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O-235 Oil Leak ID Line-Up!!

The spring comes with the seal. Hooking the ends together is difficult for those with fat fingers. You might practice this away from the engine first. Sometimes it helps to preload a small twist in the spring to prevent it from unhooking.
 
Found a YouTube video showing this seal being fitted to an O540 - boinnnnggggggggggggg!!!!!

Is that special tool that curves around the prop flange essential?


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And here's the link to the how to video https://www.youtube.com/watch?v=sANfkgRBHpw boinnnnggggggggggg!!!

I also found this very useful thread https://mooneyspace.com/topic/8244-crankshaft-seal-split-or-not/ which contains nuggets of gold like "Remove the spring, tape the crank flange good with electric tape to cover the sharp edges, warm the seal up in hot water lube everything up and it will actually go on easier than you think" :)

Unfortunately it also says that "If the crankcase is building pressure, it will make the seal leak" and as regular readers and contributors of this thread know, it's likely that my crankcase IS building pressure from the oil control piston rings :(
 
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Unfortunately it also says that "If the crankcase is building pressure, it will make the seal leak" and as regular readers and contributors of this thread know, it's likely that my crankcase IS building pressure from the oil control piston rings :(
I would change that "will" to could make the seal leak. A seal is more likely to leak if there is a buildup of crankcase pressure which can be from worn piston rings.
Also it is easier to install the spring on the one piece seal than it is on the split seal since the split keeps moving and knocking the spring out of the groove.
 
Thanks for this. Is it possible to “easily” inspect the area where the old seal has been? and if not easy, what’s the best way to do the inspection?

A small mirror like a dentist's mirror can be useful. The new cheap flexible borescopes like the Vividia should be useful,too.

Do the replacement seals come with a spring? or is the existing one reused? Interestingly, I don’t see the spring listed in the parts list?

As Skywagon said the spring is part of the seal. The spring gets removed for installation for both the split seal and the one piece seal and then reinstalled. You may end up making tools out of safety wire or loops of dental floss or such to hook and maneuver the spring ends for reassembly. Somewhere I saw a suggestion for covering the prop hub with a plastic bag and lots of lube for one piece seal installation, the idea being to protect the lip from damage as much as possible. So far in my limited experience split seals have worked just fine when you follow the directions.
Also check the parts book carefully by model and serial number. Some engine/seal combinations use retainer plates after the seal is installed. The retainers and an unobstructed vent line would eliminate the possibility of a seal blowout.
 
Thanks for this. Is it possible to “easily” inspect the area where the old seal has been? and if not easy, what’s the best way to do the inspection?

A small mirror like a dentist's mirror can be useful. The new cheap flexible borescopes like the Vividia should be useful,too.

Do the replacement seals come with a spring? or is the existing one reused? Interestingly, I don’t see the spring listed in the parts list?

As Skywagon said the spring is part of the seal. The spring gets removed for installation for both the split seal and the one piece seal and then reinstalled. You may end up making tools out of safety wire or loops of dental floss or such to hook and maneuver the spring ends for reassembly. Somewhere I saw a suggestion for covering the prop hub with a plastic bag and lots of lube for one piece seal installation, the idea being to protect the lip from damage as much as possible. So far in my limited experience split seals have worked just fine when you follow the directions.
Also check the parts book carefully by model and serial number. Some engine/seal combinations use retainer plates after the seal is installed. The retainers and an unobstructed vent line would eliminate the possibility of a seal blowout.

As oil continues to drip out of the vent tube into the drip tray after flying and for a couple of days afterwards, I suspect the vent tube is pretty unobstructed :)
 
I've found that leaky crank seals don't tend to leak much oil out of themselves but they do tend to send oil out of the breather. Don't know about that on Cubs but have seen that on other planes. For philly 55 g are you sure none of that oil is coming from between the case halves? Case fretting happens. If you attempt a fix involving retorquing all the cylinders without complete disassembly and line-boring you may invite more trouble than hoped for. Living with some oil leaks until ready for overhaul (which is just disassemble, inspect, and repair as necessary to service limits) might just be better than the alternative.
 
I've found that leaky crank seals don't tend to leak much oil out of themselves but they do tend to send oil out of the breather. Don't know about that on Cubs but have seen that on other planes. For philly 55 g are you sure none of that oil is coming from between the case halves? Case fretting happens. If you attempt a fix involving retorquing all the cylinders without complete disassembly and line-boring you may invite more trouble than hoped for. Living with some oil leaks until ready for overhaul (which is just disassemble, inspect, and repair as necessary to service limits) might just be better than the alternative.

I’ve cleaned pretty much all the liquid(ish) oil off the engine in prep for the trip around the pattern oil leak test in the next few days.

I already know that SOME oil is leaking from the starboard front pushrod tubes, SOMEWHERE above the generator, the starboard valve covers AND quite a bit from the breather/overflow tube IN ADDITION to the oil being burned and leaving its witness marks on the starboard inner gear tube. So I think the oil test will confirm these, although who knows, there MAY be revelation!!

