Peeling the Onion

[MBDiagMan]

I think the time has come to freshen the O200A that is in my beloved Cessna 140. Financially I could never justify the expense in a million years, but I thoroughly enjoy this airplane. It is not a typical 140. It was caringly restored and upgraded with a custom IFR panel, the O200, 150 seats and other upgraded components. It is rigged incredibly well and is still a rag wing. It is a 48 model which means it has several improvements over the earlier versions. All that said, to most anyone else it’s probably just another old plane, but to me she’s part of the family.

The engine is past TBO by a couple of hundred hours and I have been nursing it along with kid glove care, but there are multiple signs of age and experience. The oil pressure has run at the bottom of acceptable limits for quite some time, but it appears to now be slipping slightly lower to a point being below factory limits. In cruise it hangs right at 30 PSI, but occasionally has been slightly below that. At hot idle it now goes below 10 PSI.

The engine is leaking and using a lot of oil. The pushrod tubes are leaking which means the cylinders have to come off to fix those. They have always leaked slightly, but they are leaking a lot more or there is an additional leak to be found.

The engine now feels like it has a weak cylinder. A few months ago, I had a cylinder go dead on take off when too far down the runway to set it back down. It climbed at a few hundred feet per minute, so I got it back in with no problem beyond a temporarily accelerated heart rate. Once on the ground after the throttle has been pulled back, running it up on the ramp it ran fine and this has not repeated itself. In researching this with the O200A guru Harry Fentons massive information, I learned that this was probably a hydraulic valve unit.

The engine is nearing 2000 hours and only one of the cylinders have been dealt with during that time. The engine has Slick mags in great shape. The carburetor, alternator, starter, vac pump and other accessories are in good shape.

So now, here we are. If I do write this unjustifiable check, my inclination is to remove the engine and send it or take it to one of the shops that specialize in engine rebuilds. With no experience ever having gone through this, I am soliciting comments from those who do this kind of work or have gone through this as an aircraft owner.

Thanks for any comments and advice.

 

[murphey]

Zephyr engines in Florida. I regret having it done at a closer to home shop. Altho Charlie Merlot’s retired, he still hangs out here on PoA.

 

[MBDiagMan]

Thanks Murphy! I will check them out.

 

[Tom-D]

The crank is .010 under on the mains, standard on the rods, rod are re-worked by ASSI, as were the cam and lifters. Cylinders are new superiors, case was reworked by crankcase services.
Total time unknown, Zero Time Since Major Overhaul to rebuilt standards IAW 43.2.

Price $15,000 delivered

 

[MBDiagMan]

So Tom, are you offering it at that price or simply pointing out how much it cost you? If you are offering it at that price, I assume it is an outright price, not exchange?

 

[Tom-D]

So Tom, are you offering it at that price or simply pointing out how much it cost you? If you are offering it at that price, I assume it is an outright price, not exchange?

That is an out right sale.

 

[MBDiagMan]

And that is as seen in the picture with no accessories? Does it have new hydraulic valve slack adjustersor whatever they are called?

 

[Tom-D]

And that is as seen in the picture with no accessories?

Yes, I'll configure the engine with any accessories you like at cost of the accessories.
This engine has not been run on the test cell because there are no accessories for it.
It will require installation and testing prior to meeting FAR 43.2 requirements.
That is why it is 15k not the normal 18k.
Price is Ferm, I have more than this in it.

 

[MBDiagMan]

Okay, I understand. Does it have the new hydraulic valve units?

 

[Tom-D]

Okay, I understand. Does it have the new hydraulic valve units?

reground, hydraulic units, cups, and lifter bodies.
Rocker arms are re-bushed, honed to size and new shafts came with new cylinder kits, and new piston pins were installed.

 

[Tom-D]

It comes with a set of new mount hardware and rubbers, and a used vac pump.

 

[MBDiagMan]

I knew I had read somewhere that the Hydraulic Units are supposed to be replaced at overhaul time and I didn’t remember what they were called. This is what Harry Fenton said, and probably applies to my power loss on climb out incident, so that’s why it catches my attention. Tom if you have time to read it, I would appreciate your interpretation and comments. It sounds as if most rebuilders do not replace them at overhaul.


