pull a cylinder off to view camshaft and lifters?

[jetdriven]

We had a cylinder pulled off during the prebuy to check for corrosion, pitting, or a rounded off cam lobe.  We found nothing wrong, and bought the airplane.  A year later all is well. However, this seems rare to do such a job on the prebuy. Some have lamented not doing it and had to overhaul the first year. 

How many of you considered doing this, or actually did the job?  Comments? Ideas? 

[MooneyMitch]

My opinion on this, it would certainly depend on the circumstances of the aircraft in question.  I would not hesitate pulling a cylinder for the internal inspection, along with the Lycoming valve wobble test, and with the normal compression test and boroscope inspection.

Yes sir!

 

[KSMooniac]

I did not do it, but knew my plane had been flying a lot in the previous 2-3 years before I purchased it.  If it were a low-use plane, then I would have insisted.

[Seth]

During my pre-buy for my Mooney Missile in 2011 I had a cylinder pulled too look "inside" due to metal contaminents in the oil filter after a wonderful test flight and after a pretty good prebuy inspection.  It was a determination made as per the A&P's recommendation.  Turns out on lobe was bad and the lifters were pitted pretty badly.  I reduced my offer since an overhaul was in the future (either of the bottom end was needed, but that was good money after bad with the engine time - so it was a full overhaul).  I saved a lot of money and immediatly overhauled the engine on purchase.

If the metal particles had not been in the oil filter, I'm not sure if I would have pulled the cylinder.  I may have simply due to engine time (1550ish on an IO-550 with about 200 hours and a few years since a top overhaul).  I was also following the advice of Jason the mechanic based at BBB who was recommended by Bruce Jager to me.  Bruce conducted the test flight for me.

I did not pull a cylinder on the purchase of a 1967 M20F model in 2008, but it was maintained by the MSC that it was based at and I did trust their opinions as to the health of the plane they maintained.  I had very few engine issues (debris in the fuel injectors twice) during 3 years and 500 hours of ownership of the F.  It was also a factory overhauled engine at purchase with about 50 hours on it SMOH.

Take care,

-Seth

Update:  I relized I may have made a mistake in terminolgy.  I had a borescope completed inside the engine, not a cylinder pulled, unless it is the same thing, and I am not sure if it is or not.  I know that the mechanic had to remove a cylinder, or removed something in order to get inside the engine to take a look, but he did use some sort of borescope tube as well. 

[M016576]

I bought my 201 in mid '09.  The airframe had low hours, the engine had less than 200 hours (on the lycoming factory overhaul) in 10 years, but a recorded "pickled" period in the log books (to include oil used, dessicant, etc etc).  I had a thorough pre-buy inspection conducted and flew out to view the aircraft myself, prior to making the purchase.  I did not have a cylinder pulled, mainly due to ignorance and lack of research on the subject.  Compressions came back in the high 70's on each cylinder, and while there were a couple issues with the aircraft (older hoses, light hail, older baffle seals, improper pre-loads on the gear). the majority of the aircraft looked servicable (very clean inner wing with evidance of anti-corrosion sprays, new donuts on the gear mounts, new tires, new aux fuel pump, some other new bits and pieces).  long story short, I felt the bads and the goods were balanced well and put in an offer 5k under asking price which was promptly accepted.

Fast forward 2.5 years.  My motor is in Portland being overhauled at 400hrs tsmoh.  spalled lifters, cam coming apart, evidence of corrosion in the cylinders that was worn off during my ownership... but the damage was already done.  the initial compression checks didn't catch it, since the corrosion was initially *helping* the compressions.  Once all the corrosion wears off, though, and the uneven wear begins, oil consumption picks up rapidly (which was clue 1).  the spalling from the cam& lifters only gets worse as well (metal showing up first with increased wear in oil analysis, then in the oil filter). 

I'm not a rich man, and while I can swing the overhaul with savings, it is a stretch and a service action that I wasn't hoping to have to go through.  regardless, it is a risk of ownership and one should probably not embark on aircraft ownership without considering the *need* to overhaul their motor.  If I were to do it again, I would have insisted that a jug be pulled to inspect the cam.  If the aircraft that I was looking at, though, had a relatively new motor with low time (say 200 hours a year or so) and verifiable logs showing regular use, I would probably not have a jug pulled.  JMHO.

