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Crankshaft seal oil leak - how easy to address?

alpinelakespilot2000

Well Known Member
While my prop is in for a repitch, I've been trying to track down the source of some nagging oil drops. After a couple hours flying they show up on my starter hold down studs, my alternator hold down studs, on the lower port side baffles in front of #2 where they wrap around the cylinders, and on the baffles just behind the starter ring on the upper port side. Given that I'm only 100hrs into my new Aerosport 0-320-D2A, it's hard to tell whether it is having any effect on my oil consumption, but it does create just enough of those droplets to be a nuisance, though not so much that they end up on my cowl to any noticeable degree.

Anyway, while I had the prop off, I decided to pursue a suspicion I've had for some time. It appears that my leak might be coming from the crankshaft seal at the front of the case, primarily at the 5:30-6:00 position.

90brs3.jpg


If this is, indeed, the source of my leak, what are my options for addressing it? Is there anything that can easily be done, or is this one of those "open-heart surgery" type of issues that makes the currently minor leak worth living with?

Thanks for any thoughts.
 
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I had a similar issue with my O-360-A1F6D. It was off a C177 with a CSP. It was installed in my RV-4 with a FP prop. The rear crankshaft plug was not punctured so oil pressure was building up in the crankshaft behind the prop. Puncturing the plug solved the problem.

I cannot tell if your engine has a solid or hollow crankshaft, but if hollow this might be the problem. I'm sure that someone with much more knowledge will chime in, but wanted to give you my experience.
 
This is a super easy fix, with the biggest challenge being simply believing that what I am about to say is true.

Remove the old seal -- I put a couple of sheet metal screws into the front of the seal and then used a screwdriver under the heads to "pry" the seal out.

Get a couple of new seals (one-piece, not the split seals that are available). Remove the spring that is in the rear of the seal by unhooking the ends. Set this aside -- you will need the spring shortly. BTW, the seals are so cheap that having a second one on hand is just good insurance in case you goober things up.

Also head down to the local thrift store and purchase an electric frying pan about 1-1/2" deep. Put some engine oil in the pan and also toss in the seal. You want to warm this puppy up to a couple hundred degrees.

While it's warming, put some duct tape over the edges of the crankshaft flange, and then smear something slick over the duct tape. I used some lithium grease, but anything slick works.

Once the seal is hot (takes ~30 minutes for the heat to saturate the seal), fish it out with a screwdriver. Make certain that you are wearing gloves to protect yourself from getting burned, abut stretch the seal and pop it over the flange. It will be super elastic, and this is really easy to do.

Put the spring back into the seal. This is sort of a pain, but not too bad. Clean any grease off the seal and press into place.

Use some sealant around the edges of the seal (outside edge). I can't remember for sure, but might have used RTV. Let this set up for a couple of days before cranking the engine.

It's harder to describe than to do!
 
Don't do what a local Bonanza driver did, use a microwave to heat up the seal.

It will turn into a pretzel...:)
 
I cannot tell if your engine has a solid or hollow crankshaft, but if hollow this might be the problem.
Thanks for the thought, Chris. My D2A can easily be turned into a D1A for a constant speed prop, so I think I do have a hollow crank, right?

However, would something inside the crank (e.g. inner seal not punctured) cause it to leak on the outside? (Not doubting, I just have no idea what everything looks like inside!)
 
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mculver has it right

There are two different types of springs that go behind the seal. One that threads in and one that hooks in. When removing. I've always used picks. Make sure you let it heat up for a while first. Buy two because the first one might break. Two speeder handles make for a great tool to install the main seal. Once you have it on, then put on the spring, make sure it goes deep in the groove all the way around. Sometimes screwdrivers are needed to be placed in some of the flange holes while you work it around. Get a friend to help you if you have never done this before. Make sure you get the orientation correct as well. I've found several of the springs not installed all the way. Then the adhesive needs to be gooped on liberally. DON'T MICROWAVE ANYTHING. Use a bowl with hot oil.
 
This is a super easy fix, with the biggest challenge being simply believing that what I am about to say is true.

Remove the old seal -- I put a couple of sheet metal screws into the front of the seal and then used a screwdriver under the heads to "pry" the seal out.

