Engine Water Jacket and Cylinder Head
External coolant leakage may occur at any of the
joints in the engine water jacket such as the drain
plugs, core hole plugs, or cylinder head joint. Since
expansion or contraction can aggravate leakage, the
block should be inspected both hot and cold while
the engine is running.
Internal leakage occurs when coolant passes into the
engine oil through a loose cylinder head joint or a
cracked or porous casting. The leakage is not visible
but may cause extensive damage to the engine. Cool-
ant mixes with the oil to form sludge which causes
lubrication failure. Heavy sludge accumulations fol-
lowed by sticking piston rings, valves, and tappets are
symptoms of internal leakage.
Sometimes internal leaks are small enough to prevent
coolant leakage but permit exhaust gases to enter the
cooling system. The exhaust gases dissolve in the
coolant, depleting the rust inhibitors and forming
acid which causes corrosion.
Thermostat
Replace thermostat if
it
is broken, corroded, or sticks
in the open or closed position. If engine overheats or
does not reach and maintain a minimum operating
temperature, the thermostat should be removed and
tested as a possible cause.
1. Remove thermostat from cylinder head.
2. Heat a pan of water to approximately 150°F.
Check temperature using a thermometer im-
mersed in water.
3. With thermostat suspended in water at tempera-
ture of 150°F, thermostat should start to open.
4.
After thermostat has opened completely, remove
it
from hot water and allow it to cool in surround-
ing air. The thermostat should close within a
short time.
5.
If the thermostat sticks or does not operate prop-
erly, replace
it
with'a new one.
6.
Always install a new gasket when replacing the
thermostat.
Draining Cooling System
Whenever draining the cooling system for changing
anti-freeze solution or for out-of-service protection
when only water is used, be sure to open all drains
and hose connections where water could be trapped.
Contact with hot coolant might
result in serious burns.
Do
not bleed
hot, pressurized coolant from
a
closed cooling
system.
The following drain plugs must be removed to allow
complete flushing of the cooling system.
Radiator:
One petcock lower right front corner.
Engine
Block
One drain plug left front near water
Pump.
Water
Pumps:
One drain plug under cover or by
loos-
ening cover.
If
an optional water jacket tank heater
is
used it should be drained
and flushed also. The lower hose must be disconnected at the tank
heater. There is no drain plug.
After making repairs on the cooling system, tighten
all connections thoroughly. Use Permatex or thread
sealing compound on all threaded connections to
prevent leaks or the entry of air into the system.
Read instructions on Permatex Sealer can before applying sealer
to engine parts.
Pressure Cap
The pressure cap increases the boiling point of the
coolant by allowing pressure to build up in the cool-
ing system. The increase in boiling point reduces the
chances for coolant loss due to boil over. A 15 psi
(103.5 kPa) pressurecap will raise the boiling point of
water to 250°F (122°C) and the boiling point of a
50/50
mixture of water and anti-freeze to 265°F
(132°C). Pressure caps should be inspected periodi-
cally for freedom of operation and the gasket should
be checked for proper sealing. Replace the pressure
cap if it malfunctions.
17
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