Advice on an O-300 with oil pressure issues (sad story)

pnwchief22 said:
I have first person experience with the aircraft being discussed. It has stc Electronic Oil pressure and oil temp guages. Transducer and associated flex hose was the first thing tested. Confirmed good, not the failure….Mid America A/P IA providing excellent service, especially considering his business is hopping and he is out twice a month maintaining warbirds. Substitute guage confirmed no pressure. Fresh oil with two new oil pump gears in the overhauled accessory case, same result. Screens clear.
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Well sounds like he doesn't need our help then :P
 
Roger Roger said:
Shrug. Seen lots of wires and pressure senders go wonky, never seen a direct reading oil pressure gauge quit or even be significantly out of cal.
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Had the hard line feeding the oil pressure gauge in a Cessna fatigue break and pump oil into the cockpit, thankfully it was during taxi and not in flight. Have read of this happening several times on other airplanes.
 
No. It's been a first owners/non-pilots nightmare. The other co-owner is on here. I haven't heard much lately but I think they ended up just overhauling it. The numbers were good on paper prior to buying it. They got a great deal on a 172 with a 400 hour engine. Did a pre-purchase. Did all the right things the way I see it. And it's been a disaster. Could have happened to me. I've bought planes on a general feeling without doing a pre-purchase a few times. I've been lucky.
 
DE727UPS said:
No. It's been a first owners/non-pilots nightmare. The other co-owner is on here. I haven't heard much lately but I think they ended up just overhauling it. The numbers were good on paper prior to buying it. They got a great deal on a 172 with a 400 hour engine. Did a pre-purchase. Did all the right things the way I see it. And it's been a disaster. Could have happened to me. I've bought planes on a general feeling without doing a pre-purchase a few times. I've been lucky.
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Bummer :(
 
rframe said:
Had the hard line feeding the oil pressure gauge in a Cessna fatigue break and pump oil into the cockpit, thankfully it was during taxi and not in flight. Have read of this happening several times on other airplanes.
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Makes sense that that happens, and I’m not saying it can’t, just that i never had it in the tens of thousands of airplane hours I was taking care of Cessnas, pipers, and beavers.
 
pnwchief22 said:
New oil pump gears and repaired the oil sump & accessory case while off the plane. Service bulletin issued in 1996 addressed some of the pressure indication.
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Does the O-300 have the same issues as the O-200 regarding the oil pump? I had a friend with a C-150 that would sometimes lose prime for the pump if it was parked at the wrong angle (AOA, and that just happened to be the angle of his hangar floor). He was finally able to get it fixed by changing the gears and the oil pump housing if I recall correctly.
 
pnwchief22 said:
New oil pump gears and repaired the oil sump & accessory case while off the plane. Service bulletin issued in 1996 addressed some of the pressure indication.
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Took 2 months? Shop schedule checks out.

My new mantra is fix it yourself, and then wait on an A&P to get the logbooks singed. Not any faster, but at least you know it is going to work after the ink is dry.
 
knot4u said:
Does the O-300 have the same issues as the O-200 regarding the oil pump? I had a friend with a C-150 that would sometimes lose prime for the pump if it was parked at the wrong angle (AOA, and that just happened to be the angle of his hangar floor). He was finally able to get it fixed by changing the gears and the oil pump housing if I recall correctly.
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I cannot say with any confidence that this was similar to the O-200 oil issue ( I owned two 150’s and never had a priming issue with those). This particular O-300 accessory case and oil pump appears to have been re-installed in field after the engine came back from signature in the early 2000’s. The documentation from those logbook entries and 337 is less than perfect.
 
drunkenbeagle said:
Took 2 months? Shop schedule checks out.

My new mantra is fix it yourself, and then wait on an A&P to get the logbooks singed. Not any faster, but at least you know it is going to work after the ink is dry.
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Singed? I don't know what A/Ps you know that just sign off work they either didn't witness or complete themselves. I'm going to go find a CFI to sign off a BFR post haste.
 
knot4u said:
Singed? I don't know what A/Ps you know that just sign off work they either didn't witness or complete themselves. I'm going to go find a CFI to sign off a BFR post haste.
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I have supervision and talk to someone before doing anything. Most of the effort is often finding out what's wrong in the first place though. Part 43 appendix A(c) encompasses a whole bunch.
 
pnwchief22 said:
I cannot say with any confidence that this was similar to the O-200 oil issue ( I owned two 150’s and never had a priming issue with those). This particular O-300 accessory case and oil pump appears to have been re-installed in field after the engine came back from signature in the early 2000’s. The documentation from those logbook entries and 337 is less than perfect.
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It was fitted with a newer sump prior to the engine installation in 2022. It is flying again with normal indications on the same electronic guages.
 
