prop seal

Well, after only putting 12 hours on our Aztec since our annual, we've got a
bad prop seal on our left prop. The prop shop is overbooked until OSH is
over, so we've got it scheduled to go in Aug. 3. (One side benefit is that
while the prop is gone we'll have time to put in our new side windows!

The prop has 985 hours since overhaul, 8 years ago, with a recommended TBO
of 2400 hours or 6 years.

What happened? Most likely we over greased it at annual and then last
Sunday in 98 degree heat, the pressures in the prop were high enough and the
grease was thin enough to leak past the weak seal. We knew the seals were
weak, as there was a slight amount of grease at the roots of the blades, but
now it's being flung out over 3/4 of the length of the blades.

A couple of interesting things that we've learned.

1) For aluminum hubs, Hartzell no longer recommends simply pulling one
grease zirt then pumping grease into the hub until it exits the open zirt
hole. Now they recommend to pull one zirt and pump grease until it either
begins to exit the open zirt hole or after adding a maximum of 1oz of fresh
grease, whichever comes first. It's still important to remove on zirt from
each side of the hub before adding grease to prevent pressure from building
in the hub.

Why? Our prop shop says that they've been getting at least 2-3 props per
month that are still under warranty that have been over-greased and the
seals have blown. They say that they've been complaining to Hartzell about
the old greasing procedure for years, and they've finally addressed it.

2) Another thing that we learned is about Hartzell's recommendation to use
Aeroshell #6 grease. Our guys say that in warmer temperatures, it's simply
too thin, they absolutely cuss at it. For most GA piston engine airplanes,
our shop says they normally use Aeroshell #5 even though it's prohibited
from use at temperatures below -41F (placarding required). Hartzell uses #6
because it is a more "general purpose" grease, has a broader temperature
spectrum, and without knowing specifically the area their props will
operate, they feel it covers the most bases. I don't know about you, but we
rarely fly in temps below -41.

The shop we're using, Maxwell Aircraft, has been in the propeller business
since the 1940's, so they should have enough experience to know what they're
talking about.

Any comments or experience is greatly appreciated.

Jim