O-200 Centre Main Bearing Failure

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Bathman

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Bathman
My last 6 O-200 have failed to reach TBO all with centre main bearing failure. They fly on average around 450 hours a year. All fitted to C150’s all with Macauley props. Basically the oil pressure drops in the cruise and when hot at idle the oil pressure is next to non existent,

In one aircraft the main bearing failed failed at 1800 hours. Overhauled with new crank, new crankcase, new cam, all new cylinders. Main bearing failed again at 1200 hours. Rebuilt new crank, new crankcase, new cam, all new cylinders. The main bearing again failed again at 1200 hours and again it needed a new crank, crankcase and 4 new cylinders. Since the last rebuild it has done 200 hours and so far without incident.

Another aircraft had a cheap overhaul done by its previous owner in 2001 and it went all the way to TBO. Good quality rebuild with reground crank and original crankcase. New cam and cylinders. Main bearing failed at 1400. Since replaced with a factory rebuilt engine.

I brought another C150 with a factory rebuilt engine the main bearing failed on this after 1400 hours. Currently being rebuilt.

Finally my other C150 is showing the same oil pressure signs and I’ll be discussing it with my maintenance provider today. Its done 700 hours on a new crank, new crankcase and new cylinders.

I should add I have always used well regarded engine shops. About two years ago we changed from aeroshell mono-grade to 15-50W to see if that has made any difference. We always used a good engine shop, but we then changed to what most people would say is the best engine shop around (certainly the most expensive). We even tried the factory built route. Finally we have used a well respected local shop. But all seem to have given the same results.

We started fitting them with spin on oil filters again it doesn’t appear to have made any difference. The next suggestion we are going to work on is getting all the props dynamically balanced. However I am starting to think its simply the quality of the parts that are being supplied? Does anyone else have any thoughts?

I should add I’ve operated C150’s for many a year but never without the problems we are now having.
 
are these working airplanes? rentals?
what rpm are they run at?
anyone checked the max rpm using an electronic tach?
what part of the country, what temps are they flown in?
preheat if cold winters?
what oil P are they set to?
has anyone noted oil T in cruise?
oil additives?
Just some ideas that come to mind. I have no idea if they are relevant in your situation.
 
Yes.
2450rpm
25 to 75 F
Never preheat. But never really cold
Oil pressure always smack in the green - initially
Oil temperature oilways spot on normal
No oil additives. Either originally aeroshell 80w now aeroshell 15-50w.
 
My question is why only the center main?
 
Wouldnt hurt to run this past the CAT (continental) tech ppl. They may have heard of it.
 
Bathman said:
Yes.
2450rpm
25 to 75 F
Never preheat. But never really cold
Oil pressure always smack in the green - initially
Oil temperature oilways spot on normal
No oil additives. Either originally aeroshell 80w now aeroshell 15-50w.
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there is your problem.
 
Tell us more what's the answer?

We only switched to 15W50 after 5 engines failing to make TBO
 
Interesting. My 150 is at 1900 since overhaul in 1989.
 
I haven't heard of this at all. And I have used both W80 and 15W50 Aeroshells in them, no trouble. Is someone doing unauthorized aerobatics, with the gyroscopic precession forces bending the crank enough to load up that center main? And which would result in periodic oil starvation? That center main is, I think, the most highly loaded bearing in that engine. I think.
 
Bathman said:
Does anyone else have any thoughts?
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If I understand you, you’ve never had this problem until that last 6 engine OHs?

And you either externally sourced an engine or had different shops OH the last 6 engines?

Define “failure”—catastrophic or gradual, i.e., found metal during oil change?

Were all 6 failures identical in nature?

How much PSI is oil pressure dropping in cruise? ( hot oil low pressure at idle is common—at cruise is not)

At any time did you track the oil analysis or had the oil analyzed after a failure?

Within your fleet what are the common factors between the last 6 engines/aircraft, i.e., mx provider, pilots, type usage, etc.?

Have you pi$$ed off anybody prior to the last 6 OHs?
 
It is a well known fact the 0-200 doesn't play well with aeroslime.

I thought every one knew that, and the key start starters only gets 200-300 hours before they have problems.
 
The oil clearance on a 0-200 is .002" normally the 15/50 aeroshell is too thin to protect the Babbitt bearing.
Our 0-200s get over 1800 hours on Phillips 20W50. with no starter clutch problem.

just a fact, don't try to rationalize it, it just works.
 
Tom-D said:
It is a well known fact the 0-200 doesn't play well with aeroslime.

I thought every one knew that, and the key start starters only gets 200-300 hours before they have problems.
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Tom-D said:
The oil clearance on a 0-200 is .002" normally the 15/50 aeroshell is too thin to protect the Babbitt bearing.
Our 0-200s get over 1800 hours on Phillips 20W50. with no starter clutch problem.

just a fact, don't try to rationalize it, it just works.
Click to expand...

