Oil leak

[a64pilot]

I have a rather large oil leak from the area of the base of the #3 cylinder, on the bottom, top is dry.
Any ideas, I have a hard time thinking its the cylinder base gasket, it’s been leaking forever just getting bad now so I have to fix it.
Wondering if a push rod tube can leak up from in flight air flow? The cylinder head area seems dry. Cylinders have about 175 hours on them, in 14 years.
Don’t say case crack please.

[2066]

A "little" oil leak can surely produce a lot of oil with the air moving through the cowling. I've had oil from push rod seals go "up" just as you describe...plus on the exhaust & "everywhere else". Occasionally you can turn a seal a bit & be lucky enough to slow (stop??) a leak -- check to be sure they're seated well on the lifter cover flanges, too, of course. Also, and I'm sure you know this, the tubes can loosen @ the head end causing oil to seep out & "around"(up). I've seen some suggest replacing leaking push rod seals with a "split" seal, but I've never heard that it really worked out -- there is a tool to tighten the head end without removing the cylinder. The Real Gasket folks came up with a nice tube "replacement" that's spring loaded and similar to Lycoming & new TCMs...can be worth while if leaks are bad & engine still long time before OH. (I didn't use the word "crack" at all.......oops! ). Mac

[6643]

The two aft nuts on the cylinder base flange are either through studs or through bolts for the center main bearing. Loosen them enough to determine of the studs are loose. If they are, and the two forward nuts on #2 are not, well, I won't say the word, but...

[phil123]

Your going to have to clean the engine to pretty much an oil free state. Use some cleaner degreaser from walmart or equivelant, careful of the paint that was shot on the case, if its the cheap rattle can type it will also be cleaned off ( ask me how I know) If the oil leak is bad enough it will show up in short order with a good runup. From there you can make a good determination of the leaks origin, once this is determined the easy part is replacing the bad component.....in most cases a dried out seal or possible pushrod tube swedge (not easy).

[a64pilot]

I’ve never taken a little Conti apart, I believe however to remove a push rod tube, the jug comes 0ff?
I have been Gunking and pressure washing to find the leak and oddly it doesn’t seem to want to leak on a ground run, but I’m nearly certain it’s bottom of #3 area, it’s not at the head and running down.
Sounds like I need to pull the Jug, that will tell me if a stud is broken, and I can replace all the possible leak gaskets.

I used to have that tool to swage the tube, I’ve moved a couple of times so it’s gone wherever things go when you move. I hope the tube doesn’t need to be swaged if it’s not currently leaking?

There is a small casting at the bottom of the tubes that attaches to the block, maybe so you can remove the lifters? anyway it seems the leak is closest to that?

I guess next step is to remove the baffling on that side and try to isolate the leak on run up I guess.

[a64pilot]

This is the push rod replacement kit? https://www.aircraftspruce.com/catalog/ ... PUQAvD_BwE
Looks to be worth investing in, if my leak is from this area and not a broken stud. I’m at 1000 SMOH so I’ll likely never overhaul it unless something pushes me into it.

[a64pilot]

I removed baffling so I could see in there and cleaned things off with carb cleaner. with just a minute or two idle it seems that the oil is coming from the cylinder stud that would be at 7 o’clock or so when viewed from the end of the cylinder.
I can’t get anything in there with the intake tube and pushrod tubes in the way to check torque.
So, if you have to remove the cylinder on these little motors to remove the push rod tubes, how do you get the base nuts off with he tubes in the way?

It looks to me that the jug is coming off, and I hope the stud isn’t broken

[2066]

CYLINDER TCM BASE WRENCHES ACS.jpg (50.42 KiB) Viewed 3083 times

Do you have these handy/available?

[phil123]

Check torque to the specs given (very important) normally those nuts will never loosen, if it checks ok I would try cleaning the stud/nut very good and try sealing the "outside" of the nut with proseal using a long screwdriver then let it cure for a couple days, I would try this first before pulling any jugs. Another possibility is the silk thread at stud has chafed away at the case half and allowed oil to seep through.

[a64pilot]

CYLINDER TCM BASE WRENCHES ACS.jpg
Do you have these handy/available?

Nope, never seen them.
I’ve done a few piston motors, Lycomings actually, I’m mostly a turbine guy to be truthful.

Just ordered the 1/2 and 9/16 from Spruce, surprisingly they seemed to be cheapest.