Breaking in New Cylinders/Trouble with an A&P

[ShyFlyGuy]

I just replaced all 4 cylinders on my Cessna 152 (O-235-L2C) and took off for work... When I came back, the A&P (who is also an AI) had taken it out, run it up for about 20 minutes, and then ran compression checks. Says that it had little compression. While I was gone, he called to ask what kind of oil I wanted to run in it... I was confounded. "Don't you run Mineral Oil in there?" asked. He thought about it and said he would if I wanted to. OF COURSE I DO! THEY'RE NEW CYLINDERS!!! So now he's refusing to sign it off because he isn't getting good compressions out of brand-new cylinders. I have since hired a new mechanic to sign the cylinders off (who also supervised my work on the installation), but the old mechanic still won't sign off on the annual (which took him 8 months).

My questions:

1. Am I wrong to have used Mineral Oil on new rings, pistons, and cylinders?
2. Isn't it normal to have marginal or poor compressions after only a run-up?
3. Is it possible he glazed the cylinders with an extended run-up without the cowl on to direct the flow of cooling air?
4. Can he sign off an annual without testing the compressions, if the answer to #2 is yes?

Thanks a lot...

Shy

 

[erj-145mech]

I've always used straight mineral oil to break in more than one cylinder after rework. I've also drained it after 25 hours or the oil consumption has stabilized. Usually it will have stabilized before the 25 hour mark.

Your current mechanic/IA should sign the annual off as unairworthy and must present you with a list of discrepancies. Once your new mechanic, and he does not have to hold an IA, corrects these discrepancies, and makes the log book entry, you are then in annual. If he refuses to sign off anything, refuse to pay.

This as all spelled out in FAR 65, and is available on line for free at www.faa.gov. (except for the not paying part)

 

[Berkut]

Just to tack on a little more to erj-145mech excellent response:

My questions:

1. Am I wrong to have used Mineral Oil on new rings, pistons, and cylinders?
2. Isn't it normal to have marginal or poor compressions after only a run-up?
3. Is it possible he glazed the cylinders with an extended run-up without the cowl on to direct the flow of cooling air?
4. Can he sign off an annual without testing the compressions, if the answer to #2 is yes?

1. You are correct. You should use mineral oil for break-in.
2. Possible, yes.
3. Possible, yes.

Number four is the big one. Yes, if he performed that annual inspection, he needs to be signing it off, airworthy or not. Anything else is a load of crap, and would have me madder than hell. Any discrepancies he found can be later corrected and returned to service by a mechanic you trust. The mechanic might find that the discrepancies were bogus, in which case no corrective action would be needed.

Good luck.

 

[USMCmech]

4. Can he sign off an annual without testing the compressions, if the answer to #2 is yes?

He is required to check the compression durring the annual.


However you need to back up several steps.

The A&P in question completed the "annual inspection" several months ago. He is required to sign off the airplanes logbook stating such. He can (and should) sign it off as "completed annual inspection, a list of discrepencies has been provided to the owner. Date, signature, IA #."

What remained was fixing the discrepencies, and returning the aircraft to an airworthy condition. This can be done by any A&P you choose, and you can do some of that work yourslef, check Pt 43.

 

[avbug]

I just replaced all 4 cylinders on my Cessna 152 (O-235-L2C) and took off for work... When I came back, the A&P (who is also an AI) had taken it out, run it up for about 20 minutes, and then ran compression checks. Says that it had little compression. While I was gone, he called to ask what kind of oil I wanted to run in it... I was confounded. "Don't you run Mineral Oil in there?" asked. He thought about it and said he would if I wanted to. OF COURSE I DO! THEY'RE NEW CYLINDERS!!! So now he's refusing to sign it off because he isn't getting good compressions out of brand-new cylinders. I have since hired a new mechanic to sign the cylinders off (who also supervised my work on the installation), but the old mechanic still won't sign off on the annual (which took him 8 months).

