Chevrolet Light Duty Truck 1973 Service Manual page 411

General Description........................................................ 6K-1
Theory of Operation....................................................... 6K-2
Maintenance and Adjustments.................................... 6K-7
Coolant Level................................................................... 6K-7
Coolant System Checks................................................ 6K-7
Periodic Maintenance................................................... 6K-8
Cleaning.......................................................................... 6K-8
Reverse Flushing.......................................................... 6K-8
Radiator........................................................................ 6K-8
Cylinder Block and Cylinder H ead.................... 6K-8
Fig. 1—Radiator Pressure Cap
All trucks have pressure type engine cooling sys­
tems with thermostatic control of coolant circulation.
The cooling system is sealed by a pressure type radiator
filler cap.
The pressure type radiator filler cap (fig. 1) is designed to
operate the cooling system at higher than atmospheric
pressure. The higher pressure raises the boiling point of
the coolant which increases the efficiency of the radiator.
The radiator filler cap contains a pressure relief valve
and a vacuum relief valve. The pressure relief valve is
held against its seat by a spring which when compressed,
allows excessive pressure to be relieved out the radiator
overflow.
The vacuum valve is also held against its seat by a spring
which when compressed, opens the valve relieving the
vacuum created when the system cools.
The cooling system's water pump is of the centrifugal
vane impeller type (figs. 2 and 3). The bearings are
permanently lubricated during manufacture and are
sealed to prevent the loss of lubricant or the entry of dirt
and water. The pump requires no care other than to
make certain the air vent at the top of the housing and
SECTION 6K
ENGINE COOLING
INDEX
Fan Belt Adjustment..................................................... 6K-9
Radiator C ap ................................................................... 6K-9
Thermostat........................................................................ 6K-9
Thermostatic Fan Clutch Replacement.................. 6K-9
Water Pum p..................................................................... 6K-10
Diagnosis.............................................................................. 6K-11
GENERAL DESCRIPTION
the drain holes in the bottom do not become plugged
with dirt or grease.
Water pump components are not serviced separately;
therefore, in the event of water pump failure, it will be
necessary to replace the complete assembly — removal
and installation procedures are covered in this section.
For radiator service refer to Section 13 of this manual.
Radiator fan shroud replacement is covered in Section
11 of this manual.
E N G I N E C O O L I N G
Heater Core.................................................................. 6K-9
Replacement................................................................... 6K-9
Removal.......................................................................... 6K-10
Installation...................................................................... 6K-11
Fig. 2—Water Pump—Typical L-6
6K-1
LIGHT DUTY TRUCK SERVICE MANUAL