Bent push rod causes oil leak

[MooneyBob]

I always found few drops of oil under the plane after flight. I was told it is normal and it is oil blown from the breather. It really annoyed me. I have removed the cowling few weeks ago for the first time as I have no experiences with the planes engine or mechanics at all.

I noticed that there is an oil stain on the top of the cylinder. Not a big deal, I was told.

I didn't feel like flying today so I removed the cowling again and took a closer look. It looked like the tube that houses the push rod is kind of loose or somethIng as it was really easy to spin it around. And it looked like the oil is coming from the spot where the tube enters the head of the cylinder. So as I am turning the tube a little more I have noticed that is bent. Since it's bent it is shorter and that's why it doesn't sit properly, seal is all messed up and tune oil leaks from the cylinder head.

I was wondering what could cause the tube bent like that. I called my mechanic and he said that pushrods is bent too and it happens when the exhaust valve (on cylinder 4 ) gets stuck. So I took it apart and I pulled the pushrods that is really bent and is rubbing against the tube inside. Pretty scary to me.

I have this plane for 8 months ( my first plane ever) and I put 120 hours on it. It had new engine with 485 hours but it was flown very little last 10 years.

I have to say that I never noticed any performance issues or change. No clicking or strange sounds, performance very close or right on the numbers according to POH. I have no idea when it could happen. Maybe very first time the plane was started after sitting long time? I don't know.

Before I removed the push rod I have turned the prop few times around to see that the valve is working properly. It looked like it travels freely all the way up and down.

My questions:

1.What causes the valve gets stuck? Again, it is exhaust valve on #4 cylinder.

2. What would be the concern after I replace the push rod and tube? Should we take a closer look at the valve or take the top apart to see any possible damage?

[tony]

Kind of a common problem of Lycoming engines.  You have to find out why the valve is sticking.  You probably should perform the wobble test.  Your mechanic should have the equipment to do this.  Here is some background information you might find useful.

 

 

http://www.tennesseeaircraft.net/422/