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IO-390 prop or crankshaft seal leak

Clipper1

Active Member
I have a little oil leaking from the front of the engine. I'm thinking it is either coming from the prop seal or the crankshaft seal. Is running the engine ok to do or is there a concern that you could blow out either seal? I'm not sure how either seal is secured in and so I am unaware how much risk there is and therefore figured I'd ask.

TIA
 
How much oil is it and where do you see it.
If t is the prop, you should see it on the back of the blade.
If it is the crank seal, it may have traces of it by the seal

Please note that it is possible that is coming from engine area and getting blown out from the gap between the prop and the cowl
 
I have a little oil leaking from the front of the engine. I'm thinking it is either coming from the prop seal or the crankshaft seal. Is running the engine ok to do or is there a concern that you could blow out either seal? I'm not sure how either seal is secured in and so I am unaware how much risk there is and therefore figured I'd ask.

TIA

Leakage from the Crankcase Nose Seal is usually a messy affair with engine oil dribbling out and down around the inside of the cowl, the top and bottom of the case, etc. etc.

Prop seal leakage is usually evidenced by greasy "streaks" emanating from the hub/blade root and extending along the back side of the blades.

By any chance did your propellor sit for a long time before installation and usage?
 
Thanks!

It is not showing along back of blades. I'm seeing it appear from behind the spinner. When I remove the cowl I see it mostly showing on the back of the starter ring gear.

I don't believe the prop was sitting still for long.

appreciate all the help!
 
Thanks!

It is not showing along back of blades. I'm seeing it appear from behind the spinner. When I remove the cowl I see it mostly showing on the back of the starter ring gear.

I don't believe the prop was sitting still for long.

appreciate all the help!
Check your crankcase vent. Could be causing crankcase pressurization if blocked.
 
I had this and started using camguard and it helped, not sure why. I still see a bit of oil on the inside of the ring gear from time to time, but often it's bone dry. Not 100% it's the nose seal, but most likely.
 
Be careful, if the nose seal goes in flight, you are going to lose all the oil quickly.
It is glued in and not hard to replace.
 
Thanks!

I've read somewhere people say it can spin too which can cause an issue. Glue alone seems like an oversight. I guess anyone's could 'pop' out at anytime then?
 
If the rear inner surface of the flywheel pulley is wet, than it’s most likely the front crank seal.
If there are wet oil streaks on the front face of the flywheel, it is the prop flange o-ring seal.
Either way, the prop is coming off… & be sure to put a new o-ring on the flange before reinstalling that prop.
 
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A bad seal around the crank will definitely be a mess. I had an engine overhauled and they milled the case and I think, stamped it on the outside of the case. They installed a standard size seal and it leaked. Took it back and it was better, but still had issues. The third time was the charm.
 
The engine has 400 hours on it TTSN (3 years). Is this a problem that sometimes has no specific cause? Assuming the breather line is not blocked.

I assume that sometime the glue around the seal fails and this causes it to leak a little. I've noticed that on the io540 it has a plate covering this seal. I wonder why they didn't do this on the io360/390 engine??
 
I have a little oil leaking from the front of the engine. I'm thinking it is either coming from the prop seal or the crankshaft seal. Is running the engine ok to do or is there a concern that you could blow out either seal? I'm not sure how either seal is secured in and so I am unaware how much risk there is and therefore figured I'd ask.

TIA

FWIW I had to replace my crankshaft seal a few months ago with less than 200 hours on it. I called Lycoming and they said its pretty common on the new motors because the EPA made them change from Pliobond to a "greener" adhesive. Even though the calendar time was over they gladly covered the part and labor under warranty. Instead of the one piece seal that came from the factory I elected to install the split seal. Reinstallation (used pliobond) was cake once the prop was off.
 
I actually managed to get my hand and fingers around the starter ring today and could fell the seal. When I moved the prop I could also feel the seal turning, which I'm sure it shouldn't?

Using my fingers I felt it 'click' when I pushed it back and then I went and flew the pattern. No oil at all right now. I've got a spare part and I'm going to change it. Is Pilabond better then Dowling 737?
 
I actually managed to get my hand and fingers around the starter ring today and could fell the seal. When I moved the prop I could also feel the seal turning, which I'm sure it shouldn't?

Using my fingers I felt it 'click' when I pushed it back and then I went and flew the pattern. No oil at all right now. I've got a spare part and I'm going to change it. Is Pilabond better then Dowling 737?

I’ve always used PlioBond, and never had one break loose inadvertently - just make surer every surface is surgically clean before you re-install. You can find a write-up on the entire process at:

https://www.kitplanes.com/maintenance-matters-45/

Whatever you do, please DON’T fly the airplane again with the seal in the condition you described - you can easily blow it out if its not glued in place, and then you lose the entire engine oil load pretty fast - its a mess, even if you’re in the pattern when it happens! If you’re not in the pattern, start looking for a cornfield……
 
This is an EXCELLENT article. Just what I was seeking out. Also, I feel a little embarrassed that I flew today too.

I cannot tell you how much this information helps. it REALLY is appreciated.
 
I've chased a bunch of chronic leaky nose seals in my time, so I guess this is a good place to pass along some hard-earned knowledge. For chronic leaky seal situations, consider these two mods.

If your seal has spun, and you're confident it was installed clean and bonded well, you might consider using Proseal. Everyone I mention this to says, "OMG! You'll never get it out." Not true. It bonds very well, yet is still removable.

If your seal stays bonded, but still leaks, I suggest shortening the spring by ~3/8 - 1/2 inch. To do this, just cut off the appropriate amount from the loop end of the spring. Bend over two new loops 90-degrees to the spring and attach as normally intended. Will provide more sealing force.

I've done this on quite a few seals over the last 10-15 years and never once spontaneously combusted or perished mysteriously, yet.

Last, someone mentioned the "retainer plates" on the nose. The newer engines casings are generally cast to accommodate these. Some are drilled and tapped (1/4"), some not. And some of the older casings have drilled and tapped smaller holes (3/16"). So, it varies. But I do like having these plates installed.
 
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