PS Magazine - TB 43-PS-688
PS, The Preventative Maintenance Monthly
ISSUE 688
MARCH 2010
10
PS 688
MAR 10
11
PS 688
MAR 10
Dear Editor,
Sitting in the motor pool, our M149A2 and M1112 water trailers are
constantly exposed to the elements. Even though they’re sealed, water can
seep into the brake light housings when it rains.
The seals are still good enough
to hold in that water, so when
it gets deep enough, the system
shorts out.
T
ake it easy on the magnetic drain plug, NSN 4730-00-045-9769,
on your HMMWV’s geared hub when you remove or install it.
The plug already sees a lot of action. The hubs have to be drained
at every semiannual service, before any repair work is done to the
geared hub, and after any operation where water contaminates the
gear oil.
It takes only a little torque
—8-13
lb-ft—to keep the
plug in place. That’s like
Fnger-tight
plus
a
little
twist of the wrench. Too
tight and you’ll strip
the threads.
Use a
3
/
8
-in hex socket
drive to remove the plug.
You’ll round off the plug
head if you use anything
else. That makes removal a
whole lot harder next time.
I
f you don’t apply the HMMWV’s geared hub cover seal the right
way, two things will happen, mechanics. The hub oil won’t stay in,
and water won’t stay out!
Some folks like the RTV
method shown in Para 6-10
of TM
9-2320-280-20-2,
but you’ve got to work fast.
The RTV, NSN 8030-01-
025-1692, will start to cure
as soon as it’s applied.
To make it work you’ve
got to put the cover on
quickly. Then put RTV on
the capscrews and quickly
torque them to 15 lb-ft.
We’ve prevented this problem by
drilling a small
1
/
8-in hole through the
underside of the housing. The hole
drains away any water from rain or
condensation before the lights can
short out.
SFC Eric Mathis
19th Maint
Ft Sill, OK
Editor’s note:
An excellent suggestion, Sergeant. Just
be careful not to hit any of the wiring while drilling.
M149A2, M1112 Water Trailers…
save drowning brake lights
HMMWV…
Don’t Flub
Hub Plug Torque
Keep Oil Where
It Belongs
Rainwater seeps in and
shorts out brake light
Drill
1
/
8
-in hole here so water can drain
UGH!
Will this
rain
never
end?
my brake
lights are
filling up
with water!
not
mine!
my operator
drilled some
drain holes in
my brake light
housing!
here
are some
solutions
for your
HMMWV’s
geared hub
leaks!
Apply RTV here…
…and on threads of all eight screws
Don’t overtighten
drain plug
688.10-11.indd
1-2
1/25/10
6:19:14 PM
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