Didn't know that Tom.
 
jbDC9 said:
I suspect most people didn’t know that.
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They should by now.. Gotta remember the 0-200- C-series were engineered in the 30, made to run 50 weight mineral oil. --- that was all they had and they ran well, most to 1800 and beyond.
 
semi-synthetic multigrades are not made for the 0-200.
The starter clutch needs friction, or it won't work.
pull starters don't have the problem they don't have a clutch. except the main bearing still fails
 
Tom-D said:
They should by now.. Gotta remember the 0-200- C-series were engineered in the 30, made to run 50 weight mineral oil. --- that was all they had and they ran well, most to 1800 and beyond.
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upload_2020-7-31_16-51-39.png

Aeroshell 15W50:

upload_2020-7-31_16-54-16.png

Here's the dope on W100 and 15W50. Note 15W50's kinematic viscosity at 100°C (212°F): 19.6 cubic millimeters per second. The W100 is an SAE 50 oil and its viscosity at 100°C is 20.2. Both are in the range for SAE50 (Aviation 100) oils. The multigrade shines at the lower temps, with the differences in viscosity and pour points being pretty stark. That's where you want oil that the oil pump can suck up and get to the critical areas when the weather is cold.

There is no reason to suggest that 15W50 runs thin at operating temps, and if it was a problem in destroying engines there'd be an AD on it. It's additive can
make those old clutches slip after a while, though.

I ran 15W50 in my A-65 after I'd been running straight-grades, and saw the oil temperature fall as much as 30°F.
 

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You don't need to like it. and you can rationalize it any you like.
Phillips 20W50 and 25 hour oil changes is the best way to go.
semi-synthetic multigrade is slime in my opinion.
 
Maybe give CP Aviation at KSZP a call, they have run a fleet of 150s for their training operation for decades, plus they do all their maintance in house.
 
G-force said:
Maybe give CP Aviation at KSZP a call, they have run a fleet of 150s for their training operation for decades, plus they do all their maintance in house.
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152s ?
 
Dan Thomas said:
View attachment 88446

Aeroshell 15W50:

View attachment 88448

Here's the dope on W100 and 15W50. Note 15W50's kinematic viscosity at 100°C (212°F): 19.6 cubic millimeters per second. The W100 is an SAE 50 oil and its viscosity at 100°C is 20.2. Both are in the range for SAE50 (Aviation 100) oils. The multigrade shines at the lower temps, with the differences in viscosity and pour points being pretty stark. That's where you want oil that the oil pump can suck up and get to the critical areas when the weather is cold.

There is no reason to suggest that 15W50 runs thin at operating temps, and if it was a problem in destroying engines there'd be an AD on it. It's additive can
make those old clutches slip after a while, though.

I ran 15W50 in my A-65 after I'd been running straight-grades, and saw the oil temperature fall as much as 30°F.
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Then why do see the number failures? I'd bet you would see the temp drop with Phillips, with out the failures.

The reason I believe the way I do is because I have seen the results, not somebodies info sheet
 
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Harry Fenton has a few things to say about the subject. Scroll through the index, oil pressure problems are a ways down.
http://www.bowersflybaby.com/tech/fenton.html

Make sure the oil pump and case are in very good condition at overhaul, not just in limits.
 
Tom-D said:
The 152 doesn't have a 0-200 engine.
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No kidding. I think your confused, go back and read my post that you quoted. I never said 152. I said 150s.
 
I agree - a great resource. I believe he worked at TCM for many years.
 
JAWS said:
H
Make sure the oil pump and case are in very good condition at overhaul, not just in limits.
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This is very important, and OBTW it's getting hard to find good accessories cases.
 
JAWS said:
I agree - a great resource. I believe he worked at TCM for many years.
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He was also at Slick mags for 20 years, has a lot to say about Case and Eisman mags
 
JAWS said:
I agree - a great resource. I believe he worked at TCM for many years.
Click to expand...

I’ve been concerned that info will be lost if he ever departs; any way to archive it now? (It helped me when I had a 150.)
 
Ive got the low down. Its not been stripped yet but they think its the centre main bearing.

All the engines displayed the same signs with low oil pressure in the cruise. Out of the green and when up to temperature no more than 20 psi. Then vacating the runway the oil pressure is zero.

We haven’t ****ed anyone off and don’t owe anyone any money. We have even been though the security cameras. Our overhauls for years have been done at one of the largest shops around. We then switched to the one that's more expensive and now we are using a brother and brother outfit that specialises in small continentals.

It hasn’t got anything to do with 15W50 as we have only switched to that 2 weeks ago. For years we used W80 with W100 for a couple of months in the summer.

Speaking to the brothers they say they are seeing this a lot of this these days. They think its the crankcases that are just old. There all from a overhauled by a well known crankcase supplier and they think 90% of them have had weld repairs.

They also say this happens a lot less when a wooded prop is used.
 
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