The International Cessna^® 170 Association

This likely seems like a simple question and I could probably google search it but just thought I would ask here. I did try to search on it first here in the forum but with with 133 pages returning from the search I gave up after looking through 8 of them.

My 152 had an oil filter so I just changed the oil like I would my truck. Since my 170 does not have an oil filter is there some sort of filter I need to clean or look at? I have heard of an ail screen but don't know where that is. Not hard to pull the quick drain plug but just making sure I do anything else I am supposed to do.

Also how may hours on the engine before changing and if I don't put those on very quickly how long in months before I should change the oil? Hopefully I always hit the engine hour interval but things get in the way sometimes.

Thanks,
Justin

Justin, there are two screens which are attached to the inside of the two big nuts you see safetied together most likely on the back of your accessory case.

The first caution. The oil temperature probe goes into the back of the fine screen. You need to use two wrenches, one to hold the nut closest to the engine and one to turn the other out and carefully pull out the probe. The probe is not exactly delicate but treat it and the stem with care. If you crack or break the probe or the stem you will be buying a new oil temp gauge or having yours overhauled. The second caution is the square nut on the screen is made of somewhat soft brass alloy and you need to be careful not to round it off if using anything other than a socket. Most people don't have a 1" square socket and use a wrench or worse an adjustable wrench. Your square nut is likely already messed up a bit. Don't make it worse.

Next to reinstall the screens and maybe a few other things, like if you loosen the nut for the temp probe that goes next to the screen, you will need new AN900 cooper crush washers. You will need a -28 for the fine screen, a -10 or -16 depending on the accessory case you have for the course screen and -10 for plugs and other places. BTW there are 3 different accessory cases. The oldest is called a 3 hole design because 3 bolts hold it to the sump. The later two are 5 hole designs. the AN900-16 is needed for the latest 5 hole design.

To clean the screens get a clear plastic jar like those used for peanut butter. Put some solvent in it and the two screens and swish it around till they are clean. You might also use a brass brush on the fine screen if it is clogged with stuff from years of use. Then pour the solvent through a clean towel and examine the particles like you would a cut filter.

Reinstalling the filter screens with the new crush gaskets you need to tighten them enough without over tightening. I was looking for a torque spec or some other official tightening limit but don't have all my resources with me. George has stated to turn these until the surfaces are just touching and then another 1/8 turn. I've also seen a reference on the web to turn them another 135 degrees. I think between 1/8 and 1/4 would work for me.

Here is another thread on the subject; http://www.cessna170.org/forums/viewtop ... f=24&t=638

How often to change your oil and clean your screens? 25 hours is a popular excepted time period. You want to check the fine screen each time, I check both.

Bruce,

Thank you for the detailed information. Much appreciated. I was thinking it was 25 hours without filter and 50 with but wanted to be sure.

Justin

If you should so desire, there is an adaptable accessory made for this engine that providea for the installation of an oil filter.

Thank you blueldr, Maybe I can get that put on down the road somewhere.

Justin

A Bruce mentioned, be very careful reinstalling the temp probe.... If you overtighten it, you may crack or break it....but that it's not the dangerous part.... The bad part its,....when it breaks, it dumps all the oil overboard while in flight!!!!
Only tighten the PROBE 1/8 " after it bottoms.... Tighten the screen, with a new AN900, 1/4 turn.
Remember, theres little or no oil pressure on the screen or probe...only gravity.

gahorn wrote: Only tighten the PROBE 1/8 " after it bottoms.... Tighten the screen, with a new AN900, 1/4 turn.

Ah haaaa caught you doubling the specs you quoted in 2003 George.

gahorn 2003 wrote:Install a new copper crush washer (AN900 gasket) on the screen and re-install it until it bottoms out. Then tighten it an additional 1/8 turn. Re-install the oil temp bulb and tighten the nut until it bottoms and then only slightly snug it beyond that (less than 1/16 turn.)

The point is be careful. tighten less than you think. Then do a leak check run (you will run the engine and check for leaks right) then tighten a wee bit more if necessary and check again till no leaks then safety.

Can I pick up these AN900 gaskets from any general auto parts store or are they aircraft specific?

Justin

AN900's are CHEAP from Aircraft Spruce:
http://www.aircraftspruce.com/catalog/e ... ckkey=3822

Bruce Fenstermacher wrote:
Ah haaaa caught you doubling the specs you quoted in 2003 George. .....y.

A-ha!....You didn't read the latest REVISION, did you!

gahorn wrote:Only tighten the PROBE 1/8 " after it bottoms.... Tighten the screen, with a new AN900, 1/4 turn.
Remember, theres little or no oil pressure on the screen or probe...only gravity.

I think I just found the cause of my perpetual leak on my filter adapter.
I've swapped that gasket three times, cranked it down every time and it still leaks.
I think I'm cranking a bit too much.

bagarre wrote:

gahorn wrote:Only tighten the PROBE 1/8 " after it bottoms.... Tighten the screen, with a new AN900, 1/4 turn.
Remember, theres little or no oil pressure on the screen or probe...only gravity.

I think I just found the cause of my perpetual leak on my filter adapter.
I've swapped that gasket three times, cranked it down every time and it still leaks.
I think I'm cranking a bit too much.

That depends upon WHICH adapter you have. Follow the specific instructions of the manufacturer.
The F&M adaptor requires specific (high) torque, in association with their specific gasket.

Bruce Fenstermacher wrote:You will need a -28 for the fine screen, a -10 or -16 depending on the accessory case you have for the course screen and -10 for plugs and other places. BTW there are 3 different accessory cases. The oldest is called a 3 hole design because 3 bolts hold it to the sump. The later two are 5 hole designs. the AN900-16 is needed for the latest 5 hole design.

I really hate to ask but I don't know the answer so further guidance is needed if possible. All of you didn't just wake up with the knowledge you have...right? So please be patience with the unlearned among you.

I looked at my plane and I see the two nuts safety wired together and the oil temp prob. What I don't understand is how to determine if I have the 3 hole or 5 hole accessory case. Not sure what to look at to determine that. If there's not an easy way to tell I will just by enough of both AN900 washers and see which one fits.

Thanks,
Justin

Three hole sump.

Thank you very much guys. I'm a little less unlearned now.

Justin