I’m certainly not intending to remove any cylinders etc, so unless there’s something obvious, crankshaft or pushrod seals or loose bolt somewhere, I’ll be filling up and wiping off until the end of the season and then calling in the proper engine boys to do the do :)


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I'm no expert, but I ordered an extension for my O-235 and the threads were different on the one I received. It is a PITA to fill with no neck!

100% agree on the no neck fill PITA!! It now takes maybe 20 seconds to pour in 1 litre/quart of warm oil with no mess or drips, compared to the (at least) 4/5 minutes+ before AND no oil covered flexi funnel/tube to store!!!

The used (Lycoming) oil filler extension/neck I ordered screwed straight and securely into the case and wirelocked in. The dipstick it came with has a chamfer on the lowest threads, so doesn’t engage until the last turn, but feels secure enough. The biggest job was modifying the dipstick to add an extra 1.5” to reach to the 1 and 2 litre measurements, but now it looks FAB!!!IMG_5109.JPGIMG_5111.JPG


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Success on phase 1 of the oil leak hunt!!!!!!

I combined the new tailwheel test drive around the airfield with a decent engine run, before the flying the pattern test next week and I'm sooooooo happy to say that a couple of oil leaks have already shown themselves!!!!! :)

Following the great advice in this thread, I cleaned the engine as well as I could on Saturday and it worked brilliantly!!!! as on shutdown today, the 2 leaks were immediately obvious!!!!!

The first one is coming from the rear starboard, lower (rear?) cylinder base bolt(s)

zTtY5GyXT1+oZPq+6Bg1Tw.jpg VX48x5dTSOWsHiQe6j7e3g.jpg

and the other one, somewhere above the generator bracket

c2dazzYtRXSJamWEYsMDTg.jpg

Further investigation is obviously needed to get to the source of the 2nd leak and I may remove the prop to remove the nose bowl. On the 1st leak, would tightening those bolts be an easy fix, or something to try? Or does it fall into the category of the warning from 46 Cub "If you attempt a fix involving retorquing all the cylinders without complete disassembly and line-boring you may invite more trouble than hoped for. Living with some oil leaks until ready for overhaul (which is just disassemble, inspect, and repair as necessary to service limits) might just be better than the alternative."

I'm REALLY excited to be getting somewhere on this leak hunt :)
 

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The first one is coming from the rear starboard, lower (rear?) cylinder base bolt(s)

View attachment 42241 View attachment 42242

and the other one, somewhere above the generator bracket
View attachment 42243

Further investigation is obviously needed to get to the source of the 2nd leak and I may remove the prop to remove the nose bowl. On the 1st leak, would tightening those bolts be an easy fix, or something to try?
Leak #2 is likely the crankshaft seal behind the prop. A relatively east fix as we have described.
Leak #1 is an "O" ring around the cylinder base which has dried out over the years. Leave it alone...put up with it. ​The fix is to remove the cylinder to replace it. With 1800 hours on the engine leave it alone and just wipe it off. Don't open that can of worms until you are prepared to overhaul the engine.
 
Leak #2 is likely the crankshaft seal behind the prop. A relatively east fix as we have described.
Leak #1 is an "O" ring around the cylinder base which has dried out over the years. Leave it alone...put up with it. ​The fix is to remove the cylinder to replace it. With 1800 hours on the engine leave it alone and just wipe it off. Don't open that can of worms until you are prepared to overhaul the engine.

Any mileage in putting "something sealantish" externally around this joint to help the O ring, without removing the cylinder and saying hi to the worms? ;)
 
Any mileage in putting "something sealantish" externally around this joint to help the O ring, without removing the cylinder and saying hi to the worms? ;)
I've not done such a thing. Though I see no issue with using a sealant which does not harm the crankcase and cylinder metal. Something which can easily be cleaned off when the time comes to do the overhaul. Perhaps someone else here has used such a sealant? There is no pressurized oil behind this leak other than crankcase pressure. It's only messy.

As I've told you earlier, the biggest issue that I've seen with the O-235 engine is oil leaks. When the time comes that the leaks exceed your patience for cleaning and putting up with them, then it is time to overhaul.
 
Wiping oil off my aircraft is one of my very least favourite things, so my patience is pretty limited in this area to start with :)


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Wiping oil off my aircraft is one of my very least favourite things, so my patience is pretty limited in this area to start with :)
There comes a time when the engine will talk to you and say "Phil it is time, open your wallet". You will know when this time has come.
 
Ha ha ha ha ha!!!!!!!!!!

