I have a Fresh overhaul on a 0-360A1D from one of the most reputable engine shops with some very bizarre symptoms that maybe someone has experienced here? The problem is building sufficient manifold pressure to control the propeller once airborne. On ground run up the prop will cycle appropriately, however as soon as you get airborne you lose manifold pressure and the propeller control no longer seems to have any effect which makes it want to overspeed. You have to throttle back to not redline the engine. Makes for a fun go around to immediately land again! Propeller load seems to create or at least exacerbate the problem of insufficient pressure to the prop to adjust. Not the thing you want to be messing with when you should be breaking the engine in.

To make the diagnosis extra difficult, along with this new engine we initially put a new governor and composite propeller with the engine install. Assuming governor or prop to be the culprit we started by trying another governor with the same results, then my old propeller, with the same results. After weeks of testing we belive we have Isolated the problem to be somewhere in this main bearing area.

We then followed Lycoming service instruction NO. 1462 (Propeller Oil Control Leak Test Procedure) which essential entails building a test plate to go over the governor mount and testing the pressure over the main bearing. Under pressure the tolerance should be between 6-35 psi for an acceptable tolerance reading. We tested every which way and get zero. Complete blow by.

Governor oil plug in the crank is in place for constant speed propeller, and no obstructions in the oil lines. We pulled the oil filter and there appears to be more metal than your standard break in. 90% being non magnetic. Other than the wrong size front main bearing/journal, or hollow crank pins installed instead of solid pins can anyone think of another culprit?




I really hope that no one has to go through this incredibly painful process. We planned to log hundreds of hours this summer for work / pleasure and started this spring off with installing the new propeller and finding a hairline crack in my original engine crank case. This has turned in to an incredibly exhausting full time job that has cost a fortune and still there lies the plane with no engine on it once again. On a positive note I'm fast track learning my airplane.

Just to avoid doubt, are you saying the manifold air pressure (MAP) drops and if so, how much? Or does the oil pressure drop?

RPM and MAP have a strong relationship in flight, so a small drop in MAP could just be the RPM shifting as the governor becomes ineffective. I have no idea, but if you wanted a wild guess - it sounds like an oil system pressure issue, possible blockage or oil pressure control valve issue.

Correct. As soon as you take off. What appears to happen as a result of air load on the propeller you lose all ability to control using the propeller control and manifold pressure drops way off. Also once airborne oil pressure seems to be lower than it should be down near 50. Propeller seems to stay in fine pitch and the only way to avoid redline is to throttle back.

We didn't mess with the pressure relief, it does appear to make sufficient pressure on the ground. It really appears to be a pretty isolated problem internally at this point after weeks of testing things.

My reading and comprehension skills are not the greatest, so please accept my apologies in advance if this sounds weird, but I am having a hard time reconciling what you're writing.

First of all breaking ground does not load your prop (unless you are a new carbon cub owner trying to show the world your 'cub pointed at the moon routine') it unloads it. Second of all, your lower MAP is not causing your prop to overspeed, it is likely a result of the overspeed. A flat prop produces less MAP all else equal, which of course causes you to pull power further retarding MAP.

Your pictures aren't pointed the right direction, and this is probably the first thing you checked, but if it wasn't it should have been on a freshly delivered engine. Is the front crank plug gone, and the rear one not only intact, but undrilled? This engine can be ran fixed pitch or constant speed, and if the builder knew it was going on a cub they may have defaulted to FP even if you told them it would be constant speed/

You were on the right track with the governor, and since you know it wasn't the actual governor itself, you know it's the oil pressure to the prop.


Take care, Rob

The internal photo of the crankshaft indicates a CS setup. The rear diaphragm hasn't been "pierced" as outlined by the Lycoming Service Letter that describes conversion from a CS to FP setup.

Mapleflt wrote: The rear diaphragm hasn't been "pierced" as outlined by the Lycoming Service Letter that describes conversion from a CS to FP setup.

it sure would appear that way, and most likely is the case, only brought it up as an idea and because a 1/8 hole as the SI calls out will easily hide in the photo provided.

Take care,
Rob

Rob wrote:

Mapleflt wrote: The rear diaphragm hasn't been "pierced" as outlined by the Lycoming Service Letter that describes conversion from a CS to FP setup.

it sure would appear that way, and most likely is the case, only brought it up as an idea and because a 1/8 hole as the SI calls out will easily hide in the photo provided.

Take care,
Rob

Sorry if that sounded a bit "in your face" my apologizes. I wonder what the effects of a larger hole might be, I understood it was to be 1/8" as a minimum.

Damn, I sure hope your working with the engine builder during these "weeks" of testing. Otherwise I imagine they will tell you warranty void, if not.

Mapleflt wrote:

Rob wrote:

Mapleflt wrote: The rear diaphragm hasn't been "pierced" as outlined by the Lycoming Service Letter that describes conversion from a CS to FP setup.

it sure would appear that way, and most likely is the case, only brought it up as an idea and because a 1/8 hole as the SI calls out will easily hide in the photo provided.


Take care,
Rob

Sorry if that sounded a bit "in your face" my apologizes. I wonder what the effects of a larger hole might be, I understood it was to be 1/8" as a minimum.

Not at all. We're all good. I knew going in that the plugs should have been obvious, I was just hoping the OP would find that the 'fix' was something simple and obvious like this that got overlooked. And at the same time hoping to stimulate some participation from others to help the guy out with some ideas. I do get the warrantee concerns, and am hoping that was also an obvious concern that the OP just didn't translate in the start of the thread.