Get a couple of new seals (one-piece, not the split seals that are available).
Yes, I see what you mean about believing this could be easy. I'm still skeptical but definitely feel encouraged by your optimism!:rolleyes:

However, how would I use a one-piece seal? How would I get it around a crankshaft on an already-built engine? The crankshaft flange (to which the starter ring is bolted) is probably 5-6" in diameter! I don't see a one-piece seal going around that. I must not be visualizing something right.

Despite my lingering confusion, thanks for everyone's help. I'm starting to think that if my leak is here that maybe it's not the end of the world, or of my $20K engine!
 
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Easy

Steve, get the one piece, have a friend with a speeder handle and you with a speeder handle put the seal up to the flange. Then one of you go on one side and the other work it around. I've done so many it's hard to count! They are easy once you get the hang of it. Or take it to a mechanic and watch him do it.
Best,
Brian
 
Steve, get the one piece, have a friend with a speeder handle and you with a speeder handle put the seal up to the flange. Then one of you go on one side and the other work it around. I've done so many it's hard to count! They are easy once you get the hang of it. Or take it to a mechanic and watch him do it.
Best,
Brian
Ok, thanks Brian. Do you mean "spreader" handle or "speeder" handle. I never heard of the latter. It does sound, though, like what your are telling me is that the seal will go all the way around the flange and then shrink back to the size of the crankshaft.

BTW, is the black ring looking thing in my picture the actual seal?
 
yes

It goes over and shrinks back.... I promise. Yes the seal is black. Speed handle... like a speeder with a bit holder and a socket.... about a foot long with a jog in the middle....
 
If this is, indeed, the source of my leak, what are my options for addressing it? Is there anything that can easily be done, or is this one of those "open-heart surgery" type of issues that makes the currently minor leak worth living with?

Thanks for any thoughts.

That doesn't look like much of a leak to me and there's no evidence it is the crankshaft seal. If there is oil on the inside of the flywheel then it is leaking otherwise it could be leaking at the case halves there which there's nothing you can really do about in the practical sense. I would leave it alone.
 
Not difficult

I replaced the seal on my Bonanza IO-550. I used two round shaft screwdrivers but first polished the shafts so they were nice and smooth. One held the seal in place and the other was used to pry it around the flange. Also, lube the heck out of the seal and the flange, and cover the flange with a plastic Baggie. It slipped on so easy it was surprising. I didn't heat it, but hey... This is Florida.

Use copious amounts of Tite-Seal behind it. I had it replaced before and the new one leaked, so I think Tite-Seal really helped.

Continental recommends polishing the shaft before installing the new one. Look at yours closely.

Don
 
Leak

You call that a leak ? I would call it normal seepage for an aircooled engine .

When I change them out I have a propane camp burner and use boiling water , a loop or two of masking tape around the flange and a seal tool . The Lycoming book recommends "Pliobond " as a sealant / adhesive .
Tom
 
That doesn't look like much of a leak to me and there's no evidence it is the crankshaft seal. If there is oil on the inside of the flywheel then it is leaking otherwise it could be leaking at the case halves there which there's nothing you can really do about in the practical sense. I would leave it alone.
Yes, there is a bit of oil and grime in the aft side of the flywheel, and I suspect there would be more if it didn't get thrown off by rotating as fast as it does.

You call that a leak ? I would call it normal seepage for an aircooled engine.
I've been kind of wondering how much seepage I should expect from a new engine. Maybe what I do have is normal, I just have no reference since this is the first plane I've owned.

Thanks to all.
 
SEAL

Note that the SI only allows for two adhesives. Titeseal is a non hardening sealant and is NOT APPROPRIATE for use on the crank seal.
 
Pliobond

Wonder if Chief Aircraft or Spruce will ship it ? I buy it local ( Deland Fl. Chief) .
Tom
 
Bad luck with Pliobond

I had a reoccuring leak on the front seal even after replacing it several times and installing with pliobond. It would not leak for 50 to 100 hrs but would always begin to leak again. I could always get the Pliobond locally at the Ace hardware store. The last time I installed the seal I went with the Dow Corning 737 sealant and it hasn't leaked since. I was able to get the Dow 737 from Ellsworth.com, who happened to be a supplier of my employer. At the time they did not have the small size you would want for a simple seal replacement. Fortunatly they just dropped off a "sample" 12 0z cartrage of it for me to evaluate.:)

In my experience I could tell it was a seal leak by checking the inside of the starter ring, if it is oily it is probably from an oil seal leak.
 
