Suggestions if Metal is Found in the Screens or Filter


Because the failure to look for metal in the screens and filter, or ignoring what is found, can lead to catastrophic engine failure, we’ll attempt a logical approach to the proper action to be taken when metal shows up in the oil screen or oil-filter cartridge.

The lack of printed matter on this subject may be due to the difficulty in adequately describing types and amounts of metal. It’s like asking for a precise measurement and getting the answer, “why it’s 25-thousandths plus a little bit.” Therefore, what follows are meant to be general guidelines, but each case must be considered as an individual one. Lycoming does not consider this discussion a technical bulletin, but merely a source of generally helpful information.

General Information
  1. On small amounts of shiny flakes or small amounts of short hairlike bits of magnetic material. Experience has shown that engines are sometimes pulled unnecessarily.
  2. Don’t panic if it’s a low-time engine. A few bits of metal left from manufacturing are not too uncommon in the oil screen or filters on new, rebuilt or overhauled engines.
  3. Don’t panic again, if it’s a low-time engine, it may be a replacement for one that had previously suffered a structural failure. The metal may have just been dislodged from some hiding place in the oil cooler, oil lines or oil tank.
  4. Item 3 brings up the importance of properly cleaning all items transferred from a failed engine to a replacement engine. On drysump engines, don’t overlook cleaning of the oil tank. Oil coolers and oil lines should be cleaned by a proven method or replaced.
  5. In some rare cases where the pleated cylindrical-type oil screen is used, the screen itself may be making metal. Closely inspect the end of the internal relief valve ball. If the ball is deformed, this may be the culprit. Replace the screen assembly.
  6. In cases where metal shows up in the filter of a factory engine that is under warranty, and its origin is unknown, the metal may be forwarded to the Lycoming factory for inspection. In all cases, the factory Product Support Department should be called before the material is shipped.
  7. Read more about metal solids identification after oil servicing in Service Bulleting number 480.
  1. Several pieces of shiny flake-like, nonmagnetic, or several short hairlike pieces of magnetic material – place aircraft back in service and again check oil screen or filter in 25 hours.
  2. As in Item 1, but larger amount, such as 45-60 small pieces – clean screen, drain oil and refill. Run engine on ground for 20-30 minutes. Inspect screen. If clean, fly aircraft for 1 to 2 hours and again inspect screen. If clean, inspect screen after 10 hours of flight time. NOTE – In cases one and two, we are determining whether the small amount of metal was a “one shot and done deal” (not entirely uncommon).
  3. Chunks of metal ranging in size of broken lead pencil point or greater. Remove suction (sump) screen as large pieces of metal may have fallen into the sump. In any event, ground aircraft and conduct investigation. A mixture of magnetic and nonmagnetic material in this case often times means valve or ring and piston failure. Removing bottom spark plugs usually reveals the offending cylinder.
  4. Nonmagnetic plating averaging approximately 1/16” in diameter; may have copperish tint. Quantity found – ¼ teaspoonful or more; ground aircraft and investigate. If origin can’t be determined and this is a factory engine (not a field overhaul) that is under warranty, mail metal to Lycoming factory for analysis, to the attention of Product Support.
  5. Same as Item 4, but may be slightly larger in size and minus copperish tint. On direct-drive engines, propeller action may be impaired. Ground aircraft. If origin can’t be determined and it is a factory engine under warranty, mail material to Lycoming, to the attention of Product Support.
  6. Nonmagnetic metal brass or copperish colored. Resembles coarse sand in consistency. Quantity of ¼ teaspoonful or more – ground aircraft. If origin can’t be determined and it is a factory engine under warranty, mail metal to Lycoming, to the attention of Product Support.
  7. Anytime metal is found in the amount of ½ teaspoonful or more, it is usually grounds for engine removal. An exception should be where problem is confined to one cylinder assembly (rings, valves, piston, cylinder). In this case, if the entire engine does not appear to be contaminated, the offending cylinder assembly kit may be replaced. After corrective action is completed, conduct the routine ground running and screen inspection as previously described in Item 2.
  8. If any single or several pieces of metal larger than previously mentioned are found, magnetic or nonmagnetic, ground aircraft. If this is a factory engine under warranty, and origin of the metal contamination cannot be determined, a call may be made to the Lycoming Product Support Department. A good description of the metal may result in placing its origin. When phoning Lycoming or when returning metal removed from engines, supply the complete engine model designation, serial number, history of engine, oil temperatures, oil pressures and any odd behavior of the engine on the ground or during flight. NOTE – Metal samples for analysis can only by accepted if the engine from which the sample is taken is a new, rebuilt or overhauled engine from the Lycoming factory and it is still under warranty. Engines overhauled by other facilities may have parts that cannot be identified by analysis at Lycoming.

As an important postscript to “Suggestions if Metal is Found in the Screens or Filter,” factory personnel have become concerned over unnecessary engine removals because metal was found in a replacement engine after a prior malfunctioning engine was removed. These unfortunate engine removals were largely caused by maintenance personnel failing to thoroughly flush and clean all aircraft oil system components. Because of the difficulty of removing contamination from an oil cooler, it is strongly suggested that a new oil cooler be used with the replacement engine when an engine is removed because it failed. As a reminder that it is essential to remove metal contamination from the oil system, the factory Product Support Department now sends the following tag with every service engine leaving our factory:

Before installing this replacement engine, all aircraft oil system components, oil coolers, lines and supply tanks, where used, must be thoroughly cleaned for contamination. Lycoming will not be held responsible for contamination to this newly installed engine. 

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