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“Pre alpha” leak

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805HD

Regular Contributor
1975 pre alpha drive randomly started leaking gear lube from the bearing carrier at the prop shaft. The leak appears to be coming out past the main large o ring on the carrier.

Pulled carrier, found a very old and very tired O ring. Replaced that and both oil seals. Held oil for about 24 hours and started leaking again.

Pulled carrier a second time cleaned and inspected bore, looked good. Re assembled using quick silver o ring #8M0214920 and a very light coating of aviation sealant. Pressure tested at 10 PSI, held ROCK SOLID for 20 mins filled with gear lube and it’s now leaking again.

Very small leak but enough to fill the bore and make its way out and onto the ground after a few hours.

Carrier nut is seated to 150 ft/lbs

Any ideas or suggestions appreciated!
 
"""Pulled carrier a second time cleaned and inspected bore, looked good."""

What exactly is LOOKED GOOD?

I have had many drives apart, The surface for that oring corrodes-pitted and/or scale builds up.

I doubt a 1975 doesnt have some kind of crud formed where that oring seals. My 1995 Alpha one gen 1 had the same issue and the surface was ugly. The Aluminum used in 1975 is nowhere as good as newer casting materials so I would say its pitted.

I have had to severely sand that area to get it smooth and I use a TON of Perfect seal goop, Or PERMATEX 80017 AVIATION FORM-A-GASKET #3 SEALANT on the surface and the O ring.

I once did a 20 HP Johnson OB lower I had to sand then use JB weld and recreate a smooth surface thickness to allow the Oring to seal. The surface was so badly pitted.

The only other possibility is the carrier may have a crack

 
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Have you separated the upper from the lower? Obviously you have the 2 units mated during the pressure test.

Oil leaking from the bottom of the upper unit will leak down the exhaust passage and can look like it is coming from the prop shaft bearing carrier o-ring area.
 
Droid said:
Have you separated the upper from the lower? Obviously you have the 2 units mated during the pressure test.

Oil leaking from the bottom of the upper unit will leak down the exhaust passage and can look like it is coming from the prop shaft bearing carrier o-ring area.
Click to expand...
It’s for sure coming from behind the carrier.. I think ghost is onto something..
 
kghost said:
"""Pulled carrier a second time cleaned and inspected bore, looked good."""

What exactly is LOOKED GOOD?

I have had many drives apart, The surface for that oring corrodes-pitted and/or scale builds up.

I doubt a 1975 doesnt have some kind of crud formed where that oring seals. My 1995 Alpha one gen 1 had the same issue and the surface was ugly. The Aluminum used in 1975 is nowhere as good as newer casting materials so I would say its pitted.

I have had to severely sand that area to get it smooth and I use a TON of Perfect seal goop, Or PERMATEX 80017 AVIATION FORM-A-GASKET #3 SEALANT on the surface and the O ring.

I once did a 20 HP Johnson OB lower I had to sand then use JB weld and recreate a smooth surface thickness to allow the Oring to seal. The surface was so badly pitted.

The only other possibility is the carrier may have a crack

Click to expand...
Well, the surface could definitely be cleaner. I’ll pull her back apart and take a better look. I just hit it with scotch brite the picture is what it looked like before cleaning. And good to know I can be a little more aggressive with the sealant if need be.

The weird thing is, how the hell did the drive hold pressure!?
 

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805HD said:
Well, the surface could definitely be cleaner. I’ll pull her back apart and take a better look. I just hit it with scotch brite the picture is what it looked like before cleaning. And good to know I can be a little more aggressive with the sealant if need be.

The weird thing is, how the hell did the drive hold pressure!?
Click to expand...
The O-ring distorts and fits into the area as well as it can, but since the back edge isn't smooth, it may hold pressure for awhile, just not for long.

Use denatured Alcohol to remove the sealant, especially if it was Perfect Seal or something like the Permatex mentioned before. Be careful using abrasives in there.

Better to ensure a flat & smooth surface than assume the sealant will create the seal you need.
 
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