As for a larger hole? Man I dunno. I've seen them pierced, drilled, intact, and completely removed. My thought pattern with my query, was that let's start with a known point (what the factory prescribes) and go from there. And yes, you are correct, I am pretty sure the 1/8" is on the minimum side that the SI calls for.

Take care, Rob

We had a 550 come back from a very reputable shop with a completely botched O/H. By the time the diagnosing was done the engine was so bad that they bought us a new factory engine… hope your builder come clean with you in this.

Appriciate all the feedback here. Sorry for the slow reply with my travelling. It does appear that oil pressure is lower than it certainly should be, in the very least once airborne hovering around 50psi. Really the prop control has no effect when trying to adjust once airborne. It does seem to want to overspeed with this inability to control it. Sadly more downtime with the new engine on it's way back to the overhaul shop. I guess it's possible the plug was not installed properly but seems to be making more metal than a typical break-in i'm told. Concerning to say the least with 90% non magnetic metal. We tested my old 0-360 and got 10psi when preforming the 1462 service instruction. 6800 TT and 1200 TBO on that one too. Last thing we would have thought was the engine, so there was a ton of time testing old propeller, other governors before concentrating on the engine internals as to the problem. Shocked to hear others having issues with fresh overhauls!

While I don't really understand what is going on, a friend had his IO360 overhauled and the shop in Oklahoma that lapped and line bored the crankcase tapped into the oil galley and that made for a complete tear down after the first test flight low oil pressure.

Update here:
We are having the same symptoms as before! Far beyond frustrating at this point! After it taking a month for the overhaul shop to ship/receive back they indicated the (Main Thrust Bearing Surface was compromised) causing the problems on the first overhaul. They overhauled again and we received the engine back here OCT 17th. After the re-install and initial test flight we were getting nearly the identical problem to first overhaul. The only new symptom I can add from before is a clear 20psi drop when pulling the prop control in flight. It still wants to redline so we back off on the throttle and immediately land.

We started running through all these exhausting tests again. Thinking it's no way the engine could be assembled wrong again we started with the obvious things sending the governor off to two independent shops, sending the new prop to be checked over and flushed again, with no issues reported. No external leaks spotted we then Preformed the 1462A service bulletin again multiple times between test flights and it's hovering around an unacceptable 2psi currently. The 1462A test seems to progressively be getting worse, (psi drop). Pains me to say it's likely the same problem as the first go around overhaul. We're waiting to hear from the Overhaul shop.

At this point I've spent an absolute fortune and has been so incredibly time consuming I'm ready to be checked in to the funny farm. Clearly should have gone experimental and thrown a PT6 in her. . (Makes it far worse when you're engineer minded), Obsessed with researching and trying figure out what possibly could be happening. Ultimately glad no in flight engine failure.

I really appriciate the feedback before from you all and pray this doesn't happen to anyone else. For what its worth for you troubleshooting the same things I've been gathering other discussion forms that discuss trouble shooting. I will be sure to post here soon.

We just found out that there are two different gaskets for the Governor on our O-540-B4B5. The one sent to us from the Prop Governor O/H shop in Oklahoma was not the correct gasket for our application. Wacky indications. Make sure you have the half-moon screen and not the 3 holes in its place. Or maybe yours is the reverse??

A guy I know had an O-360 overhauled, while he was at it he had the shop convert it from fixed pitch use to constant speed.
He had the same sort of trouble afterward.
First was low oil pressure, turns out that there are some ports in the case that either get plugs, OR nozzles to squirt oil on the pistons,
depending on which model engine it is. The shop didn't install the plugs OR the nozzles.
Installing the plugs fixed the lack of oil pressure.
The second issue was the prop not cycling correctly.
The SB or whatever authorized the conversion from fixed pitch to c/s use called out for a passage in the case to be plugged (as I recall),
turned out that it wasn't. That let the oil divert back into the sump instead of supplying pressure to the front of the crankshaft.
Hope this helps.

I would really like to know what shop did the overhaul.

Kurt

Was the crankshaft sent out for inspection? I heard of a similar issue in a 206 turned out to be a cracked Crankshaft.
DENNY

A friend of mine got a new experimental 0-320 from a well known outfit who has a good reputation, this was about 15 years ago. He had it set up for a constant speed prop, it wouldn’t cycle the prop at all. After all the checks and tests it had to be sent back. The cause was the oil passage near the front main bearing that pressurized the oil passage leading to the prop had actually cracked inside the case, causing the pressurized oil to push directly inside the case. What are the odds?

185er wrote:A friend of mine got a new experimental 0-320 from a well known outfit who has a good reputation, this was about 15 years ago. He had it set up for a constant speed prop, it wouldn’t cycle the prop at all. After all the checks and tests it had to be sent back. The cause was the oil passage near the front main bearing that pressurized the oil passage leading to the prop had actually cracked inside the case, causing the pressurized oil to push directly inside the case. What are the odds?

Damn...that's a tough one to catch I guess unless you're looking for issues with the oil gallery. I had my 540 case inspected at Premiere in Troutdale and this has me wondering how closely they inspect those passages. I wonder what kind of forces are contributing to a crack there?

Gasket does have some questionable mating/ matching surfaces between this gov and drive gear but we've confirmed with multiple sources this is correct. Side note some others have had issues with this we have learned. Some dual mag setups require a plate between two gaskets as well. See Service Instruction No. 1438A