Chevrolet 70 1969 Series, Shop Manual

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ENG INE C O O L IN G SYSTEM 6K-2
liquid to flow through cooling system, until engine
reaches normal operating temperature.
During engine warm-up, coolant is recircu­
lated back through by-pass at side of water mani­
fold and into engine to assist in warm-up of engine.
As engine water temperature reaches normal,
thermostat valves become fully open. The valves
then may move frequently to regulate flow of cool­
ant into radiator. Thus an efficient operating tem­
perature is maintained. A temperature gauge on
dash is connected to a thermal unit in engine cyl­
inder head water outlet manifold.
6V-53 D IE S E L E N G IN E (Fig. 2)
Coolant is drawn from lower portion of the
radiator by a belt-driven water pump and discharg­
ed through engine oil cooler passages to cylinder
block. From cylinder block, coolant flows up through
cylinder heads and forward to thermostat housing
at front of each cylinder head. If engine is at oper­
ating temperature, coolant flows through thermo­
stat housing to upper portion of radiator. If engine
is below operating temperature, coolant is return­
ed to suction side of water pump through a by-pass
system. Two thermostats control engine operating
temperature by regulating the volume of coolant
flow through the radiator core.
Engine Warm-up Period
During the engine warm-up period, thermo­
stats direct coolant back to suction side of water
pump. Coolant is recirculated within the engine to
shorten engine warm-up period. As engine reaches
OVERHEAT ALARM
THERMOSTAT HOUSING
BY-PASS TUBE
/
J m
H I
THERMOSTAT
HOUSING
TEMPERATURE GAUGE
SENDING UNIT
l/ ■
,
\
Figure 2 — Coolant Circulation (6V-53 Engine)
CHEVROLET SERIES 70 -80 H E A V Y DUTY TRUCK SH O P M A N U A L