Crankshaft Seal Question

[Tom G]

My front seal has decided to start leaking. I've checked the crankcase vent and its clear so its definitely a bad seal. I've ordered a new one and will soon be installing it. I have the flange shaft and not the tapered one so I know its a bit more difficult. I have a friend with a hangar with every tool imaginable so thats not a problem. My question is have any of you done this job and could you tell me how long this might take. My cousin who is very mechanical is going to help me as is a friend of mine who has built a number of airplanes but hasn't done this job in many years.

Is this a job that can be done in a day? Any hints as to just what tools will be needed. When I look at the flange it sure looks awful close to the front of the engine. I'm not known for having an abundance of patience so should I go off and have a beer and pay someone to do it???

Any advice would be appreciated. Thanks!!

[Ron Babos]

Re: Crankshaft Seal Question

Tom G: If you know what you're doing it takes less than an hour. First time it may take a little longer.
You need to carefully pound a flat screwdriver blade just through the face of the old seal. Place a piece of wood between the case and the screwdriver and start prying the seal out. When out remove the spring inside the lip and take the seal off the crank. Clean the case out where the seal sits of any old glue and oils.
On the new seal remove the spring and twist the seal only enough to slide it over the crank with flat side out.
Hook the spring up inside the seal lip and put a light coating of aviation gasket goo on the perimeter and inside the case . Just a very light smear is all you want. Don't get any on the crank or seal lip. Before doing this, find a couple of wood pry bars that will push the seal in while using the back side of the hub as the pivot point for the wood bars.
Lightly oil the crank where the seal lip will go. Place a very small amount of permatex in the seal joint. Just a light smear again.
Line the seal split at either 11 or 1 oclock . Never inline with case split.
Slowly start pushing the seal in at the bottom first, and work your way up with the wood. Remember there's a spring in there that you don't want to come off, so don't twist the seal around too much. Once you get the whole seal started it the hole about 1/8" all the way around you have the idea and just slowly keep working it until it's all the way in , 1/16" at a time. Make sure the seal joint is matched at the line and your good to go.
This works for me, but others may have found other methods that work for them as well.
Ron

[NY86]

Re: Crankshaft Seal Question

Ron pretty much covered it. I'd only add to position the joint in the spring 180 degrees from the split in the seal. Alos, cleaning the case bore is very important. Any oil on the case will keep the new seal from sealing correctly.

[Tom G]

Re: Crankshaft Seal Question

Ron and John: thanks very much for the advice. I've ordered the seal from aircraft spruce. I'll let you know how it goes.

[larrysmith1016]

Re: Crankshaft Seal Question

In a BC12D I have an A-65-8F. It leaked around the seal. So I replaced it. It still leaked. So I replaced it again, but not until after cleaning up the tiny little bit of scoring on the crank. Then I used that old service letter some of you know about and some 320 grit and put a little 45 deg. angled surface on the crank per the SL. Oil is now screwed back into the crankcase, and the seal has never leaked since. And yes, the A&P was looking over my shoulder.

This engine has over 200 hours and it doesn't leak anywhere except for a few drips out the breather hose. And I can fix most of that too, as some of you old-timers know, with that Cessna Aerobat elbow extension in the crankcase. One of these days I'll do that too.

A couple of years ago, the engine started to make a little blue smoke. Compression was still high, but I did a top by honing the cermichrome cylinders and installing new rings. Seats and guides were great. Now after break-in compressions are all in the high seventies, and she doesn't make any smoke. She uses a quart of oil every 10 or 12 hours, and that suits me. Plus she makes plenty of smooth power at static run-up.

One thing I did notice, which was a little weird. With standard pushrods, one of the lifters had dry clearance which was too tight. I had a few thousandths removed from the exhaust valve stem and she lined up within tolerance, which is .030 to .110. This was a first for me and my A&P. Usually dry clearance is too loose, as in an engine we just finished where we had to install two pushrods which were .030" over.

What a sweet running little engine she now is.

[crispy critter]

Re: Crankshaft Seal Question

I would put my 2 cents worth in but it seems as if all the bases have been covered.Good luck and have some beer on stand by just in case. It is one of those jobs that is very simple once you've done it a time or two or watched someone else do it but the first time solo can be a little rough.Take your time and don't rush it.

[Tom G]

Re: Crankshaft Seal Question/ Go figure

I flew my plane today to check and see the severity of the leak. Before I took off I cleaned off everything . I did two takeoffs and landings and when I stopped everything was still bone dry. I took off again and flew around the local area for about 30 minutes. On the way back I did notice a very slight mist on the windshield but now only on a small part of it instead of the whole thing. When I got down and checked it out everything was still pretty dry. Nothing approaching the streak of oil I found on the nosecowl last time. It looks like the oil is coming from between the prop and the flange on the back of the prop. Anyway, I'm going to replace the seal but it doesnt look like the emergency I thought it was. I don't see how but can these things come and go???

[Guest]

Re: Crankshaft Seal Question/ Go figure

I flew my plane today to check and see the severity of the leak. Before I took off I cleaned off everything . I did two takeoffs and landings and when I stopped everything was still bone dry. I took off again and flew around the local area for about 30 minutes. On the way back I did notice a very slight mist on the windshield but now only on a small part of it instead of the whole thing. When I got down and checked it out everything was still pretty dry. Nothing approaching the streak of oil I found on the nosecowl last time. It looks like the oil is coming from between the prop and the flange on the back of the prop. Anyway, I'm going to replace the seal but it doesnt look like the emergency I thought it was. I don't see how but can these things come and go???

Hi Tom,

Maybe the temperature of the seal effects it?

Softens up with temperature?

Dave

[NY86]

Re: Crankshaft Seal Question

Tom:

you should check your crankcase pressure. PM me if you need a copy of the relevant SB.

[Tom G]

Re: Crankshaft Seal Question

I don't know why but for about the last 4 hours the leak has been practically non existent.......for what the leak amounts to now I wouldn't even consider replacing the seal.

[Guest]

Re: Crankshaft Seal Question

Hi Tom,

What changed? Do you know?

Dave

[Tom G]

Re: Crankshaft Seal Question

Dave: I wish I could tell you. Nothing I can think of.