Oil analysis

Discussion in 'Maintenance Bay' started by 455 Bravo Uniform, Nov 29, 2017.

  1. 455 Bravo Uniform

    455 Bravo Uniform Cleared for Takeoff

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    Chrome came back high 80+ppm, average for IO-470 is 11ppm. All other metals in normal range. No prior reference samples.

    As far as I can tell from my logs, I don't have chrome cylinders.

    (1) What do you think it is?

    (2) How can I tell from the outside if I have stock TCM, Millenium, or other cylinder?
     
  2. Ryanb

    Ryanb En-Route PoA Supporter

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    Chrome can come out of the rings and can also be found in the cylinders if they’re steel. If chrome is a meaningful wear metal on your engine, the report sheet should say, although that does seem rather high.

    As for (2): Do your cylinders not have the manufacturer on the head? All cylinders that I’ve seen have the branding stamped onto the cylinder head.
     
  3. 455 Bravo Uniform

    455 Bravo Uniform Cleared for Takeoff

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    Thanks Ryan. They actually called me. I didn't ask if they normally call or if they called because it was an odd result. They pointed to the rings too, because I told them the cylinders were stock.

    The engine is a TCM Gold Medal rebuilt that went through another overhaul a few years ago. Nothing I can find in the logs shows the cylinders were replaced, so I assume they are stock TCM. I want to actually confirm by eyeball that they are indeed factory cylinders.

    Compression check and borescope next.
     
  4. denverpilot

    denverpilot Taxi to Parking

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    Hmm. Yours sounds a little more worrisome than our long-term elevated aluminum.

    Let us know what you find.
     
  5. James331

    James331 Touchdown! Greaser!

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    Useless





    How's the oil filter cut look?
    CHTs
    Oil temp and Pressure
    Oil burn
    Performance
     
  6. AKBill

    AKBill Cleared for Takeoff

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    The base of the chrome cylinders in my engine are painted orange. I also know that some just paint some of the fins orange.
     
  7. brien23

    brien23 Line Up and Wait

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    Another quality overhaul with the same old cylinders, just have to wonder what other old parts that would have been replaced with a factory overhaul are still in use.
     
  8. 455 Bravo Uniform

    455 Bravo Uniform Cleared for Takeoff

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    This was a "Gold Medallion" TCM factory rebuilt engine (has since been overhauled) that I assume has some sort of factory cylinders. Whether the cylinders were new or refurbished, I don't know, nor do I assume that some prior owner didn't replace them at overhaul. That's why I want to be able to try to ID them externally to confirm.
     
  9. 455 Bravo Uniform

    455 Bravo Uniform Cleared for Takeoff

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    Thanks. No orange on mine, but it's been overhauled once so the paint may be gone.
     
  10. 455 Bravo Uniform

    455 Bravo Uniform Cleared for Takeoff

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    All operating parameters have been normal.

    Three tiny flecks of a white non-ferrous metal in the filter. Like 1/64" to 1/32" in size. My mechanic did not like it. To me it looked like bearing metal, but bearing metals were low in the anslysis (If it was my race car, I'd run the snot out of it, but I just roll it onto the trailer if it craps out...not the same as being airborne with precious passengers). Chrome would be magnetic, right?
     
  11. Checkout_my_Six

    Checkout_my_Six Final Approach

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    image.jpg Meh...just a guess. Piston wrist pin wear like this. :D
     
  12. Clark1961

    Clark1961 Touchdown! Greaser!

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    Chrome itself isn't magnetic most of the time. Warm it up a bit and it will be sorta magnetic.

    Chrome plated material may be magnetic if the substrate is magnetic.
     
  13. Brad Smith

    Brad Smith Pre-takeoff checklist

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    Over 7X the average amount of chrome present in the analysis would be a point of concern to me. Chrome cyclinders have a very unique appearance on the interior walls and can easily be checked with a boroscope. Also, chromed lifters, piston rings and push rod ends should be considered in your investigation as they are high-wear items. A differential compression test would be an easy way to compare cylinders but might also indicate abnormal valve or valve seat wear. If the next analysis shows 15X the allowable amount of chrome, what will you do?
     
  14. James331

    James331 Touchdown! Greaser!

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    Ahh.

    I'd run it carefully (like not night or IMC or mountains) to the next oil change and cut it one more time.

    If you find metal again.....


    But I don't have a good feeling about this
     
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  15. Ryanb

    Ryanb En-Route PoA Supporter

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    Speculate much? That’s quite the claim without any evidence. New cylinders are certainly not immune.
     
  16. 455 Bravo Uniform

    455 Bravo Uniform Cleared for Takeoff

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    Just thinking one step ahead at this time: scope and compression test. If nothing jumps out, another filter check and oil test at 10-15 hrs...or do a precautionary tear-down (now or at 10-15 hrs). One step at a time, let's see what happens next.
     
  17. Checkout_my_Six

    Checkout_my_Six Final Approach

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    If you're not finding teaspoon fulls of metal in the filter....I'd not be overly concerned.
     
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  18. 455 Bravo Uniform

    455 Bravo Uniform Cleared for Takeoff

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    Late night Internet research. Last sentence of the Chrome paragraph. This engine came from the factory in the early 1990s. What if - the same damn exhaust valve guides are still in the heads?

    Back in the 1980's when we had automotive heads being rebuilt for street-strip or strip duty, we would have the valve guides knurled for tighter clearance and oil control on worn out guides (was cheaper and we never needed them to last thousands of miles). In the aviation world, did people do the same knurling with valve guides? If so, do they still?

    If these heads are factory TCM from 1990 a (need to check the logs) and the valve guides looked "good" during the 2000s rebuild (because of their hardness), maybe they were left as is and they are chewing up the sides of the valve stem. Anyway, something else to check.


    image.png
     
  19. Checkout_my_Six

    Checkout_my_Six Final Approach

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    nope....no chrome there.