Many of the aircraft engines produced today are equipped with full flow, spin-on oil filters. For long engine life, it is necessary to change both the oil and the filter at regular intervals. The information we receive indicates that problems are sometimes encountered because proper procedures are not followed when changing the spin-on filter. Therefore, it is appropriate to provide a few tips from a current service instruction.
The hardware that adapts many Lycoming engines for use of the spin-on oil filter includes an oil filter adapter (Lycoming Part Number 15047), and a converter kit (Lycoming Part Number LW-13904). Not all engines use the oil filter adapter because the accessory housing on some models is machined to take a converter kit and a spin-on filter. The kit includes a converter plate that has a gasket permanently glued to the plate; this gasket seals the plate on the side that faces the engine. If the spin-on filter seats too tightly against the opposite side of the plate when it is installed, the converter plate gasket may be slightly damaged when the oil filter is subsequently removed. This damage could result in oil leakage.
To prevent damage to the converter plate gasket, the oil filter gasket should be lubricated with a thin coating of Dow Corning Compound (DC-4) before the filter is installed. The filter should then be installed and hand tightened until the seating surface makes contact with the lubricated gasket. The filter should then be turned with a torque wrench until a torque of 18-20 foot pounds is reached. The 20 foot pound maximum torque should not be exceeded.
The oil filter element should normally be replaced each 50 hours of engine operation. Before discarding the element of the full flow filter assembly, an examination of the filter element should be accomplished. This examination is very important to flight safety, but recent reports indicate that some mechanics are not doing this check for metal that would warn of a developing engine problem and possible catastrophic failure. The full flow, spin-on filter may be opened by use of Champion tool CT-470. This tool is absolutely essential if the job is to be done correctly. The element is then removed from the filter and filter material is cut from the end caps. Carefully unfold the element and examine the material trapped in the filter. In new or newly overhauled engines some small particles of metallic shavings might be found, but these are generally of no consequence and should not be confused with particles produced by impacting, abrasion or pressure. Evidence of metal contamination found in the filter element requires further examination to determine the cause. (See Suggestions if Metal is Found...).
After the filter element has been replaced and properly torqued, the lock wire must be replaced and the engine run to check for oil leaks.
Textron Lycoming Service Publication SSP-885-1 provides information about the installation of engine mounted oil filters.