Engine screens

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Engine screens

Postby MoonlightVFR » Wed Mar 30, 2016 1:24 pm

I read on forums about engine screens

Could some one clarify difference between coarse screen and fine screen. Where located? Part Numbers?

Why are there two screens?

Should a screen ever be replaced?
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Re: Engine screens

Postby HA » Wed Mar 30, 2016 5:26 pm

the oil screens are located on the bottom rear of the engine accessory housing. LH smaller one is a coarse screen, that is the inlet screen. RH larger one is a finer screen, that is your main "oil filter" screen. No need to replace them unless something clogged one causing it to collapse, then you had bigger problems anyway.
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Re: Engine screens

Postby Bruce Fenstermacher » Wed Mar 30, 2016 5:35 pm

Screens are in the bottom of your accessory case, or where before there might be a oil filter adapter installed. The course screen pn#633272 item 45 on the left in the illustration is behind the outer hex "nut" you will find there with a plug in the hex. If no adapter is installed you will find the fine screen pn#53003, item 41 behind the 1" square "nut" which should have the oil temperature bulb installed in it. The course screen is just as described, course. It will let larger metal parts through. The fine screen is as described, finer than the course screen and will catch much much finer material. I'd guess the reason for two screens is just a way to provide more screen area for material rather than just one fine screen. Why not two fine screens? I'm guessing it would be to much restriction.

Screen Shot 2016-03-30 at 1.28.31 PM.png

A screen should be replace on condition. If it is damaged in a way that would allow unscreened oil passage such as a hole or restrict oil passage such as if the screen got corroded shut.

Normally you just pull the screens and visually inspect what contaminates you might see on the surface of the screen. Then put them in a clean transparent container, such as a empty plastic peanut butter jar, with some solvent. Swish the solvent around the screen to clean it. Then pour the solvent and contaminates that you will no doubt find in it from the screens, through a cloth like a t-shirt or other suitable material leaving just the material. You can then examine the material to determine what it might be. Most of it is probably black carbon. You will likely also find particles of brass from bearings and perhaps a flake or two of aluminum from things such as piston pins. Anything that sticks to a magnet is ferrous metal from a cam, cam follower, gear or perhaps cylinder wall. Though unnerving to find, metal material in small quantities of say 1/4 teaspoon are normal. Of course less is better. You will almost always find something. After cleaning the screens with solvent and inspecting them for condition, they are reinstalled with a new crush gasket. Many people do not pull the course screen at ever filter change because the parts it would catch are said to be big enough for part numbers and it's likely you would have some other indication of an issue.
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Re: Engine screens

Postby c170taildragger » Sun Feb 16, 2020 3:01 pm

If an oil filter adapter with the external filter has been installed are the fine and course screens removed?
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Re: Engine screens

Postby gfeher » Sun Feb 16, 2020 9:54 pm

My '52 170B has the Cessna oil filter adapter and just the fine screen is removed. Part of the annual or 100 hr inspection is removing, inspecting and cleaning the coarse filter.
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Re: Engine screens

Postby gahorn » Mon Feb 17, 2020 1:45 am

gfeher wrote:My '52 170B has the Cessna oil filter adapter and just the fine screen is removed. Part of the annual or 100 hr inspection is removing, inspecting and cleaning the coarse filter.

This is also how most aftermarket spin-on filter adaptors are installed. I have the FM Enterprises (aka El Reno, Tempest) system which replaces the fine pressure-filter but retains the coarse suction-filter.
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