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pushrod tube seal leak

DavidHarris

Well Known Member
For the second time in 140 hours of engine operation, I've observed an oil leak that appears to be coming from the #1 pushrod tube seal of my Superior XP-IO360 engine in my Vans RV7A.

I observed a line of oil on the right cooling air inlet baffle, and another line on the top cowling baffle. I also observed a moderate amount of oil on the #1 pushrod tube, especially near the seal, and a fine mist of oil over many parts of the right half of the engine.

After the first leak, I pushed on the seal with my fingers to make sure it seemed to be seated evenly, and kept it under observation. The second leak occurred after the aircraft had been sitting out on a cold ramp for several days. The amount of oil loss is not significant, but it's a hassle to clean and might be advanced warning of a bigger leak.

Is there any leak source other than the pushrod tube seal that would result in this distribution of oil predominantly on the pushrod tube.

How difficult is it to replace this pushrod tube seal? I built the airplane but have no great knowledge of engines. Is this a low-risk job I can do myself, or something where I'm better off doing a warranty claim and taking it to a shop.

Thank you for any insights.

David
 

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That seal is pretty easy to replace, but you have to pull the rocker off first. There is a sticky valve thread that goes into the details necessary to do that.

The relatively large amount of oil you are seeing points more towards a broken pushrod tube holder under the rocker cover. The ECI versions are known for breakage and is made worse if the installer did not determine the correct amount of washers to set the tension properly. Pull the cover and you will see a 3" flat steel piece; The center has a hole for the stud to go through and each side should have an end that is applying tension to the top of the pushod tube. I am guessing that one side has broken off in you case.

If you confim that the seal is not the source of the leak:

I overhauled a 320 years ago and did not realize that there were metal seal holders in the crankcase holes. Between age and the chemical soak likely done by ECI, the glue holding them in broke down and allowed a minor leakage. Apparently ECI didn't pull them and replace them like Divco did for me on the 540.

Remove the pushrod and use a pocket knife blade to pry out the metal cap looking thing. Clean thoroughly and use pliobond to glue it back in. Be somewhat generous with the adhesive, as this is also acting as a sealant. The seal holders are a light press fit, but need something to seal the area.

My leakage from this issue was WAY less than what you are seeing.

Larry
 
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There are two seals, one at each end of the pushrod - very common for the outboard seal (O-ring) to start leaking after a time. But I have found that one of the reasons for these to start leaking is that the clip that holds the pushrods in place looks SS its “spring”. That’s under the rocker cover, and you have to remove it to do anything with the pushrods.

To change the seals, you have to remove the rocker cover, pull the rocker shaft and rocker arms, then take out the pushrods. Then remove the clip and pull the tubes. Replace the seals, reverse the process to assemble. If you turn the engine at all while you’re doing this, you are likely to need to bleed the lifters to get the rods back in, and while that isn’t hard, it takes some tricks you need to be taught.

On the inner seal, they taught us a trick at Lycoming school - turn the seal inside out before installing, and it seals better. Old wives tale? Maybe - but old Jim swore by it....

If you don’t have much Lycoming experience, this is something to be shown by someone who has done it before.

I wrote an article on this whole process recently, but I don’t think it’s gotten in to print yet.

Paul
 
Looks to me more like a crankcase nose seal leak based on all the oil on/between the front ramp baffle.

You could isolate the pushrod shroud seal by cleaning everything up and then wrapping a ~2" wide x 6" piece of cheesecloth around the seal and tube and retaining with electrical tape wrapped around that assembly and then test-flying for a bit. If it makes you feel better, you can also wrap some safety wire around the tube/cheesecloth/tape assembly to hold in place.

If the cheesecloth gets oily and the rest stays clean you found the leak.
 
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Looks to me more like a crankcase nose seal leak based on all the oil on/between the front ramp baffle.

You could isolate the pushrod shroud seal by cleaning everything up and then wrapping a ~2" wide x 6" piece of cheesecloth around the seal and tube and retaining with electrical tape wrapped around that assembly and then test-flying for a bit. If it makes you feel better, you can also wrap some safety wire around the tube/cheesecloth/tape assembly to hold in place.

If the cheesecloth gets oily and the rest stays clean you found the leak.

Possible, but the pic shows the front pushrod tube seal to be substantially less compressed than the rear one, pointing to a broken retainer. Curious to learn the final outcome.

Larry
 
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