diagnosing propeller leaks

I got grease coming out of my Hartzell Constant speed prop and it was on a hot day. Prop shop inspected it but said it was just a "burp" and all I had to do was wipe it up and go on my way. Said "they sometimes do that" and "they get a bubble and it because its a hot day it forces the grease out the zert the opposite direction and that is what is supposed to happen so the seal doesn't go". Felt a little weird, but he was the prop shop owner so I believe it. Talked to the factory test pilot and he is an IA too and he concurred. YMMV.
 
I've gotten the same response for our Dakota.
 
I've never seen a grease zerk that was designed to allow reverse flow... Every one I've seen is a one way check valve. Here is a cut away drawing of one style:
104004d1342635770-grease-nipple-lower-ball-joint-grease-fitting.jpg
 
I've always looked at the back of my prop and also run my hand on the back of the prop to look for oil.

Only ones I've seen leak

A fresh prop on a 550, just was a little shiny on the back, nothing you could see/feel on your hand if you touched it, went away over a week and all was well.

A rental senica in CA, VERY noticeable on one side, CFI said he had no idea.... Also it had a major sketchy ass school vibe, never ended up using that POS.
 
Craig said:
I've never seen a grease zerk that was designed to allow reverse flow... Every one I've seen is a one way check valve.
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Agree. At the very least, that zerk should be replaced. They can corrode, or have a manufacturing defect, and give a small path for grease to flow.
 
I've seen a minuscule amount of oil seep out after shutdown a few times. Seems to be after longer flights. Doesn't sling oil in flight. Not getting worse, but not getting better, either. Tempted to try leaving the prop horizontal vs. one blade low vs. the other blade low.
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GeorgeC said:
I've seen a minuscule amount of oil seep out after shutdown a few times. Seems to be after longer flights. Doesn't sling oil in flight. Not getting worse, but not getting better, either. Tempted to try leaving the prop horizontal vs. one blade low vs. the other blade low.
View attachment 46132
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What if it was a three blade?
 
The article is 100% what Hartzell espouses and what you need to do in practice. You must REMOVE one of the grease fittings and feed grease into the other one until you see it start to come out the other hole. If you don't do this you'll blow grease out the seals for some time to come. Even the non-Hartzell shops (Sennsenich) warned me of this on my prop.
 
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