Oil Analysis from Blackstone after inactivity

[MooneyBob]

I have received the gadgets from the Blackstone to get and send out my oil sample.

Here is a deal. I have bought this 1977 M20J a month ago. It has a new engine that was installed sometimes in 1999 and has only 485 hrs on it. I know it didn't fly to much last ten years and there is serious corrosion concern. It has flown only 3 hours since the prebuy / annual inspection and oil change ( Jan 9 2014). I'd like to get the oil sample analyzed now, then maybe after 15 hrs, then after 25 hrs and then when I change my oil probably 35hrs. I will check the filter too of course. I'd like to get the " progress report " from these analysis and see how the oil parameters change in this first period of flying after inactivity.

Questions:

1. Anything wrong with the idea of oil sampling this way?

2. How to find out if there is any corrosion issue beside the ( unreliable) oil sampling - looking for iron? Take the top apart?

 

Thanks

[kmyfm20s]

If you take the sample right away I think it would shock you. I would run it a couple more hours then change the oil and sample after 25 hrs.

[MooneyBob]

I am prepare for the shock. But that's my idea - to see the either improvement, stability or decline.

[jetdriven]

Wear metals track with hours so I'd fly it an hour then change it. Skip the sample if you wish, it's not going to be useful data. Then sample and change at 25 hours, and again in another 25hrs.

The best way to inspect the cam and lifters for corrosion is remove two jugs on one side and visually inspect all the cam lobes and lifters. That's quite involved and since you already own the plane, best bet is to use Camguard, fly it at a minimum once every 14 days, and hope it doesn't go bad. You will know if it does, you will start to get a lot of ferrous metal in the filter and iron counts over 100 PPM.

[mike_elliott]

After you fly it for 25 hours, I would pull the suction screen and check it for cam and lifter chunks in addition to the oil analysis

[John Pleisse]

Run it for a short spell and immediately crack the filter and take the analysis sample. If you are going to shed spalling debris, it'll happen quick. I am big on bore scoping and the technology keeps getting better. It's worth a few hundred bucks and you may not have to pop a jug any longer. Oil analysis is a great long term indicator or trend identifier. You want to know now.

[N601RX]

Here is a slightly different prospective. If the iron content was high what would you do? Would you be willing to tear the engine down on a couple of high readings? Even with the high reading I think most owners and mechanics would suggest keep flying and keep a close check on the filter and screen.

[Cruiser]

Do you know the engine has corrosion in it? If you are just trying to get a few more hours from the engine before you overhaul it again, forget the oil sampling and just check the filter for metal.

If you are trying to salvage the engine for longer term operation it needs constant use. It should be flying every couple of days. You might get 150 - 250 hrs. on the lifters that way before they start spalling. You will see metal in the filter before the oil analysis is going to indicate a problem.

 

If you are starting with an unknown history and need to develop trends fly it for 5 or 10 hours change the oil and then start a 25 - 35 hour oil sampling analysis.

[chrisk]

First off, I'm not a mechanic.  If it were my plane and I was concerned, I would probably just pull the oil filter after 10 hours and cut it open.  I'd wait on the oil analysis until 25+ hours.   My reasoning is there are some limits on the testing technology, there is a mix of old an new oil, and the new oil hasn't run long enough to pick up enough small particles.  

 

Another issue is correlation of the data.   When I have sent samples in the past, they get compared to other similar engines (and I believe past samples).  This only provides value if the time on the oil is in the same ball park.

[MB65E]

Any thoughts on running mineral oil in it with some hard frequent use for 10 hours or so? That might be enough time to let things ware in, knock some sediments off, etc..

I'd put a little more time on it first before your sample. Then try to repeat the same test over the next segment of hours. Same mixture settings, similar time of flights. I think you might make out. At least it had some time on it... Not like 100 hrs in 10 years.

I wish their were some bore scope plugs like on turbine engines for our lycomings! Good luck!