[Jerry 5TJ]

If I were a SELLER of my "C", I am not sure I'd let a potential buyer pull the cylinder.  I'd figure, why disturb a good 600TT SFNE?  I'd let them do a borescope exam.  Of course, as a BUYER I might want to see what is in there. 

[kortopates]

I'd prefer an engine that was being flown a 100 or more hours per year before prorating it to its full value based on hours alone. If it had a history of being flown 50 or less per year for multiple years I would insist on pulling a cyl or would pass. The greater the desparancey between engine age and hours the more uncomfortable I would be valuing the engine based on remaining hours without pulling a Cyl. That said, its not always necessary to pull the cyl though, I’ve pulled the lifters out of straight valve engines to measure lobe height with a dial indicator and would consider that adequate if the lobes didn’t show much wear.

[N601RX]

What's to say that an engine that appears to be flown for 100 hrs year didn't set for 3 or 4 months without being flown.  This may be especially true in certain climates. The 100 hrs may have been put on it in the late spring, summer and early fall. It may have set for durring the cold damp months.

Has the plane set at some point due to paint or other extended maint? It only takes once for rust to start, after that it's only a matter of time.

We purchased our plane with the engine at TBO and using oil, so we didn't feel the justification to pull a cylinder knowing we would overhaul it within the 1st year anyway.  When we pulled it apart, we found broken oil rings that didn't show up on the compression test, rusted lifters, rusted wrist pins, and rust on a couple of the gears. The crank and rods were clean.  One other thing of interest was the screen on the governor, it had a lot of junk in it, but you never hear of anybody removing it to look at it.

[skippyf16]

How many hours labor to pull and reinstall the jug?

[carusoam]

Skippy,

you have a lot of time to add some detail to your question...

The necro thread you have appended to is a bit aged...

Are you needing to pull a jug on your plane?

Which Mooney is it?

What makes you want to pull it?

Best regards,

-a-

[RLCarter]

I would think ALL (2 or 3 depending on Powerplant) cylinders on either the left hand or right hand side should be pulled for a good look at the cam/lifters

[67 m20F chump]

I got burned on a continental motor that had a lifter issue.  It was on a 1200 hour factory overhaul and sitting next to a 1500 hour field overhaul.  The field overhaul is still running strong today on the twin I sold.

On my next aircraft purchase I paid a Mooney pro to change the oil and look at the filter and screen and do a 208 inspection.  When I got the plane home I could tell the safety wire on the screen was old because it was crusty and only had one flight on it since the oil change.  I also have doubts the 208 inspection was properly done.  You roll the dice you take your chances.  When you buy an aircraft be ready to drop 30k on it at any given time.  That is why I didn’t have an airplane when I was younger.  I figure with a Mooney if you have serious problems you can always part it out and keep what you want for your Van’s Aircraft build.  Aviation really is expensive.  Who knew?

[M20F]

49 minutes ago, 67 m20F chump said:

When you buy an aircraft be ready to drop 30k on it at any given time. 

Pretty much this.  You can minimize it but hard to check things like metallurgy. 

[PT20J]

1 hour ago, M20F said:

2 hours ago, 67 m20F chump said:

When you buy an aircraft be ready to drop 30k on it at any given time. 

Pretty much this.  You can minimize it but hard to check things like metallurgy. 

I think this sums it up. Just like the asking price, the depth of the pre-buy is whatever the buyer and seller negotiate and this will vary according to each party's perceived risk and risk tolerance. In my case, I found a 94 J with less than 1200 hours on it that had been well maintained and had some nice avionics upgrades. On the down side, it was burning about 1/2 qt per hour and hadn't been flown much the last few years. I had a thorough pre-buy done by Don  Maxwell who personally borescoped the cylinders. No metal in the filter, compressions in the mid-70s, oil analysis was good and trends OK compared to previous several. The engine started and ran well. The airplane seemed a little slower than I recalled my last one, but that was many years ago, with less instrumentation and fewer antennas. I didn't even consider pulling a cylinder. I negotiated a fair price based on known condition (the rest of the pre-buy showed only very minor issues).

Twenty five hours after purchase, the oil ring in #4 broke taking out part of the piston skirt and scoring the cylinder. When we pulled the jug (low compression, metal in the filter) we found the cam spalled. So, now I have a rebuilt A3B6. Cost some money, but I ditched the dual mag, and got roller lifters and a zero-time logbook. Maybe the ring was broken before I bought it. Maybe we could have figured it out if we had pulled the #4 jug. Maybe we should have pulled them all. Maybe we should have disassembled the entire engine. I think at some point you just have to accept that buying a 25-year-old piece of complicated machinery is a risky proposition. The point is: I'm fine with my decision based on what I knew at the time; others might have wanted to probe further.

