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HELP!!! Onan in 1978 AC720 throwing oil...

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Please give me some advice...

The Onan 19.5hp engine in my 1978 AC720 has started throwing oil.  I bought this tractor new and it is like one of my children.  In the mid 80's I had to have the engine rebuilt because the oil pickup tube fell off and the engine of course, locked up.  I have had no major issues with it ever since.  (I did put an electric fuel pump on it a few years ago.)

I can turn a wrench, but when it comes to rebuilding an engine, I'm not sure I could do that.

The oil seems to be coming out around the pulley on the front of the engine, as you can see from the pictures.  I have run the tractor three times for about 20 minutes since I first noticed it throwing oil and each time I run it, it seems to throw a little more oil.

The picture from the side showing the timing marks was taken the first time I noticed it throwing oil.  The second picture was taken the last time I ran the tractor.  You can see quite a bit more oil this time.

Will you guys please give me some advice?  Is this the death sentence for this engine?  I am willing to attempt to pull it out and work on it...if you guys will walk me through the process.

Any advice is greatly appreciated!!


Throwing oil.jpeg

Throwing oil #2.jpeg

Name plate.jpeg


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Could just be the front seal, hard to tell from the picture. Need to get the clutch off so you can see. Think there might also be a front bearing plate that would have a gasket that could leak on that engine. Both pretty easy fixes. 

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Nothing is ever a death sentence to these unless fire or bad trauma.

Looks to me like your crank seal is shot.  remove the clutch & see.  Shouldn't be too hart to remove & replace.  thread a couple small screws into the metal ring of the seal & use a screwdriver to pry out.  Clean & de-bur shaft so it looks like a mirror.  Cover the shaft with plastic wrap to protect the seal when installing the new one.  Use a correct size & length piece of tubing on the seal & tap in with a hammer.  If the seal is completely "blown out" of its place, then I would suspect your rings have wore again causing an increase in crank case pressure.  

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Check the crank case breather on top of the engine as well. If it's plugged, the engine can build pressure internally, forcing oil out of places it shouldn't...a lot easier to check that first than start tearing into the engine.

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