Posession of an inspection authorization by your mechanic has no bearing on his actions as a mechanic in changing the cylinders, runnng the engine, or taking the compression test.

You're aware that unless it was synthetic oil, it WAS mineral oil right?

Multi weight AD oil is mineral oil.

An engine may be broken in on multiweight oil. An engine may be broken in on AD oil. Straight weight mineral oil isn't necessary, and no, your cylinders won't glaze over because a multi-weight oil is used. Much more important is the proper break-in proceedure. The cylinder manufacturer will spell that out, but a quick run isn't adequate to seat the rings.

A compression check is a tool, but is often taken for all that it's not. The compression values are only a part of the picture; where the pressure is going is important.

The idea of using a straight weight oil for break-in only is an old one, and has long been proven invalid. Old myths die hard, however, and as some manuals have never been updated to reflec curent technology, it's still reflected in some maintenance documents.

Your IA has been working on the aircraft for eight months...this work was in connection with the annual? Something doesn't add up; not enough information has been provided.

 

[ShyFlyGuy]

Wow! Gentlemen, thank you for your replies! This has been so educational and I am amazed at the wealth of knowledge you all have. Again, thank you so much for your input.

To answer some of the remaining questions... So far, I've got 7 hours on the engine since I replaced the cylinders. It is in the last 3 hours, it is burning .44 quarts per hour. There is no oil coming out of the exhaust, or leaking out into the engine compartment. I'm relieved to hear that it may take up to 25 hours to break-in, because I was expecting it to take 5 hours or so, and was concerned about it still burning oil. The mechanic who performed the annual is an ex-military guy who did a lot of work on turbines. Unfortunately, that makes him VERY through, perhaps a bit too much. He fixed EVERYTHING that was broken or cracked on that plane and didn't do me any favors. He did a great job, and the plane is in top shape, but I was not his #1 priority. He made me pre-pay on a lot of the parts, pre-pay on his estimated labor, and after all that, put me in the back of the line (although he did give me a break for pre-paying on the labor:$45/hr). So that being said, the plane went down in the end of August and only JUST got out of annual. It was a trial of my patience, but I'm just glad to have it airborne again. She's beautiful and is flying wonderfully.

Shy

 

[ShyFlyGuy]

Oh, one last thing...

With the new cylinders on there, the prop doesn't turn very easily at first when pulling it through by hand. It starts quickly and easily, but when pulling it through, it is very tight to begin turning, and then turns easier after about 1/8th of a rotation. The compressions seem strong, but other than that, it moves "normally". It's the stiffness that it develops after sitting for a minute or two that concerns me. It physically won't move until about 10-20 pounds of pressure are applied, then it takes less than 5 to keep moving it. Is that normal for new cylinders/engine? It has gotten better since 0 hours.

Shy

 

[Berkut]

An engine may be broken in on multiweight oil. An engine may be broken in on AD oil. Straight weight mineral oil isn't necessary, and no, your cylinders won't glaze over because a multi-weight oil is used.

The idea of using a straight weight oil for break-in only is an old one, and has long been proven invalid. Old myths die hard, however, and as some manuals have never been updated to reflec curent technology, it's still reflected in some maintenance documents.

Lycoming service instruction 1014M still states:

D. All other engines must be operated on mineral oil during the first 50 hours of operation, or until oil
consumption has stabilized. LW-16702 additive may be used. If an ashless dispersant oil is used in a new
engine, or a newly overhauled engine, high oil consumption might possibly be experienced. The additives in
some of these ashless dispersant oils may retard the break-in of the piston rings and cylinder walls. This
condition can be avoided by the use of mineral oil until normal oil consumption is obtained, then change to
the ashless dispersant oil. Mineral oil must also be used following the replacement of one or more cylinders
or until the oil consumption has stabilized.

I know some engines can be (some must be) broken in using AD instead of straight mineral oil, but nothing I see for his engine indicates that anything other than straight mineral is acceptable. Do you have updated information from the manufacturer concerning this, or anything official I can consult?