\?JILI.YS MODEL
"MR"
%-TON
4
x
4
COVERNhlENT TRUCK
8500-53
COOLING
SYSTEM
The satisfactory performance of an engine
is
controlled toa great extent by the proper operation
of the cooling system. The engine block is
full
length water jacketed which avoids distortion of
the cylinder
walls. Llirected cwliiig and large water
holes,
properly placed in cylinder head gasket,
cause more water to flow past the valve seats (whicli
is the
hottest part of the block) and carry tlie heat
away from the
valves. giving positive cooling of
valves and seats.
To quickly
warm up the engine and hold the cool-
ing fluid to the maxinium efficient temperature,
there is a thermostat installed in the
tvater outlet
on the cylinder head.
Radiator
The radiator is designed to cool the
water under
al1 operating conditions, however, the radiator core
must be kept free from corrosion and scale in
addition to tlie maintenance of otlier cooling units
to obtain satisfactory service.
At least
every
20,000
miles remove the radiator
and clean it
inside and out in a cleaning
solution. At the
Same time examine core for leaks
or damaged cells.
After radiator and cooling system liave been
cleaned and flushed out. it is advisable to use a
corrosion preventative. Rust and scale may
even-
tually clog up w.ater passages
in
both the radiator
and water jacket of tlie engine unless a rust in-
hibitor is used. This condition is aggravated in
some localities by the water available.
Emergency repairs in case of puncture by bullet
or shrapnel; if a tube is not completely severed.
cut it or break
it
off with a pair of pliers. With
pliers strip
Fins from tube above and below break
lor
w
or necessary distance to enable bending of
the tube around
itself and flatten, both above and
below the break tliereby stopping the
AOW
of water.
Radiator
Flller Cap
Tlie cap
is
of tlie pressure type which prevcnts
evaporation and loss of cooling solution. A pres-
sure up to
3%
to
4%
pounds makes tlie engiiie more
efficient by
riinningat a slightly higher temperature.
Vacuum in the radiator is relieved by a vacuum
valve opening at to
1
pound vacuum.
Draining Cooling System
To drain tlie cooling system open tlie drain cock
located at the luwer
left hand corner of tlie radiator,
just under the water
outlet, also the drain cock
at
right front lower corner of cylinder block.
Remove radiator cap to break any vacuuiii and
thoroughly drain system.
Filling the Cooling System
Close drain cocks in thc cylinder block and
radiator.
Fill the radiator, with clean water or
during cold
weather with an anti-freeze soliition.
Do not overfill the radiator while anti-freeze
solution is being used, because the solution expands
when heated
aiid an appreciable anioiint of liquid
would be lost throiigh tlie overflow. 'I'lie solution
sliould be
1"
from tlie bottom of ilie filler neck.
Sliould water be lost from the cooling system
and the engine overheats, do not add water
im-
mediately but allow tlie engine to cool, then add
water
slowly while the engine
is
running.
If cold water
is
poured into the radiator while
the engine is overheated, there
is
danger of crack-
ing the cylinder block and head.
Thermostat
Tlie cooling system is designed to
provide
adequate cooling under the most adverse
conditions; Iiowever, it is necessary to employ
some
device to prevent overcooling during normal
operations. 'I'his is accomplished by use of a therm-
ostat, (No.
39.
Fig.
1,
"Engine" Section) which
is
located in the water outlet on top of the cylinder
l
..
.
---..p.
..
~
FIG. I-\VATER
PUMP
AND FAN.ASSE.?IBLY
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