I like to get the bore squeaky dry/clean and a dry outer rim on the seal (that's why I don't like the oil soak). Then I proseal it and let it cure.
 
I just finished (hopefully) a crankshaft nose seal replacement today. For Steve (OP) and others, hope this'll add value to the discussion.

I've also been chasing a pesky oil seep for some time now. Replaced the oil return line on #2, which was wet, but that was not it. Cleaned and inspected the case and sump, ensured all bolts were torqued properly, but no joy. Not too bad a seep, but annoying. One mechanic buddy recently suggested I keep an eye on the front seal (looked OK then...turns out he's a smart guy!)

Then after Reno wrapped up, I uncowled and found this:
IMG_0345.jpg


IMG_0344.jpg


Previously the oil presented itself only around that lower blister, which is under the low point of that part of the engine (James Inlet alternate air door arm recess). This pic clearly shows what was a marked increase in oil spatter, and showed a suspiciously circumferential pattern...right in the neighborhood of the front seal.

The next pic shows the spatter also on the side of the baffle inlet ramp (12 o'clock in the pic):
IMG_0334.jpg


So off came the prop and ring gear, and next, off came the crankshaft timing wheel for the Electroair Ignition. You can see the seal aft of the teeth of the timing CSTW:
IMG_0338.jpg


My seal is a split seal (LW-11997 or SL-11997), as installed by Lycon when the motor was built. It has a single chine that fits in a matching groove on the bore of the case, so I went with matching parts. Saved the stretching maneuver, and fingers are crossed it seals well.

I followed the steps as outlined in a nice article in "Light Plane Maintenance", and it went fairly well. Curing now, so will test it in a couple days. If anyone wants a copy of the article, I'll scan it and send it to ya...just PM me with your e-mail address.

As aerhead mentioned, the article said that being meticulous about cleaning the bore, and ensuring you don't scratch the bore or the crankshaft, are key elements to a successful seal. I hope the 3 hours of cleaning the old pliobond off with MEK and a plastic dowel pay off in a good seal! Its amazing the odd positions one can get your little finger in...between the prop flange and the seal receptacle! :rolleyes: I used pliobond from ACE after comparing it to the pliobond 20 in the nearby engine shop...looked the same, but his was aged past usable...so fingers crossed. More pinky gymnastics, and I had a layer on the inner bore, and one on the seal. If the pressure needed to insert the seal is any indication, that sucker is in there, but good!

All in all, not an overly tough job...just hoping it was done well the first time! ;)

With respect to stretching a one piece seal over the flange, the LPM article shows a couple pics of that, and suggests soaking the seal in "very hot water" before stretching. Just another technique to consider.

Hope all this helps...at the very least it gives you another data point to compare to while contemplating that seal of yours. I'll be one happy camper if this cures my oil seep (or at least this oil seep! ;))

Cheers,
Bob
 
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I changed mine on my IO-540-N1A5. My crank is bigger diameter than other 540's ;) to accommodate a prop spacer or used for aerobatics. This made it harder to put a new one on. I just left the new seal in my pocket to warm it up but I like the sounds of the stove top method. I greased mine up and used a rounded off giant screwdriver to pry mine over the taped prop flange, after removing the spring of course. It wasn't hard at all. I think the hardest parts were cleaning the old glue off the crank case and applying new glue on the new seal while it was on the crank. Mine originally leaked at 90 hours. After replacing mine it hasn't leaked since and now have 430 hours.
 
Hope all this helps...at the very least it gives you another data point to compare to while contemplating that seal of yours. I'll be one happy camper if this cures my oil seep (or at least this oil seep! ;))
Many thanks, Bob. My leak sounds like the very early stages of your now more extensive leak. Given that mine is not yet too bad, I'm going to just keep my eyes on it for the time being, but am definitely bookmarking this thread because there is a lot of helpful info in it! I hope your re-seal job does the trick. Update us with your results would you?
Thanks again.
 
Many thanks, Bob. My leak sounds like the very early stages of your now more extensive leak. Given that mine is not yet too bad, I'm going to just keep my eyes on it for the time being, but am definitely bookmarking this thread because there is a lot of helpful info in it! I hope your re-seal job does the trick. Update us with your results would you?
Thanks again.