I made this account because of this thread and would like to give some information I've learned. Hopefully someone will see the information I have to offer and benefit from my struggle.

1. Check the gauge for accuracy
2. Check the line for damage or leaks
3. Check the fittings for debris and damage
4. Check the oil screens - both of them for debris and damage
5. Check the bypass valve for damage and debris - replace the spring regardless. (You can also leave the valve off and turn the prop by hand until oil comes out before going deeper (remove all spark plugs))
6. Check the pump gears for wear - you can remove the tach cable housing and check for play in the gear.
7. Remove valve covers - you're looking for even distribution of oil on the springs and the rocker arms.
8. Remove a cylinder - inspect the crank case for any cracks in the oil channels and any loose or missing parts.
9. Disassemble engine - going through all the other steps then it's time for an I.R.A.N. - look for excessive wear and any damage.

Brown stains are a sign of oil being cooked on the location and no oil flow over that particular spot.

In my situation, Joe Shmo did the "Major O/H". He overtorqued the fwd thru bolts and pinched the cam. Sending metal through the engine and destroying the oil pump gears and housing. The excessive metal in the oil well past break in was a sign, but tearing down the engine confirmed it.

I belive that the following information needs to be well known to avoid overpaying for aircraft and for the safety of pilot's:
Continental's manual M-0 outlines the basic Information needed for an O/H including required replacement parts. THRU BOLTS ARE REQUIRED TO BE REPLACED AT MAJOR O/H'S. You can look in the nose bowl and see if they are nice and new. ALL ACCESSORIES ARE REQUIRED TO BE REPLACED AT MAJOR O/H'S. You can look through the logbook. DO NOT BUY AN AIRCRAFT WITH POSTED LOW TIME S.M.O.H. UNLESS YOU VERIFY IT HAS BEEN DONE PROPERLY. There is more information in M-0, but if everyone knows to look for the obvious ones, then the hack mechanics will hopefully stop cutting corners.
 
O300runner1 said:
6. Check the pump gears for wear - you can remove the tach cable housing and check for play in the gear.
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I forgot to mention AD 72-25-02. Hopefully the photo is clear enough. The one at the top of the photo is the new design and the other is the old or original. Removing the tach cable housing from the accessory case will let you see the slotted part of the gear. It should end before the shelf, otherwise the AD was never complied with. The seal for the tach cable housing should be installed with flat side down when pressing it into the housing. You should be able to see the inside of the seal while looking at the mounting face of the housing. You'll have oil in your tach cable if it's backwards, and it can work its way to the gauge.
 

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DE727UPS said:
A non-pilot friend bought a 61 172 sight unseen out of Texas. He had a pre-buy done which turned into an annual. They even did a borescope on the engine. It was a good price and there was room for some investment. The ferry flight went through Hugoton, KS for cheap gas. After fueling, the ferry pilot got no oil pressure indication on startup, and shut it down. A mechanic from Liberal (I think) came out and found the oil pump had failed but likely no damage to the engine since it was shut down immediately with no oil pressure indication after starting. Ferry pilot goes home. Mechanic orders new oil pump and also says accessory case needs to be replaced, so finds another one somewhere. Engine goes back together and still no oil pressure. What to do now?

One option presented to the owner is a major overhaul. I suggested letting the mechanic dig deeper to fix the problem. I'm thinking there must be some blockage or clogging in the oil system. Now wondering if the oil pump was even bad in the first place?

I told the owner he should consider just pulling the wings off the thing and move it home to WA so he can be directly involved with further decisions and use a trustworthily local mechanic. The owner is part of a large family business that is a local fuel distributer and they have several big trucks. I'm trying to find out if they have a flatbed trailer in the mix.

Any mechanic's on here have any ideas on what the poor owner should do now short of doing a major on an O-300? Engine has 400 hours SMOH but the overhaul was likely done many years ago. I've owned 10 small GA planes and have avoided this nightmare aircraft ownership scenario. I was going to teach the owner how to fly this summer. For me, moral of the story is a pre-purchase or annual is no guarantee that something really bad might happen after you buy a plane. Maybe I've been lucky all these years.
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Serious question (no intention to be snide): Have you definitively determined that, in fact, there actually IS no oil pressure?
 
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