MOTOR TRUCK SERVICE MANUAL
If clogging of core is relieved but not fully
The cooling system of any truck should be drained
corrected, allow the engine to cool, pressure
and flushed out at least twice a year. Unless the cooling
flush the system (See Pressure Flushing) and
water or antifreeze has a corrosion preventive, rust and
repeat cleaning operation.
scale will eventually clog up the cooling system. If no
8. If clogging of core, indicated by low temperature
recommended cleaning solution is available when
spots on core, is not relieved, radiator core must
cleaning the system, dissolve four pounds of washing
soda in water and fill the complete cooling system.
Mechanical cleaning requires removal of upper
Leave the radiator cap off and run the engine until it is
and lower tanks and rodding out the
hot. Then disconnect the radiator outlet hose so all
accumulated rust and scale from the water
sediment will pass through the drain cock and flush
passage of the core.
thoroughly with clean water. NOTE : Remove radiator
1. Disconnect the upper radiator hose which
cap when draining system to as sure proper draining.
connects radiator core to engine water outlet and
1. Coolant shutoff cocks to heaters and other
remove thermostat from engine water outlet.
accessories should be open to allow complete
2. Clamp a convenient length of hose to the
circulation during cleaning, flushing and draining.
radiator core outlet opening, and attach another
Run the engine with radiator covered if
suitable length of hose to the radiator inlet
necessary until temperature is up to operating
opening to carry away the flushing stream.
Stop engine, remove
3. Connect the flushing gun to compressed air and
radiator cap and drain system by opening drain
water pressure, and clamp the gun nozzle to the
hose attached to the radiator outlet opening.
2. Allow engine to cool, close drain cocks and pour
4. With radiator cap on tight, fill core with water.
cleaning compound into radiator according to
Turn on air pressure in short blasts to prevent
directions. Fill system with water.
3. Place a clean drain pan to catch overflow, and
5. Continue filling radiator with water and applying
use to maintain level in radiator. Do not spill
air pressure as above until the water comes out
solution on vehicle paint.
4. Replace radiator cap and run engine at
6. Clamp the flushing gun nozzle firmly to a hose
moderate speed, covering radiator if necessary,
attached securely to the engine water outlet
so that radiator core reaches a temperature of
opening. Fill engine block with water, partly
180°F. or above, but does not reach the boiling
covering water inlet opening to permit complete
point. Allow the engine to run at least two hours
at 180°F. so that cleaning solution may take
7. Turn on compressed air to blow out water and
effect. Do not drive vehicle or allow liquid level
loose sediment. Continue filling with water and
in radiator to drop low enough to interfere with
blowing out with air until flushing stream comes
5. Stop engine as often as necessary to prevent
8. For badly clogged engine water jackets that do
not respond to regular pressure flushing, remove
6. With the engine stopped, feel the radiator core
engine cylinder head and core hole plugs and
with bare hands to check for cold spots, and
with a suitable length of small copper tubing
then observe temperature gauge reading.
attached to the flushing gun nozzle, flush the
Where there is no change in temperature for
water jackets through openings.
some time, drain the cleaning solution.