It’s currently saying “Philly I’m in good shape, I start and run beautifully and I’ve been together with this body for 72 years. I know I’m a bit leaky and dribbly, but if you can help me out with some incontinence treatment or products, I’ll continue to do my best for you and PLEASE don’t replace me with a younger model, or send me in for major surgery, I’M FINE!!!!!!! REALLY!!! xxxx”


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Hmmmmmmmm either I'm getting very lucky or getting very confused now!! I borrowed a Lycoming Cylinder base nut spanner and torque wrench set to 300 inch/pounds and checked the torque of the 2 (3/8") base cylinder nuts where the oil was coming from. The back one was fine, but I got maybe an 1/8 of a turn on the front one and felt disappointed they both weren't looser and this was therefore an easy find. I couldn't do any more work on the oil filler flap fabrication, as waiting for the Dzus to arrive, so put the lower cowl back on and went for a flight in the Spring sunshine :)

I've done a lot of work on this aeroplane and everything worked beautifully :) :) and the whole flight felt like the end (at least the initial part of!!) of the journey. After getting back, on looking at the side behind the starboard cowling and the starboard undercarriage top fairing, after getting out, I noticed less oil spatter and runs than usual and on opening the side cowl, I was pretty amazed that there were was NO oil at all under those 2 cylinder base bolts and just a few large drops at the front of the base cowl, which I'm guessing are from the other oil leak, which we suspect is the crankcase oil seal!!! So either:

1. That 1/8 of a turn made the difference
2. Running at an oil level of 5.5litres (nearer 4 before) made a difference
3. Running at 2350 (rather than 2400) for the bulk of the flight made a difference
4. The leak is still there but the oil was blasted from there to the front of the lower cowl!!!

Any thoughts please?!!!
 
Check the torque on all of the nuts to be certain that they are equal. A loose one can cause a tight stud to break by increasing the loads on the tight one. sounds like you are getting lucky.
 
Check the torque on all of the nuts to be certain that they are equal. A loose one can cause a tight stud to break by increasing the loads on the tight one. sounds like you are getting lucky.

Good idea and I'll check the rest when I'm back out there tomorrow :) Do you think that even such a tiny 1/8 of a turn could make the difference to stop the leak?
 
Cylinder bases do start to leak over time. So I just assumed that yours were leaking due to the 1800+ hours on the engine. 1/8 of a turn loose is a lot. So yes it could have been the cause of the leak. It could have just been loose. It could have been loose since new. It could have a stud which is in the process of stretching and breaking.

I have found those internal wrenching cylinder nuts hanging by their safety wire with a piece of stud still in the nut. Several on one engine even. The same engine also had cracks in the crankshaft flange between most but not all of the lightening holes.
 
Cylinder bases do start to leak over time. So I just assumed that yours were leaking due to the 1800+ hours on the engine. 1/8 of a turn loose is a lot. So yes it could have been the cause of the leak. It could have just been loose. It could have been loose since new. It could have a stud which is in the process of stretching and breaking.

I have found those internal wrenching cylinder nuts hanging by their safety wire with a piece of stud still in the nut. Several on one engine even. The same engine also had cracks in the crankshaft flange between most but not all of the lightening holes.

I've got to say, the engine looks really good from the outside, paint good etc and seems to be in pretty good condition. The aircraft was used commercially for aerial photography (and then basically sat pretty much unused for 16 years) and the fast drain oil valve and the no oil filler neck (I'm guessing oil pumped and not poured in) point to it being a working tool, so the engine probably got a fair amount of attention. I'll let you know about the other nuts and how they are against the 300 inch/pound torque.

THANK YOU SkyWagon8a for your really brilliant and consistent help along this thread :)
 
You're welcome Phil. I'm not always right, but I try.
Remember that there are two sizes of studs/nuts on those cylinders. That means that there are two different torque values.
 
You're welcome Phil. I'm not always right, but I try.
Remember that there are two sizes of studs/nuts on those cylinders. That means that there are two different torque values.

Thanks again my friend!!

I thought there were 2 types of nuts, but looking at the parts manual https://www.lycoming.com/sites/default/files/O-235 Parts Catalog PC-302B_0.pdf page 3-5, on the C models they're all the same - 32 * Part 11 - 3/8 nut and the torque settings in the limits manual page 1-35 (my O235-C being Chart A) https://www.lycoming.com/sites/default/files/SSP-1776-4 Table of Limits - Complete.pdf has the torque for 3/8 Cylinder hold down nuts at 300 inch/pounds, unless I'm reading this wrong?
 
As I said, it has been a while since I worked on an 0-235. It does appear that all 8 cylinder hold down nuts are the same size. 3/8-24 and the torque is 300 in-lbs. You are correct.
 
As I said, it has been a while since I worked on an 0-235. It does appear that all 8 cylinder hold down nuts are the same size. 3/8-24 and the torque is 300 in-lbs. You are correct.

I checked all the cylinder hold down nuts I could access without taking the baffles off and they were all 300 inch/lbs, or maybe more!

I also checked the oil filter at the back/top of the accessory housing and no collection of metal filings in there at all!!

I'm going to fly it quite a bit now and keep a close eye on the oil consumption and if the front leak continues, remove the baffles so I can see more clearly where it's coming from :)
 
...I'm going to fly it quite a bit now and keep a close eye on the oil consumption and if the front leak continues, remove the baffles so I can see more clearly where it's coming from :)
Chances are good that it is the crankshaft seal behind the prop. Not a big deal to fix.
 
Chances are good that it is the crankshaft seal behind the prop. Not a big deal to fix.

Yes, I looked at this the best I could with the top cowl off and peering through the nose bowl holes, could see some old oil inside the propeller boss, but nothing new. I'll keep a close eye on it :)
 
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