Harry Fenton answer to a question:

Misfire/RPM Loss After Takeoff
I have a Cessna 150 with an O-200A (licence built rolls Royce). About 18 months ago the aircraft developed a misfire on the climb out from takeoff The misfire appears to get worse in the summer and improve in colder weather. It is normally a "smooth" misfire - it feels like one cylinder is dropping out. There is a significant increase in vibration. It only occurs after takeoff, I cannot repeat the problem in a full power climb from the cruise, nor can I repeat it on the ground, however in summer it goes almost every time on climb out. Typically it starts about a minute after lift off at a few hundred feet, although it has on rare occasions started to misfire on the takeoff roll. I normally get an indicated 2400rpm static, rising to 2500 on the takeoff roll and maintaining 2500 in the climb. When the misfire starts, RPM typically drops to 2300 and the climb rate drops by around 200fpm. When it clears, the RPM immediately recovers to 2500. Switching magnetos while it is running rough only causes the expected RPM reduction, it makes no difference to the roughness. Leaning the mixture generally makes little difference. Pulling the carb heat out does make the engine run even rougher, but unlike with carb ice it doesn't clear, it just continues to run rougher until you put the carb heat back in, at which point it carries on running as roughly as before you pulled it out. However, throttling back slightly to reduce the RPM generally allows the engine to recover after a few seconds - thereafter you can usually go back to full power to continue the climb without a problem.
On very rare occasions (typically very warm days), the rough running has become worse than this with a much larger drop in RPM and severe general roughness although it has never quit completely. On each occasion, closing the throttle slightly has allowed it to recover as described above. These may be a bit spurious - I'm not sure if these "atypical" episodes have been the same problem, or have been combined with carb ice or similar which the aircraft is quite prone to.
At the time it was thought to be a sticking valve (the engine had apparently had a history of a sticking valve problem some years earlier). The cylinders were due for an overhaul, so I had them all replaced with Superior Millennium, however this made no long term difference (it did seem better during the break-in time of the new cylinders though, during which I believe it was run on straight 80 oil). The carburettor has been overhauled, then replaced with a new unit, still no effect. The mags, ignition harness and plugs have also been replaced with brand new units with no success. The aircraft has had 2 annual inspections during this period so things like the air filters have also been replaced. Nothing else has been found wrong, everything seems secure (inlet pipes, exhaust system etc). We have done fuel flow checks from the gascolator-carburettor hose. The system has delivered 200% of the maximum fuel drain required by the carb for more than 10 minutes, even with the tail strapped down to put the aircraft in the climbing attitude and with the fuel tanks running close to empty. The flow rate remained steady throughout the test.

The only pattern I can see other than the temperature dependence is that the problem has appeared to be worse since switching to a new maintenance organisation, and they have switched from W80 oil to W100 oil. My previous maintenance organisation told me they used W80 because of the previous sticking valve history. Having switched back to W80 oil myself the problem seemed to be getting slightly better on each subsequent takeoff, although it is still there at present.

The only parts which we have not replaced which I can see could be a possible cause of this problem are the hydraulic valve lifters. I have found various references around the internet to people experiencing similar symptoms which have been found to be a lifter either collapsing or pumping up. Having already spent a lot of money trying to fix this over a long period of time, I was looking for some advice before spending even morereplacing the lifters.

Any advice or help which you could offer me would be very gratefully received.

Before I even got past the few lines of the second paragraph, I suspected that your problem might be the hydraulic lifters. The hydraulic units commonly cause the problem which you have described. Over time, the hydraulic units will stick and simply not open the valve completely and the result is an rpm loss.

You can perform a leakdown check of the lifters by pumping them up with solvent. The lifter should maintain pressure over a period of five minutes. If not, then that hydraulic unit needs to be replaced. However, this test is not entirely perfect in detecting a bad HU- it just sorts out the obviously bad parts from good parts. A HU which passes the test can also stick over a period of time.

Continental specifies that the hydraulic units are to be replaced 100% at every engine overhaul, but it is not unusual to re-use these units over a period of several overhauls. The problem is that eventually the hydraulic units will fail.

Given that you have replaced virtually everything else on the engine which could cause this problem, it is reasonable to assume that the hydraulic units will need to be replaced.

Harry

 

[Tom-D]

I knew I had read somewhere that the Hydraulic Units are supposed to be replaced at overhaul time and I didn’t remember what they were called. This is what Harry Fenton said, and probably applies to my power loss on climb out incident, so that’s why it catches my attention. Tom if you have time to read it, I would appreciate your interpretation and comments. It sounds as if most rebuilders do not replace them at overhaul.
Harry

I don't know of any overhauler that replaces good lifters or HU other than the factory.
The overhaul manual does not require them to be replaced.

Now the skipping problem.
I'll qualify by saying That I have no method of telling the table of limits that was used when the engine in question was assembled.

If I had to venture a WAG, I'd think some ones dry tappet clearance was not with in limits.
If you have a collapsed lifter, or a weak lifter There are trouble shooting procedures for this.

 

[Tom-D]

Do you still have this engine? (the one that skips)

 

[MBDiagMan]

Yes, it is still installed on the plane.

