M

morganjp

Well Known Member
:confused:

I bought a flying RV-6A with a Lycoming 360 A1A about 3 1/2 years ago.
6 months after I bought it; the engine developed an oil leak through the front crank seal. There is a perpendicular scratch on the crankshaft forward near the seal and the oil augers out through the front seal at a rate of about 1 qt. per 4 hrs of flying time. This has been going on for 3 years and over 400 hrs of flight time. Cleaning up the mess is beginning to wear on me and the engine still only has 800 hrs SOH.

Is there any possible fix to this problem short of tearing down the engine and replacing my crankshaft. This engine uses the split seal and I and several A & I 's have replaced the seal numerous times and used some emery cloth on the crank with no success.
Any ideas out there?

John Morgan
 
I don't have a solution. But I'm curious what is your oil pressure is and do you have any pics of this scratch? Sounds kinda weird.

Who built the engine? Was the crank inspected? I assume new main bearings were put in during overhaul.

Chris.
 
I guess it depends on how deep the scratch is for a start..Can you post a photo?

Also you mention it has a split seal..are you sure a lot of the leak is not coming thoug at the split in the seal?

I.e it is worth replacing with a non split type?

Frank
 
There is no good reason to use the split seal in my opinion and whoever told you that you can only use a split seal is flat-out wrong.
 
If its really not that deep and if you can see the end of the scratch with the seal out, I'd fill it with some kind of "miracle metal" and sand it down. At the same time I'd put the proper scratch pattern on the flange as called out by lycoming and proseal in a one piece seal. Squeaky clean the seal bore before prosealing and give it plenty of cure time. Anyone else wanna whack at it?
 
I have no pics at the moment. On inspection the split seal is totally dry when you take off the 2 plates in front of the seal. I am sure the oil is not coming throught the split in the seal. Lycoming says to use the split seal on this engine. Not sure I could get a solid seal on it. The engine came off a 1964 Piper Arrow and was pickled for 9 years after overhaul before the previous owner put it on the plane.

The scratch does not appear to be very deep and I have no clue as to how it got there or why the engine was dry as a bone for 6 months before the oil leak appeared.

John Morgan
 
This from sac sky ranch (hope they don't mind):
Continued problems with nose seals leaking on Lycoming engines may be caused by the fit between the crankcase and crankshaft. If you have inspected the crankshaft seal to confirm the proper type, installation, crankshaft surface finish, crankcase pressurization, but still have a seal problem, then it's time to start looking elsewhere. Buying an exchange or welded crankcase and replacement crankshaft means the crankshaft may not be mated properly to the crankcase. Three subtle engine conditions may make it impossible to seal the crankshaft, These are:

1. Excessive clearance between the main crankshaft bearing and crankshaft journal which allows more oil to leak out of the bearing shell, thereby delivering more oil to the crankshaft oil slinger.

2. A bent oil slinger. As the crankshaft rotates, the slinger wobbles, thereby becoming an efficient oil pump.

3. Not enough clearance between the front slinger face of the crankshaft and the crankshaft nose seal retainer. Lack of clearance will trap oil and sling it forward into the seal. If you have any of these conditions, it requires complete engine removal and disassembly to correct. How do you inspect for these conditions without disassembling the engine?

With the nose seal removed, pull the crankshaft forward. The crankshaft thrust face will now be against the crankcase thrust face. There should now be 2 to 7 thousandths clearance between the crankshaft slinger and the nose seal retainer. Slip a piece of paper in behind the nose seal casting on the crankcase and see if it fits between the casting and the crankshaft slinger. If it does not fit, you do not have the proper clearance. Rotate the crankshaft, making sure it stays forward and see if the clearance oscillates. If it does, the slinger is bent and will pump oil into the seal. If you do not have at least 2 thousandths (preferably not fewer than 5 thousandths) clearance, how do you change it? The Lycoming overhaul manual explains how to grind the face of the oil slinger until you get the proper clearance. Any time you inspect a crankshaft for run-out, also inspect the crankshaft slinger and check the clearance between the slinger and crankcase when you lay the crankshaft into the case during re-assembly.

4. A rare condition may exist where the crankshaft seal leaks or is pushed partially out and there is aluminum in the engine oil. This occurs when there is a failure of the crankshaft thrust face. One cause is a crankshaft who's "white layer" is left remaining on the thrust face after Nitriding. This surface wears into the crankcase bearing surface.




Copyright 1995 by Sacramento Sky Ranch Inc. All rights reserved.
 
The breather tube is fine. The oil pressure is about 80 PSI. The oil filter inspections show no metal. With the last seal install we looked at the clearance in front of the crank and it was ok or at least the mechanic said it was ok.

What is miracle metal and where do you ge that?
 
I was just talking about any of the liquid metal, epoxy, JB weld type stuff. Also put a new scratch pattern on the shaft with like 320 grit that spirals in the right direction. None of that will help though if you've recently increased blow-by, have an obstruction, or maybe an oil pressure change.
 
No change in oil pressure. I don't remember the exact clearance that was measured. He just said it was ok.
 
morganjp said:
I get no oil at all in the breather tube
Click to expand...

It is very normal to have oil in the breather tube...... a fine mist that you can wipe off with your little finger. Tape a clean tube to the breather tube and blow into it with your mouth to see if it is clear.

Don't use proseal.................. PLIOBOND is used on this seal.
 
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Crankcase pressure

I'm thinkin' you might do well to hook up a gauge to the crankcase, and check the pressure. A pressurized case can force oil out the front seal.

Search VAF or Sacramento Sky Ranch, or the web for how to measure crankcase pressure.

If your breather outlet is in the wrong location, or is scarfed to provide positive pressure, you might have excess pressure in the crankcase.

Actually measuring the pressure in flight should tell the tale.
 
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