[VAL] Dump Valve in 1960 Pacer - Followup

[John Sellers <sellersj@xxxxxxxxxx>]

Gang,

About a month ago I posted some questions about overhauling the leaky
sewage dump valve on my 1960 Pacer.  Thanks to all of you that responded
on- and off-list.

I managed to fix the valve, so I thought I might document my experience
for the archives.  This post will be rather lengthy, but may save
trouble for anyone who comes across a similar valve.

Sewage holding tanks were apparently a new thing in 1960.  Ed Emerick's
1959 Traveler, for example, didn't _have_ a black tank.  Airstream must
not have settled on a standardized dump valve yet; I have never heard of
another one like they used in our Pacer.  (Although the same valve might
turn up in some other 1960 models.)

The dump valve in our Pacer is a two inch bronze "wedge gate valve".  In
other words a gate valve with a tapered gate that wedges in between two
mating seats in the valve body.  The seal is metal-to-metal; there are
no gaskets or O-rings other than the packing around the valve stem.

In my first post I noted that the valve seemed to be in good shape, no
external leakage or corrosion, but I had unscrewed the valve bonnet but
couldn't get the gate out.  The valve would neither close nor open all
the way.

First, the secret of getting the valve apart.  The valve is operated by
the usual push-pull aluminum T-handle sticking out the side of the belly
pan.  The T-handle appeared to be permanently affixed to the valve stem;
no clips, pins or setscrews in sight.  It dawned on me that the valve
stem might _unscrew_ from the gate if the square-shank T-handle was free
to turn.  The T-handle sticks through a rectangular hole in a little
aluminum plate riveted to the belly pan.  Drilling out the rivets to
free the plate uncovered a larger round hole in the belly pan, leaving
the T-handle free to turn.  Turning the T-handle unscrewed the stem from
the gate, allowing the valve stem and bonnet to be removed.   (It's a
left-handed thread.)

With these parts out of the way I could see the gate, although I still
couldn't see why it was jamming in the valve. But it looked like it was
supposed to come out.  At that point I adopted an Attitude--frequently
necessary in dealing with old plumbing fixtures.  Specifically, "THAT
@#$% GATE IS COMING OUT ONE WAY OR THE OTHER!"

Between the Attitude and a liberal dousing with Kroil, the gate came out
with relatively little force.  The problem was immediately obvious.  The
gate is a hollow bronze casting, relatively thick; about a half an inch
at the inner edge and an inch at the outer edge.  At some point water
had gotten into it and frozen.  The casting was bulged and actually
cracked in one place.

As bad as it looked, the gate casting was repairable, owing to the
wonderful malleability and solderability of bronze.  First I boiled the
part in a stiff detergent solution to remove accumulated filth, followed
by a short soak in muriatic acid to brighten it up.  Then I restored the
mating surfaces to approximate flatness by careful hammering and filing,
testing frequently against a surface plate with hi-spot blue.  By the
time the surfaces were reasonably flat the crack had closed up, so I
filled it with solder.

Next I took the gate and the hi-spot blue out to the trailer and
hammered and filed the gate surfaces some more to fit them to the seats,
which, after all they had been through, were probably not all that flat
either.  I was pleasantly surprised to achieve metal-to-metal contact
about 80% of the way around both seats.  (Not unexpectedly, the gap on
both seats was where I had dragged the swollen gate over them.)

Even after 44 years the valve bonnet had a lot of grease in it and I
began to suspect that the grease was what was supposed to make the whole
thing work.  An Internet search on "gate valve" AND "grease" hit pay
dirt.  It turns out that some metal-to-metal wedge gate valves use a
specially-formulated sealant/grease to both seal and lubricate the
valve.  The oil industry must use a lot of them because the distributors
selling valve sealants were all in oil country.

I settled on Nordstrom 386 sealant, which is recommended for water and
sewage service.  I bought some from A & J fittings, www.ajfittings.com ,
877-453-4333 in Houston, Texas, who were friendly, helpful, took charge
cards, and had the stuff in stock.  The smallest quantity I could buy
was a six-pack of grease gun packs--more than a lifetime supply for one
Airstream--but, I figured, cheap enough if it solved the problem.

When I received the Nordstrom 386 sealant I reassembled the valve,
packing the gate casting full before installing it and then filling the
valve bonnet before I screwed it down.  That sealant is about the
consistency of peanut butter, and just as sticky.  And it works great! 
I could scarcely believe it when I filled the black tank with water and
the valve didn't leak a drop!

Since then I have filled and dumped the black tank several times and the
dump valve continues to be leak free.  I suspect to keep it that way it
will be necessary to unscrew the valve bonnet once a year or so and
stuff in some more sealant.  Aside from that slight need for
maintenance, the 1960-model dump valve seems to work pretty well.

Best,
John Sellers
WBCCI/VAC #1587
1960 Pacer
Dayton, Ohio