I fully expect that the skip could be remedied without an engine overhaul. It is the COMBINATION of the skipping, the oil pressure, the oil leaks and the oil usage that leads me to start talking about overhaul. It has never shown metal and the last filter cutting was at annual last September.

 

[overdrive148]

 

[KaiGywer]

I think the time has come to freshen the O200A that is in my beloved Cessna 140. Financially I could never justify the expense in a million years, but I thoroughly enjoy this airplane. It is not a typical 140. It was caringly restored and upgraded with a custom IFR panel, the O200, 150 seats and other upgraded components. It is rigged incredibly well and is still a rag wing. It is a 48 model which means it has several improvements over the earlier versions. All that said, to most anyone else it’s probably just another old plane, but to me she’s part of the family.

150 seats? Wow, that's quite the improvement in capacity

 

[MBDiagMan]

I suppose I should explain the thread title. I have never overhauled an aircraft engine, but I grew up in my Dads car repair shop and have rebuilt a bunch of car and truck engines. Going into an engine is like peeling an onion. It is all exploratory surgery. The further you go, the more you find that must be dealt with.

In the case of this one, I probably could fix the skip with a cylinder or a hydraulic unit, but then I need to pull all cylinders to fix the pushrod tube leaks. I do all that and I am still stuck with low oil pressure and oil usage problems. Where do you stop? I know that if I start into it, I won’t be able to stop peeling. Might as well plan on a thorough overhaul or do nothing.

 

[Terry M - 3CK (Chicago)]

Sorry to derail. I thought a field OH on a 200 would be $10-12k. The engine alone here would be $15, so I assume there is value in the old case accounting for the difference?

How do you get that value? You have to sell it on the market, or you can sell it to Continental?

 

[SkyDog58]

I'd recommend that whatever shop or source you go with that it is a Part 145 Repair Station that specializes in engine overhauls. I do not recommend going with an everyday jack of all trades mechanic whose overhauls are just a small part of what he does.

 

[Tom-D]

I'd recommend that whatever shop or source you go with that it is a Part 145 Repair Station that specializes in engine overhauls. I do not recommend going with an everyday jack of all trades mechanic whose overhauls are just a small part of what he does.

Why? we all use the same machine shops, and are bound to the same requirements.

 

[Tom-D]

I suppose I should explain the thread title. I have never overhauled an aircraft engine, but I grew up in my Dads car repair shop and have rebuilt a bunch of car and truck engines. Going into an engine is like peeling an onion. It is all exploratory surgery. The further you go, the more you find that must be dealt with.

In the case of this one, I probably could fix the skip with a cylinder or a hydraulic unit, but then I need to pull all cylinders to fix the pushrod tube leaks. I do all that and I am still stuck with low oil pressure and oil usage problems. Where do you stop? I know that if I start into it, I won’t be able to stop peeling. Might as well plan on a thorough overhaul or do nothing.

What you can not afford to do, is ruin the crank with a major metal generating failure.
All of your cylinder problems can be cured with 4 new cylinders $940 each.
But that won't help your low oil pressure, that's worn main bearings.
Cranks are very scarce now, new ones from TCM can be bought, but they are back ordered until some time in June or July. and they will be close to $7k.
Crank and cam timing gears are over 2k each from TCM, but you can get lower prices thru Fresno air parts.
The engine I pictured above is made from re-machined and new parts that I bought from various suppliers.

 

[Tom-D]

Why? we all use the same machine shops, and are bound to the same requirements.

The rebuilt to new standards 0-200-A are now priced at $22k by the major shops, Do you really want to buy all new accessories when his are good? I can do that too, for another $10k

 

[Salty]

I don't know of any overhauler that replaces good lifters or HU other than the factory.
The overhaul manual does not require them to be replaced.

Would you be willing to explain why this does not apply?

During overhaul, all hydraulic lifters (tappets) must be replaced with New or Factory Rebuilt lifters (tappets).

from https://www.airmarkoverhaul.com/Continental SB97-6B Mandatory Replacement Parts.pdf

 

[Tom-D]

engine application? the GTSIO_520 isn't a 0-200.
See that mentioned in the list 1-thru-33 that applies to all TCM engines?

 

[3393RP]

You didn't know this?

"Although a service bulletin may be categorized as mandatory by the manufacturer, it is crucial to know that compliance with service bulletins isn’t necessarily required under the FARs (Federal Aviation Regulations) unless the service bulletin includes or is accompanied by an airworthiness directive."

 

[Tom-D]

Ask yourself, why does Aircraft Specialities services have hydraulic units on their reconditioning list? if you must replace with new?

$27.50 each for reconditioning. don't forget, the tappet bodies, and push rod cups are separate

 

[Tom-D]

You didn't know this?