Skip

[jaylw314]

12 hours ago, RLCarter said:

I would think ALL (2 or 3 depending on Powerplant) cylinders on either the left hand or right hand side should be pulled for a good look at the cam/lifters

Mike Busch cited a number of engine failures attributed to work on more than one cylinder at a time.  If not done correctly, the preload on the crankcase through bolts can be incorrect resulting in eventual failure.  He argued that with multiple cylinders off, it is difficult to do this correctly while the engine is still on the plane, so this represents a tangible risk for a maintenance-induced failure, especially if done by a mechanic that is not accountable to the seller.

As a seller, I would not accept having multiple cylinders off or any invasive inspection for that matter.  Removing spark plugs, interiors, belly panels, inspection panels and cowlings is fine--these activities have a low enough risk the FAA allows owners to do it, but if a mechanic is required to take something apart, there is an increased risk of maintenance-induced failures afterwards.  I might consider having one cylinder off if it was with my mechanic and under my watch.  

As a buyer, I had the cylinders borescoped and the oil and filter examined.  I would have wanted past oil analyses, but the motor was new rebuild that had no analysis history.

[PT20J]

Mike Busch also has recommended setting up an escrow account for a fixed duration that holds back a portion of the purchase price. If the cam survives the escrow term, the seller gets the money; if not it goes to the buyer. Seems pretty reasonable. All part of the negotiation.

Skip

[ArtVandelay]

I’m not sure, but can’t you pull the plugs in the oil pan and snake the borescope up around the crankshaft and inspect the cam that way. Obviously this would require draining oil and a quality borescope.


Tom

[jaylw314]

34 minutes ago, ArtVandelay said:

I’m not sure, but can’t you pull the plugs in the oil pan and snake the borescope up around the crankshaft and inspect the cam that way. Obviously this would require draining oil and a quality borescope.


Tom

AFAIK, it's darn near impossible in a Lycoming.  There might be other entry points (the oil screen?), but I suspect the view would be pretty limited still...

[David Lloyd]

You take it apart and you buy it.  Worn cam or bad lifters and we can negotiate the price.  But it isn't mine after someone else pulls off a cylinder.

[gsxrpilot]

I just assume an engine that's been sitting, is run out, and price it as such. If the seller disagree's, we probably don't reach a deal.

[Sabremech]

The majority of the cam issues appear to be the 200 HP IO-360 engines. I rarely hear issues with the O-360. My airplane has sat quite a bit the last 2 years while working on the cowling in a dry heated hangar.

When I sell it later this year, for issues mentioned, am not inclined to pull a cylinder on my O-360. If I choose to do it, it will be me doing it and not someone else. 

I have a mock-up 360 engine case and I’ve brought my borescope home and have yet to find a way to get up to the camshaft and I can see through the engine. 

David

[larryb]

As a seller I would not agree to such an invasive inspection as taking off a cylinder. Way too much risk of a maintenance induced problem that I would own if the buyer did not purchase in the end. 

 

As a buyer, I would realize that taking a cylinder off would cost 10 hours labor and probably $1200. Put that towards the engine fund. You can get a good idea of risk based on oil changes, oil filter, and hours flown. All of these engines are a risk no matter how good the inspection.

 

One thing I think would be valuable in a pre-buy is downloading the engine monitor data and reviewing that. When I bought the Encore I asked the mechanic to do this, and it was like they had never done it before. They did not have the cables and/or software for the JPI 700. I would have done it myself except I was buying it long-distance. In the end they did, but it didn't matter because the monitor was old and was not set to record data. So nothing there to review. 

[Yetti]

I don't think the buyer would be willing to accept the risk going forward of having a cylinder pulled.

[BaldEagle]

With my last Mooney I had a cylinder replaced not long after the purchase.  The engine then started throwing oil all over the place, which was tracked down to a large crack in the case = premature (unplanned) major overhaul.  I suspect that the cylinder through bolts were over torqued when reinstalling the replacement cylinder, but this opinion is unqualified.  But I wouldn’t pull a jug off to entertain a prospective buyer with this experience in mind.

[gsxrpilot]

When/If my 252 is ever for sale, the data from every single flight will be available on SavvyAnalysis for review by the buyer.