O-235 Oil Leak ID Line-Up!!

[Philly5G]

Do any of you O-235 drivers recognise this oil leak pattern and hopefully know the source of it please?!! As you can see, it’s either right above or just behind and between the generator and starter motor.

A double whammy is that there’s no oil filler extension on the dipstick mount and pouring oil in is a PITA and takes ages!! What have other people done to either devise a quick fill method, or extend the filler?

THANK YOU!!!

Philly


Sent from my iPhone using SuperCub.Org mobile app

[mike mcs repair]

More pictures. Look on top by push rods. Any bent push rods?


Sent from my iPhone using SuperCub.Org

[PerryB]

Pushrod tubes would be my first suspect.

[Philly5G]

BRILLIANT!! Thanks!! Sounds like the Push Rods are the most likely suspects so far


Sent from my iPhone using SuperCub.Org

[supercrow]

That sounds likely, but if not clean it up good and look for leaking between the case halves at the bottom of the engine. Not as usual in an 0235 as some others, but look for it. A case crack near the starter is not unheard of either. Total time on the engine?

[mike mcs repair]

also make sure the cylinder base nuts are tight......

[Philly5G]

That sounds likely, but if not clean it up good and look for leaking between the case halves at the bottom of the engine. Not as usual in an 0235 as some others, but look for it. A case crack near the starter is not unheard of either. Total time on the engine?

Total engine time around 1700 hours. Not jumping to the worse scenario yet, but case crack does sound very scary

[Philly5G]

also make sure the cylinder base nuts are tight......

Thanks for your help Mike, both the pushrod tubes and cylinder base nuts sound relatively straightforward to check, maybe

[tempdoug]

if you watch you can find these in lengths up to about 12 inches.https://www.ebay.com/itm/One-1-NEW-7...uTr:rk:3:-Pf:0

[aktango58]

Did you check the oil return hose and clamps? Those buggers love to leak all over the place!

Please take more pictures, but clean it up really well, then fly it for 20 minutes so we can get a better view.

[Philly5G]

Did you check the oil return hose and clamps? Those buggers love to leak all over the place!

Please take more pictures, but clean it up really well, then fly it for 20 minutes so we can get a better view.

Not yet, but you can be sure I will


Sent from my iPhone using SuperCub.Org mobile app

[skywagon8a]

Crankshaft seal? Check in behind the pulley groove on the flywheel for oil. If dry that's not it.

[Philly5G]

Crankshaft seal? Check in behind the pulley groove on the flywheel for oil. If dry that's not it.

Thanks skywagon8a!!! Will do

[stewartb]

Gravity is showing you where collected oil drips. With a pressure cowl that oil can come from someplace else. Get a sprayer and some Stoddard solvent and give the engine a bath, then watch for seeps and drips.

[Philly5G]

Gravity is showing you where collected oil drips. With a pressure cowl that oil can come from someplace else. Get a sprayer and some Stoddard solvent and give the engine a bath, then watch for seeps and drips.

Really good point, thank you! The aircraft has been stood for a lot of the time over the last few months, while I’ve been fixing various things, interspersed with test flights and I haven’t noticed any oil drips on the ground and it does seem that the oil only comes out in flight.

I also gave the cowls a really good clean when I originally took them off and oil then only appeared after the first flight after this. Any more clues in this?


Sent from my iPhone using SuperCub.Org mobile app

[stewartb]

There’s a sign on one of the machines in my shop that says “A Clean Machine is a Trouble Free Machine”. There’s a lot of truth to that.

[skywagon8a]

Philly, For what it's worth. It's been a long time since I've been actively involved with the O-235 engines. However it is my recollection that they would soldier on forever. That the only reason that they were torn down for overhaul after well more than 2000 hours was that the oil leaks became too numerous. Usually even then there was nothing mechanically wrong with them.

[TcraftF21]

Prop seal.

Jim

[Philly5G]

There’s a sign on one of the machines in my shop that says “A Clean Machine is a Trouble Free Machine”. There’s a lot of truth to that.

Thanks Stewart I COMPLETELY agree with that and a large part of the joy of doing the work on the PA-12 is cleaning it up, including the crud behind all the panels and the ton of work I did on the tail brace wires to make them look like new

Just cleaning the inside of the cowls took ages, to remove the (years? of) dried on oil and crud and now the engine is very inconveniently depositing more onto my nice clean surfaces!!! On a related point, I replaced the valve cover gaskets some months ago with silicon ones as suggested on the forum, but although the port side is now completely free of spatter after flying, the starboard side still has it, although less than before, any ideas?

[Philly5G]

Philly, For what it's worth. It's been a long time since I've been actively involved with the O-235 engines. However it is my recollection that they would soldier on forever. That the only reason that they were torn down for overhaul after well more than 2000 hours was that the oil leaks became too numerous. Usually even then there was nothing mechanically wrong with them.

