8KCAB Changing oil in 8KCAB

Halhayden

Halhayden

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Prescott, AZ
Who does their own oil change in their decathlon? I’m tackling mine in my 1976 Decathlon for the first time. My shop says they always have to pull an oil screen and check it in addition to changing the filter. But he implied that when I do an “owner oil change”, I might have an option to pull the screen or skip it.

Any thoughts / opinions / experience on this?
 
I've done my own oil changes, O-320 with a filter. I don't know about a screen? The hardest thing was getting the cowling back on... By myself of course..
 
As an A&P I only pull the screen at the annual. The screen catches larger partials mostly I find carbon chunks. The filter catches the smaller things like aluminum. When doing an oil change you should be cutting the filter then in a clean pan rinse it in gas and filter the gas and look for what’s left. Now depending on use may change how you want to look at it.
 
If all you want is clean oil it doesn't hurt to skip the screen. The screen is easy enough to check, but mine is always particle-free, so I do it about every third oil change.

If it is a Christen system, there is a plug that is held in place with the screen. You cannot see it, so use some care not to dis-lodge it. Every seven or eight years my O Ring on that plug will go bad - special Lycoming part number - symptoms include hesitating return of oil pressure when inverted, and also several second recovery when rolling right-side up.
 
Very helpful info… thanks guys! Got it finished today so am ready to fly again. I have to say, removing and reinstalling the cowls is the challenging part of the job. In the Bonanza, I just pull the cowl release levers and pop them open.
 
I do it all the time on mine. For future reference by others:

There are 2 screens: a pressure screen in a housing at the top rear of the engine, and a suction screen in the oil sump at the bottom rear. If you have an oil filter, then the pressure screen has been replaced by that.

Technically an oil change by the book requires checking and cleaning both screens.

However, the suction screen is a bit of a PITA, because it is in an awkward location and requires safety wiring. The suction screen mesh holes are larger, so metal particles will usually show up in the pressure screen or filter first. For that reason, many people do not check the suction screen at every change. Once a year is a common compromise.

I recommend going on Aircraft Spruce and ordering a half dozen gaskets for the pressure filter (if you have one), and a half dozen crush washers for the suction screen. Both are cheap, so you might as well have a new one on hand when the mood strikes. A pair of stubby wrenches for the hose fitting on the suction screen comes in handy, as does a 1/4" thumb ratchet and extension for the pressure screen.
 
I've seldom seen (or done myself) removal of the oil sump suction screen unless a problem crops up indicating poor oil flow. The screen is too course to really (filter) anything out. Of course if something was to be dropped into the sump during an oil change or maintenance then the screen/plug would come out...
Lots of airframe/engine mounts preclude removal of the oil sump screen during a routine oil change because of a tubing member in the way.
Personally I've never split a Lycoming case and found anything in the lower screen of any note.

JMPO
Chris
 
Technically an oil change by the book requires checking and cleaning both screens.

Always willing to learn - which book might that be?

I agree it is a good idea, but did not know it was required.

I lost that little plug once, and to get it out required dropping the sump. Yuk.
 
Bob Turner said:
Always willing to learn - which book might that be?
Click to expand...

Lycoming Service Bulletin 480F

Bellanca Service Manual for 8KCAB models 1972 thru 1979
 

Attachments

Got me - I have one of those in my shop. Guess I should read it more often.

Still, we should use common sense - a lot of folks repack their wheel bearings annually (but never repack the wheels on their car between brake jobs). Which would be more likely and dangerous - losing a wheel due to lack of lubrication on the runway or on the freeway?
 
Bringing up a thread from the past. The POH says to do a complete oil change one must unhook the lines for the Christian oil system and drain them. Apparently there is an extra 2 qts of oil in there. 8 in the engine and then another 2 within the inverted system for a total of 10. Does anyone actually do that?
 
I did it once. Since then, haven't really felt the motivation. But I roll upside down once a week. If you do not exercise the system, I would clean it out once in a while.
 
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