Chevrolet 10 Series 1970 Service Manual page 361

General D e s c r ip t io n .............................................................6K-1
Maintenance and A d ju s tm e n ts .............................................6K-1
Coolant L evel ................................................................... 6K-1
Coolant System Checks ................................................... 6K-2
Periodic M a in te n a n c e ...................................................... 6K-2
Cleaning ...................................................................... 6K-2
R everse F lu s h in g ..........................................................6K-2
R a d ia t o r ...................................................................... 6K-2
A ll C h evrolet trucks have p ressu re type engine cooling
system s with therm ostatic control of coolant circulation.
The cooling system is sealed by a p ressu re type radiator
f ille r cap.
The pressu re type radiator fille r cap (fig. 1) is de­
signed to operate the cooling system at higher than at­
m ospheric pressu re. The higher pressu re ra ises the
boiling point o f the coolant which increases the e fficien cy
of the radiator.
The radiator f ille r cap contains a pressu re
va lve and a vacuum r e lie f valve.
va lve is held against its
com pressed, allows e x cessive p ressu re to be re lie v e d
out the radiator overflo w .
The vacuum valve is also held against its seat by a
spring which when com pressed, opens the valve re lie v in g
the vacuum created when the system cools off.
The cooling sys te m 's w ater pump is of the centrifugal
vane im p e lle r type. The bearings are perm anently lu­
b ricated during manufacture and a re sealed to prevent the
loss o f lubricant o r the entry of d irt and w ater. The pump
Coolant Level
The radiator coolant le v e l should only be checked
when the engine is cool, p a rticu la rly on trucks equipped
with a ir conditioning. If the radiator cap is rem oved
fro m a hot cooling system , serious personal injury may
result.
The cooling system fluid le v e l should be maintained
one inch below the bottom of the f ille r neck of the ra d ia­
to r when cooling system is cold.
flow radiators should be maintained three inches below
the bottom of the f ille r neck when the system is cold.
When a radiator supply tank is used the coolant le v e l
should be maintained one inch below the bottom of the
f i l l e r neck. It is v e r y im portant that the c o rre c t fluid
le v e l be maintained. The sealing a b ility of the radiator
cap is affected when the cooling le v e l is too high.
A ll truck cooling system s a re p re s s u rize d with a p re s ­
sure cap which p erm its safe engine operation at cooling
tem peratures of up to 247°F. as fo llo w s:
SECTION 6K
ENGINE COOLING
Page
GENERAL DESCRIPTION
r e lie f
The p ressu re r e lie f
seat by a spring which when
MAINTENANCE AND ADJUSTMENTS
Coolant le v e l in c ro s s -
IN D E X
Cylinder Block and Cylinder Head
Hot Water Heater C o r e .............................................6K-3
Fan B elt A d ju s tm e n t......................................................... 6K-3
Thermostat ...................................................................... 6K-3
R ep la ce m e n t................................................................... 6K-3
Water P u m p ...................................................................... 6K-3
R e m o v a l......................................................................... 6K-3
Installation...................................................................... 6K-3
F ig .
req u ires no care other than to make certain the a ir vent
at the top o f the housing and the drain holes in the bottom
do not becom e plugged with d irt o r grea se.
Rem oval and installation of the w ater pump is covered
in this section. Overhaul procedures of the water pump
assem blies are co vered in Section 6K of the Chassis
Overhaul Manual. F o r radiator s e rv ic e r e fe r to Section
13 of this manual. Radiator fan shroud replacem ent is
covered in Section 11 of this manual.
psi
9
13
15
When the radiator cap is
system pressu re drops to atm ospheric, and the heat
which had caused w ater tem perature to be higher than
212° F, w ill be dissipated by conversion of w ater to
steam . Inasmuch as the steam may fo rm in the engine
w ater passages, it w ill blow coolant out of the radiator
upper hose and top tank, necessitating coolant rep la ce­
ment. Engine operating tem peratures higher than the
norm al boiling point of w ater are in no way objectionable
so long as the coolant le v e l is sa tisfa ctory when the
engine is cool.
. . . ................ 6K-3
1— Pressure R adiator Cap
Max. Tem p.
235°
243*
2476
rem oved o r loosened, the
CHEVROLET TRUCK SERVICE MANUAL
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