THANK YOU for that SW!!! A very positive message to start the day with!! In the flying and testing I'm doing, it seems that the engine/aircraft are performing pretty much how they should, so the 1700 engine hours don't seem to have reduced its performance much!!

[Philly5G]

Prop seal.

Jim

Thanks Jim, I'll check this out too

[skywagon8a]

Thanks Jim, I'll check this out too

That's the same one to which I referred in post #12. Fixed pitch props don't have seals.

[Philly5G]

That's the same one to which I referred in post #12. Fixed pitch props don't have seals.

I guessed the prop seal was the same as the crankshaft seal at the prop end and thanks for confirming this SW

[Philly5G]

BRILLIANT!! Thanks!! Sounds like the Push Rods are the most likely suspects so far


Sent from my iPhone using SuperCub.Org

OK, I'm back on the oil leak hunt after doing a load of work and then, in the 2 hour shake down flight (everything worked!!) the engine lost just under 2 quarts of oil, maybe 1.75 quarts. I looked at the pushrod tubes and the front starboard one is leaking and I've attached a picture. I'm about to order replacements, but could this leak account for such a large oil loss?

[skywagon8a]

That amount of oil loss would have the engine swimming in oil. What does the inside of the exhaust pipe look like? Wet? That is only a few drops of oil on the front pushrod tube.

[TcraftF21]

Clean up the engine with solvent and then spray on some talcum power in spray can around the push rod tubes, engine case split line and around the cylinder bases. Go fly for a few minutes, land and look and any leak will show right up.

Jim

[Philly5G]

When I got back from the trip there was black oil running back from the starboard of the cowl over the boot cowl and a bit more added to the oil lying under the engine in the lower cowl, but certainly not swimming in oil What I have noticed though, is new/clean looking “jellified” oil collecting in the drip tray and continuing to drip out, I THINK from the clear tube that pokes out the back of the cowl (oil overflow?) pic attached


Sent from my iPhone using SuperCub.Org mobile app

[skywagon8a]

Philly, I do not see the equivalent of 1.75 quarts of oil leakage over a two hour period in your picture. Yes you are leaking some, though I suspect that you are burning most of it. What is inside your exhaust tailpipe? Wet, dark, oily?

[Philly5G]

Thanks!! That pic wasn’t after the 2 hour trip, but the picture would look pretty much the same, with just black trickles of oil on the starboard panels at the bottom.

Does burning the oil mean it’s going past the piston rings? The plugs DO get pretty oily and I need to clear them by leaning out the mixture immediately after start up and then running for 30-45 seconds at high power before the mag drops are in tolerance at 100rpm drop

I’ll check the exhaust when at the airfield later this week, but any thought on the clean looking “jellified” oil that’s still leaking out?


Sent from my iPhone using SuperCub.Org

[skywagon8a]

Just a guess from across the pond. It appears that the oil control rings may be tired allowing oil into the combustion chambers while the engine is running which would produce black wet spark plugs and a oily dirty exhaust pipe. The plugs getting oily and fouled at start up indicates residual oil in the combustion chamber from the oil control rings and/or worn valve guides. Where is the jellified oil coming from? The breather pipe? This would also be an indication of piston ring wear pressurizing the crankcase. What is the total time on the engine since overhaul? This is a symptom of a high time engine. When you pull the prop through by hand does it turn through compression easily or does it have a lot of resistance? Easily = worn rings and/or leaky valves.

[Philly5G]

That all sounds pretty likely. The engine is 1800 hours SMOH. I THINK the jellified oil is coming from the breather pipe, assuming this is the translucent tube at the back of the lower cowling? I’ll check the compression later in the week.

Assuming it IS all the above, is it overhaul time? or smaller fixes?

Thank you!!


Sent from my iPhone using SuperCub.Org

[skywagon8a]

It's been many years since I have been involved with 0-235s. However back then they just kept running until we got tired of wiping the oil off them. As I recall that was somewhere around 2100 -2200 hours. Official TBO is below those numbers.

This is Lycoming's TBO service instruction. https://flymall.org/aircraft/docs/Ly...ul%20Times.pdf It appears that they have increased the recommended times since I was active with the 0-235. These times are not considered regulatory in the States for privately flown airplanes such as your use.

You could remove the rocker covers and check how much wobble the valves have in the guides. This will give you some clues as to how much wear and whether the engine should be torn down or not. Look inside the cylinders with a light for scoring on the cylinder walls. This will address broken rings.

[Philly5G]

It's been many years since I have been involved with 0-235s. However back then they just kept running until we got tired of wiping the oil off them. As I recall that was somewhere around 2100 -2200 hours. Official TBO is below those numbers.

This is Lycoming's TBO service instruction. https://flymall.org/aircraft/docs/Ly...ul%20Times.pdf It appears that they have increased the recommended times since I was active with the 0-235. These times are not considered regulatory in the States for privately flown airplanes such as your use.