-Matt

[Bob - S50]

Our group bought a plane last year that sat in a hangar in northern CA for 10 years.  It was worked on by LASAR (who we bought it from).  We flew the plane for 25 hours then did an oil analysis.  Not unexpectedly ALL metals were high.  We had figured after sitting that long there would be surface corrosion almost everywhere, but sitting in a pretty dry warm climate we were not too worried about serious problems.

 

We flew it another 25 hours and changed the oil again.  All metals were normal.  Three more subsequent oil changes have also come back normal.

 

I can see it either way as recommended by others.  Check it now if you want, but expect high readings.  Or, fly it at least 10 hours to give it time to work off most of the surface corrosion, change the oil, check the filter, then fly it 25 hours and get the oil checked.  If you have high metal counts at that point then you might have a problem.

 

Congratulations and have fun!

 

Bob

[Marauder]

At the end of the day, it will or it won't have problems either sooner or later... Fly it, enjoy it and deal with the problem when it occurs -- and it will, just hope it is later...

[MooneyBob]

This is the best way to deal with that. Fly it and keep an eye on it. I hope to fly it at least 10 hours this weekend.

Thanks for your help everybody.

[N201MKTurbo]

So corrosion will normally attack the cylinder walls possibly causing a loss of compression, or the cam and lifters causing lifter spalling and accelerated cam wear.

 

With cylinders the rust will be cleaned off the first time you start the engine and you will show a large amount of iron in your analysis. Your cylinders may still have many hundreds of hours of serviceable life left after this rust event. I would go on compression readings and oil consumption rather then immediately condemn the cylinders.

 

I had an engine with spalling once. it will just manifest itself as a gradual loss in performance as the cam lobes are ground off. The end game would be when the cam lobes are so warn that they will not open the valves and that cylinder will misfire.

 

The bottom line is that I don't think any corrosion related issues will cause catastrophic engine failure. The only harm in waiting is that your cam may go from being regrindable to junk. I would suggest replacing the cam if it is warn.

 

The point is that I wouldn't be in any hurry to tear down the engine. Run it for a while and see if the metal in the oil stabilizes.

[jetdriven]

I caught my cam spalling event before any loss of lift was detectable. But three of the lifter faces were completely spalled out. The only indicators of this were a gradual increase in iron to 100+ PPM/50hr and a steadily increasing amount of ferrous metal in the filter. How much? Negligible at first then it progressed to 1/4 teaspoon then 1/2 teaspoon in 25hr, over a 50-60 hour period. Magnet on a stick filter element inspection showed some powder but wishing the element in a quart bucket of mineral spirits and careful straining through a coffee filter will show all of it.

But don't let any of this scare you. Fly it often and hope it doesn't happen to you. Like N201MKTurbo says, it's not going to fall out of the sky.

[MooneyBob]

Thanks for the educated thoughts. The last two compression test ( prebuy in October then some taxing and run ups and then annual in January shows 76+ compression on all cylinders. That's encouraging.

I will look for any other signs and I will perform the borescope probably too.

[Marauder]

Another thing you can do to watch for metal is to put a rare earth magnet on the oil filter. It will catch the fines on the inside wall of the filter.

[kmyfm20s]

Tempest filters have a magnet built in.

[MooneyBob]

Good idea with the magnets.

[carusoam]

Where in Jersey are you Bob?

Best regards,

-a-

[MooneyBob]

KBLM  ( Monmouth Executive - Belmar). Love that 7400' strip.

[John Pleisse]

On the one hand, if it is diagnosed, you can pay $8-$10k to split the case, do the cam, lifters, guides, etc now and address it before it makes enough metal to ruin the rest or your engine. You could save the jugs, and lower half, avoiding a major. If you got a deal on the plane to the extent the engine is covered, go and see how many hours you can put on it before it gets bad, then major it. You might get 200 hours or more..you might not have a problem at all. Point being, a necessary top end fix that is identifiable, should not cost you a major (am I making sense?). If it were an 1800 hour engine, this would be a no-brainer.

 

A catastrophic failure is unlikely, you and your A&P would see it coming.