"Although a service bulletin may be categorized as mandatory by the manufacturer, it is crucial to know that compliance with service bulletins isn’t necessarily required under the FARs (Federal Aviation Regulations) unless the service bulletin includes or is accompanied by an airworthiness directive."

I'll not argue about that, because it is a point of law, that will get you in a heap of trouble.

 

[Salty]

engine application? the GTSIO_520 isn't a 0-200.
See that mentioned in the list 1-thru-33 that applies to all TCM engines?

Funny how the other two paragraphs state GTSIO_520 but that one doesn’t mention a specific engine model. I’m glad I’m not an A&P.

 

[Tom-D]

Funny how the other two paragraphs state GTSIO_520 but that one doesn’t mention a specific engine model. I’m glad I’m not an A&P.

You just ask enough questions, and if ya can't get the info you need call TCM tech support.

 

[JAWS]

There is a saying. "Know your suppliers".

 

[Tom-D]

There is a saying. "Know your suppliers".

That is a very good saying, but some times they even get dooped.

Very very much watch your parts and were they come from.
I Know where I buy parts, the 4 bolts that failed in my 0-200 from hell, were proved to be substandard, we can't hold any one responsible because no one kept a receipt of where we bought them..
the litigation is now over, the court threw it out because lack of proof of where they came from.
I know, but no proof

 

[Tom-D]

Peeling the onion, kinda like digging the hole, the bigger it gets, the bigger it needs to be

 

[Tom-D]

Zephyr engines in Florida. I regret having it done at a closer to home shop. Altho Charlie Merlot’s retired, he still hangs out here on PoA.

Charley once told me " you get what you pay for, you pay for what you get"
it's never been truer

 

[SkyDog58]

A Part 145 Repair Station is structured and organized for success. They also undergo far more surveillance by the FAA than does someone working out of their garage or t-hangar.

A Part 145 has:
A Repair Station Manual
A Quality Control Manual
A Training Program / Manual
The manual system include a tool calibration program to ensure tools are calibrated on schedule. This includes all of the micrometers and calipers that are used to measure an engine's dimensions. It also ensures torque wrenches are calibrated so that all bolts on the engine are properly torqued.
The QCM's quality control system will usually have a second set of eyes looking at critical functions. One such function might be torquing critical fasteners.
The QC system includes vendor surveillance. This includes parts suppliers and other shops who do any sub work for the repair station.
A 145 has personnel specifically trained for the task they are doing and who do it often enough to maintain a high degree of proficiency.
And there is more.

This is why I prefer a Part 145 over the typical mechanic in the field when it comes to something such as engine overhauls.

 

[Tom-D]

A Part 145 Repair Station is structured and organized for success. They also undergo far more surveillance by the FAA than does someone working out of their garage or t-hangar.

A Part 145 has:
A Repair Station Manual
A Quality Control Manual
A Training Program / Manual
The manual system include a tool calibration program to ensure tools are calibrated on schedule. This includes all of the micrometers and calipers that are used to measure an engine's dimensions. It also ensures torque wrenches are calibrated so that all bolts on the engine are properly torqued.
The QCM's quality control system will usually have a second set of eyes looking at critical functions. One such function might be torquing critical fasteners.
The QC system includes vendor surveillance. This includes parts suppliers and other shops who do any sub work for the repair station.
A 145 has personnel specifically trained for the task they are doing and who do it often enough to maintain a high degree of proficiency.
And there is more.

This is why I prefer a Part 145 over the typical mechanic in the field when it comes to something such as engine overhauls.

And you assume the A&P wouldn't do that?

 

[JAWS]

A Part 145 Repair Station is structured and organized for success. They also undergo far more surveillance by the FAA than does someone working out of their garage or t-hangar.

A Part 145 has:
A Repair Station Manual
A Quality Control Manual
A Training Program / Manual
The manual system include a tool calibration program to ensure tools are calibrated on schedule. This includes all of the micrometers and calipers that are used to measure an engine's dimensions. It also ensures torque wrenches are calibrated so that all bolts on the engine are properly torqued.
The QCM's quality control system will usually have a second set of eyes looking at critical functions. One such function might be torquing critical fasteners.
The QC system includes vendor surveillance. This includes parts suppliers and other shops who do any sub work for the repair station.
A 145 has personnel specifically trained for the task they are doing and who do it often enough to maintain a high degree of proficiency.
And there is more.

This is why I prefer a Part 145 over the typical mechanic in the field when it comes to something such as engine overhauls.

I wonder if they use silk thread on their cases?

 

[Tom-D]

I wonder if they use silk thread on their cases?

many do not. they have their cases lapped and don't need it. Why would you pay to have a perfect fit, then place something in it to hold it apart?

 

[JAWS]

LOL!

 

[Tom-D]

LOL!

Your laughing simply shows your lack of knowledge on the subject.