground checked, no leaks.  1 lap flight, no leaks.  Compressions in the high 70's.  All's great right?  Nope.

I took her up for what was to be an hour of flying laps at 2500' and then checking for leaks.  On the third lap around around my oil pressure quickly dropped to zero and temp went over 220.  I immediately landed and taxied to the maintenance hangar.  No leaks, no oil traces.  Pulled the oil screen and it had a bit of carbon but no metal.  Pulled the oil pressure regulator and did find a fleck of carbon on the seating face of the plunger.  Great!  That's it.  Wrong.  Ran it up, good pressure.  took off and 3rd lap around same thing pressure drops to zero.

Checked screen...clean; check pressure plunger...nothing.  Drained the oil and flushed out the sump and fuel pressure seat.  refilled with oil.  Great pressure...until the 3rd lap then same thing.  My AP decided to drain the oil again and this time go to my normal Phillips 66 20/50 thinking the mineral oil is getting too thin and bypassing the plunger seat.  Good idea, but it didn't work.  Same result.

I called Contental's Tech support and talked to a really nice guy but he said it's a simple system, so wheat we did should have fixed the problem.  Only think he suggested was replacing the plunger, spring, and refacing the seat.  Ok, parts ordered...cant find the 88 degree cutting tool yet.

Can anyone give me any other suggestions?  This was not an issue before we installed new rings, pushrod tubes and gaskets.  HELP!!!

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