You could remove the rocker covers and check how much wobble the valves have in the guides. This will give you some clues as to how much wear and whether the engine should be torn down or not. Look inside the cylinders with a light for scoring on the cylinder walls. This will address broken rings.

Given the VERY high cost of O235-C cylinders, is having the cylinders repaired/reworked back to spec with new rings etc an option and have others done this?

[46 Cub]

OK, I'm back on the oil leak hunt after doing a load of work and then, in the 2 hour shake down flight (everything worked!!) the engine lost just under 2 quarts of oil, maybe 1.75 quarts. I looked at the pushrod tubes and the front starboard one is leaking and I've attached a picture. I'm about to order replacements, but could this leak account for such a large oil loss?

My advice would be to lovingly wipe off all the oil after each flight, and enjoy that plane until you are ready for an overhaul. I believe you have to pull the cylinders to change those pushrod gaskets and you don't want to do that unless you are ready for a major overhaul. O235 cylinders often have a benign 1/2" crack at the spark plug which is fine until you pull the cylinder and see it. They are also happy to fret at the case halves which is fine until you re-torque all your cylinders and bind your bearings. It appears to be a high time engine which is burning oil. There is nothing wrong with that, but it is likely unrealistic to pursue "perfect" with it. Actually unrealistic with any airplane but I certainly understand the desire....
The part about wiping the oil off.. (besides keeping the fire hazard low).. is it lets you have an opportunity to see something really wrong.. like broken exhaust, cracked cylinders, loose parts, etc.

[Philly5G]

My advice would be to lovingly wipe off all the oil after each flight, and enjoy that plane until you are ready for an overhaul. I believe you have to pull the cylinders to change those pushrod gaskets and you don't want to do that unless you are ready for a major overhaul. O235 cylinders often have a benign 1/2" crack at the spark plug which is fine until you pull the cylinder and see it. They are also happy to fret at the case halves which is fine until you re-torque all your cylinders and bind your bearings. It appears to be a high time engine which is burning oil. There is nothing wrong with that, but it is likely unrealistic to pursue "perfect" with it. Actually unrealistic with any airplane but I certainly understand the desire....
The part about wiping the oil off.. (besides keeping the fire hazard low).. is it lets you have an opportunity to see something really wrong.. like broken exhaust, cracked cylinders, loose parts, etc.

Thanks for this and very empathetic!! - Yes, I'm chasing perfection and would rather not be pouring oil in, just to wipe it off!! But the cost and hassle of an overhaul, or a new engine is very scary and if indeed the engine will run with black oil and not suffer any major problems with it, I can live with the pouring in and wiping off and in fact I've literally just fitted a longer oil filler so it's MUCH easier to pour oil in!! Just need to work some magic to reduce the wiping off

[Steve Pierce]

I ran an O-235C1 to 2600 hours. It burned a quart of oil every 3 hours the whole time I had it. Did lots of cross countries 5 plus hours to 10 hours each way and was pretty consistant. Pulled it and tore it down after it started using a quart every 2 hours on a trip back from Sun & Fun oone year. Compressions were always in the 70/80s. When I tore it down the camfer was worn out of the rings allowing the oil into the combustion chamber and burned. I leaned it all the time except the climb so never had oil plugs.

[Philly5G]

I ran an O-235C1 to 2600 hours. It burned a quart of oil every 3 hours the whole time I had it. Did lots of cross countries 5 plus hours to 10 hours each way and was pretty consistant. Pulled it and tore it down after it started using a quart every 2 hours on a trip back from Sun & Fun oone year. Compressions were always in the 70/80s. When I tore it down the camfer was worn out of the rings allowing the oil into the combustion chamber and burned. I leaned it all the time except the climb so never had oil plugs.

Thanks Steve, I lean right after start-up, go full rich for the mag drop checks and then lean until line up. Lean immediately after initial climb (sometimes during the climb if going high) and only go rich on entering the landing pattern

My compressions are 70+ on 3 cylinders and late 60s on 1.

The oil is black black black and goes black soon after an oil change, so definitely blow back. I'm now on the hunt for either cylinder refurb or recently overhauled used cylinders. As it's a C it's only 100hp (when new) unlike the heady 108/118 of the C1 and later versions. I'd consider an engine change, but would be a shame to split the engine/airframe partnership that's been together since 1947

[cruiser]

The killer for for the 0235 is the cost of cylinders. Their is a STC out there to put L cylinders on a C1 case in Grumman airplanes. Cylinder corner studs must be changed to 7/16”. Seems a no brainer to me at overhaul time with a deviation to a Piper airplane.

[skywagon8a]

There is nothing that says that the cylinders must be replaced unless they are damaged beyond repair. With normal wear and no cracks, perhaps replace the valve guides, grind the seats and a good hone job will put them back in service.

[DENNY]

Oil turning black quickly after an oil change can be caused by excessive valve guide wear. Cover up the holes in the top baffling will help keep things cooler.
DENNY