found oil on the floor, grounded

[RKellogg]

Originally Posted by Steve Melton

No pictures because I forgot my camera but yes, I had not one but two locations where pliobond was on the shaft under the seal. I'm convinced that was the cause of the seal wear. I don't know how to be more careful with that stuff so the next time around I will use DC 737.

Thanks, Steve!

I really appreciate your thorough, evidence-based study and unbiased reporting. In aviation, as in life, facts work better than opinoin. Thanks!

In mentally preparing for when it is my turn to do this operation, perhaps greasing the strike surface of the crankshaft before applying any sealant, and then applying sealant just to the exterior cylindrical surface of the seal proir pushing the seal into its bore will prevent this type of seal failure.

Tricky operation. Need clean surfaces to allow bonding. Need enough sealant/adhesive to seal/retain the elastomeric seal. Need lubricant between shaft and seal. Grease in wrong place prevents bonding. Excess sealant squeezes out intrnally and drips onto the crankshaft, bonding lip to crank.

Accept my apologies, if indeed that is exactly what you did. You obviously are a thoughtful guy.

Suspect that very fine crocus cloth "cleaning/polishing" of the crankshaft strike surface may enhance seal life. Seal experts tell us that a seal needs to leak a small amount to lubricate the lip/shaft sliding surface for long life. Too smooth a surface doesnt allow any oil to lubricate the seal lip. ... but I deferr to experts.

I still hold Pliobond in high regard for this particular application. No experience with DC-737. Probably should get a tube to see what it does on test coupons.

Please post detail pix when able. ... thousand words...

Thanks for the great post!

[Steve Melton]

no, I didn't add lube to the crankshaft before or this time. it's a tight working space and I didn't trust myself to contaminate the bonding surfaces. it's a personal call.

some tools. stab the old seal and work it out. I also used a wooden trim piece to help push the edges. I heated the seal in boiling water to soften it before stretching. plastic bag to help it slide over the flange. I needed to use small hemostats to hold the spring in order to link it. the tweezers in the photo were not sufficient. applied a thin coat of dow corning 737 to the inside of the crankcase side and then the outside of the seal and put it in wet. if the RTV sets up before install it will not hold, as I was told. I had more control with the application of the RTV than the pliobond I had used on the previous repair.

note: the conduit is the seal stretcher. cut a groove to match the crank flange.

note: MEK used to remove the prior pilobond. my final clean of all surfaces was with brake cleaner

total cost for part, materials and shipping = $50

[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]

[Bill Dicus]

Thanks Steve. Great pics. I'm pulling for an absolutely dry engine...

[scsmith]

I'm having a hard time visualizing how you use the conduit.

I've read the whole thread, but not some of the reference materials that might explain it, so sorry if it is already described somewhere.

[snopercod]

How to Make an Oil Seal Installation Tool

[petercavallo]

I'm not sure if you did but please check your crankcase pressure (use an old oil cap with an AN fitting and an airspeed indicator to find out how much pressure is in the crank case I think max is 5" of water) try in climb decent and level flight

[Steve Melton]

Originally Posted by scsmith

I'm having a hard time visualizing how you use the conduit.

I've read the whole thread, but not some of the reference materials that might explain it, so sorry if it is already described somewhere.

put conduit under the seal. put cut slot on the flange and pull.

[Steve Melton]

Originally Posted by petercavallo

I'm not sure if you did but please check your crankcase pressure (use an old oil cap with an AN fitting and an airspeed indicator to find out how much pressure is in the crank case I think max is 5" of water) try in climb decent and level flight

the vent is open. extra slot cut in the rubber breather tube. the first failure was caused by the white silicon adhesive used at the factory. they don't use that anymore. the second failure was my fault because I used pliobond and some of the pliobond adhered to shaft and wore the seal after 100 hrs. for the third seal I used Dow Corning 737 adhesive. I hope that solves the issue.

no leaks so far.

[sbalmos]

The only leaks you may have is the tent later today, by the looks of the forecast. Coming up tomorrow with the cousin. Enjoy.

[petehowell]

Steve,

Thanks for the step by step on this - great job. I'll be coming back here when I need to do mine.

Enjoy the show!!