Will do Steve. Couple more TLC items and a work trip, then hope to test fly this weekend. Sounds like a good plan for your situation too. My seep was very small for a long time...then it wasn't. It was obvious when action was required. Planes do talk to us! ;)

Cheers,
Bob
 
We had a nagging leak at about 100 hours on my BPEIO540 that was leaving traces exactly like pix in this thread. Same accumulation on the studs of the starter and same soiling on the lower cowl. One really odd symptom was we would see no leak ever on a static runup, but lose roughly the same amount of oil (ounce or two) on a 5 minute flight as a five hour flight. Five successive short flights would make a huge difference over one long flight. Spent a lot of time with Allen on the phone who was very helpful to try and sort it out. I had three different mechanics look at the engine and one rebuilder.

We suspected the prop seal and several other possibilities to no avail. Turned out to be the oil journal plug at about the 2 o'clock position on the front case surface. Those aren't set to very high torque to not strip the threads.

As best the experts have determined, it was set just tight enough that it would appear tight on the cold engine but as it warmed up, the dissimilar metals would allow the plug to leak for a period and then reseal as the thermo expansion caught up. We got lucky enough to catch it one time when it was finger loose even though it was tight when cold.

We reset that plug with the maximum allowed torque and sealant and it has been clean as a whistle ever since.
 
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Where do you apply the sealant on the seal?

Thanks

The details are in the Lycoming SI -

Apply a thin coat of adhesive ( Dow Corning 737 Neutral Cure Sealant*) to the outside diameter of the nose seal and to the inner bore of the crankcase seal bore recess. Do not allow any adhesive to come into contact with the crankshaft and especially the oil return port. If any adhesive comes into contact with the crankshaft or oil return port, use acetone to remove all traces of it.


http://www.lycoming.com/Portals/0/t...I 1324C (05-26-2009)/Crankshaft Oil Seals.pdf
 
Chris
Look at the edge of the prop flange for a part number and serial number. That will give you an idea of what type crank you have.
The constant speed prop has a plug about 4 or 5 inches deep inside the prop shaft. This allows pressurized oil into the CS prop hub. Some CS cranks can be converted to fixed pitch by installing a forward seal that is about 1/2 deep in the crank. When you convert from CS to fixed pitch the rear plug has to be perforated to allow built up oil pressure to go somewhere. Converting back to CS is more difficult as the punctured rear seal has to be replaced.
Some certified aircraft with Lycoming fixed pitch cranks that do not have PID (Painted Inside Diameter) etched on the crank flange have an inspection criteria with hourly requirements. This is due to pitting corrosion found in some cranks.

Thanks for the thought, Chris. My D2A can easily be turned into a D1A for a constant speed prop, so I think I do have a hollow crank, right?

However, would something inside the crank (e.g. inner seal not punctured) cause it to leak on the outside? (Not doubting, I just have no idea what everything looks like inside!)
 
I have been noticing an increase of oil on the belly, and took the cowl off to investigate today.

Lycoming A4M, 350 hours since complete rebuild. Oil consumption, less than 1QT every 10 hours.

I found oil drops pooling on the bottom of the starter and the alternator, and a spray line on the upper cowl around the ring gear. This would seem to fit the other descriptions on this website for defective front seal leaks. The Lycoming bulletin says to look for a cause for the front seal to leak, such as overpressure.

I don't have any kind of air oil separator, so what else should I check for an overpressure source?

What is the likelihood that if it is not due to overpressure that I would have a seal blow out in flight?

Is this something that I should attend to now, or can I wait until the next condition inspection?
 
I have been noticing an increase of oil on the belly, and took the cowl off to investigate today.

Lycoming A4M, 350 hours since complete rebuild. Oil consumption, less than 1QT every 10 hours.

I found oil drops pooling on the bottom of the starter and the alternator, and a spray line on the upper cowl around the ring gear. This would seem to fit the other descriptions on this website for defective front seal leaks. The Lycoming bulletin says to look for a cause for the front seal to leak, such as overpressure.

I don't have any kind of air oil separator, so what else should I check for an overpressure source?

What is the likelihood that if it is not due to overpressure that I would have a seal blow out in flight?

Is this something that I should attend to now, or can I wait until the next condition inspection?

Did you ever get an answer to your question. Was it a bad seal or over pressurization?
 
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