Lycoming Valve Cover Leaks

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Alexb2000

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Alexb2000
My 206 has the TIO-540-AJ1A motor. This is the forth version of the 540 I've had. They all seem to leak out of the valve covers even when close to new. Lycoming uses sloted screws with no safety wire, etc. I always find these very loose whenever I check them.

Anyway, I don't have a consensus for a fix. Several mechanics said change to the rubber gaskets from cork and use regular bolts with safety wire. Others said just replace the cork gaskets.

I've had these issues on brand new motors so I don't think replacement of the cork gaskets makes sense. I also don't want to start changing things from the way the came from the factory unless it really is a poor decision by Lycoming.

What say you A&P's?
 
Alexb2000 said:
Did you stay with the slotted screws? Any leaks with the rubber?

When I say loose I mean less than finger tight.
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yes, my cork ones were welded on, it took me probably 1-2hrs per cylinder to remove the old cork material. I then just went back with the silicon/rubber or whatever the orange spongy ones are. I didn't have any issues for the next 2 years of owning the plane. I don't recall how much torque I put on them per my mechanic but it was tighter than finger tight but I recall being surprised at how little it was.
 
bartmc said:
yes, my cork ones were welded on, it took me probably 1-2hrs per cylinder to remove the old cork material. I then just went back with the silicon/rubber or whatever the orange spongy ones are. I didn't have any issues for the next 2 years of owning the plane. I don't recall how much torque I put on them per my mechanic but it was tighter than finger tight but I recall being surprised at how little it was.
Click to expand...

thanks
 
They leak because they get over tightened. Replace the cork with cork, or rubber, and do not over tighten.
 
Get three sheets of 800 grit wet/dry. Get a decent thickness of window glass. Set the glass flat on the work bench, using some duct tape, tape the wet/dry sandpaper in landscape orientation on the glass, tape the top and bottom. Remove the valve covers, and lay them flat on the wet/dry paper with a bit of water. Press on the center with your fingers, and work the valve cover back and forth across the paper. Keep it wet, and use clear water, maybe a touch of dish soap. When you start, the valve cover will start to look shiny around the holes. Keep sanding until the whole sealing surface of the cover is shiny. I would use cork if it flies regularly, and silicone if it sits a lot. Cork will dry and shrink.
 
BillTIZ said:
They leak because they get over tightened. Replace the cork with cork, or rubber, and do not over tighten.
Click to expand...

Are you saying the factory over tightened them? The issue always seems to be from the screws loosing up on their own. So much so I could take the valve covers off with nothing but my fingers. If you tighten them back up to spec it lasts for a while and then the same thing happens.

docmirror said:
Get three sheets of 800 grit wet/dry. Get a decent thickness of window glass. Set the glass flat on the work bench, using some duct tape, tape the wet/dry sandpaper in landscape orientation on the glass, tape the top and bottom. Remove the valve covers, and lay them flat on the wet/dry paper with a bit of water. Press on the center with your fingers, and work the valve cover back and forth across the paper. Keep it wet, and use clear water, maybe a touch of dish soap. When you start, the valve cover will start to look shiny around the holes. Keep sanding until the whole sealing surface of the cover is shiny. I would use cork if it flies regularly, and silicone if it sits a lot. Cork will dry and shrink.
Click to expand...

I'll check the covers on a surface plate with some dychem whenever I work out the best way to solve this and get the mechanic started on the work. If they are off I'll use your suggestion to flatten them, thanks.

All of them I've had fly a lot ~200 hours or more a year, yet they all leak. I wonder if the cork is not just drying up from the heat of operating?
 
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