Chevrolet 10 Series 1967, Service Manual

Page: 321 / 605

SECTION 6K
ENGINE COOLING
IN D EX
Page
General D e s c r ip t io n ......................................................... ... 6K-1
Maintenance and A d ju stm en ts.......................................... ... 6K-1
Coolant L e v e l .................................................................. ... 6K-1
Coolant System Checks................................................... ... 6K-1
Periodic Maintenance...................................................... ... 6K-2
C leaning........................................................................ ... 6K-2
Reverse Flushing......................................................... ... 6K-2
R ad ia to r..................................................................... ... 6K-2
Page
Cylinder Block and Cylinder H e a d ........................ 6K-2
Hot Water H eater................................................... 6K-2
Fan B e l t .................. ........................................................ 6K-2
A d ju s tm e n t.................................................................. 6K-2
T h e rm o sta t..................................................................... 6K-2
Replacement.................................................................. 6K-2
Water Pum p..................................................................... 6K-3
R em oval........................................................................ 6K-3
In s ta lla tio n .................................................................. 6K-3
GENERAL DESCRIPTION
A pressure cooling system is provided for on all
models by a pressure type radiator cap (fig. 1). The
pressure type radiator cap used is designed to hold a
pressure above atmospheric pressure in the cooling
system. Excessive pressure is relieved by a valve within
the cap that opens to radiator overflow.
The water pump is a ball bearing, centrifugal vane
impeller type. It requires no care other than to make
certain the air vent at the top of the housing and the drain
holes in the bottom do not become plugged with dirt or
grease. Removal and installation of the water pump is
covered in this section. For overhaul procedures of the
water pump refer to Section
6
K of the Passenger Chassis
Overhaul Manual.
For radiator, refer to Section 13 of this manual. For
radiator shroud, refer to Section 11 of this manual.
Fig. 1—Pressure Radiator Cap
MAINTENANCE AND ADJUSTMENTS
Coolant Level
The radiator coolant level should only be checked when
the engine is cool, particularly on cars equipped with air
conditioning. If the radiator cap is removed from a hot
cooling system, serious personal injury may result.
The cooling system fluid level should be maintained
one inch below the bottom of the filler neck of the radia­
tor when cooling system is cold, or at the bottom of the
filler neck when the system is warm. It is very impor­
tant that the correct fluid level be maintained. The seal­
ing ability of the radiator cap is affected when the cooling
level is too high.
All passenger car cooling systems are pressurized
with a pressure cap which permits safe engine operation
at cooling temperatures of up to 247°F.
When the radiator cap is removed or loosened, the
system pressure drops to atmospheric, and the heat
which had caused water temperature to be higher than
212°F, will be dissipated by conversion of water to
steam. Inasmuch as the steam may form in the engine
water passages, it will blow coolant out of the radiator
upper hose and top tank, necessitating coolant replace­
ment. Engine operating temperatures higher than the
normal boiling point of water are in no way objectionable
so long as the coolant level is satisfactory when the
engine is cool.
Upon repeated coolant loss, the pressure radiator cap
and seat should be checked for sealing ability. Also, the
cooling system should be checked for loose hose con­
nections, defective hoses, gasket leaks, etc.
Coolant System Checks
1. Test for restriction in the radiator, by warming the
engine up and then turning the engine off and feeling
the radiator. The radiator should be hot at the top
and warm at the bottom, with an even temperature
rise from bottom to top. Cold spots in the radiator
indicate clogged sections.
2. Water pump operation may be checked by running the
engine while squeezing the upper radiator hose. A
pressure surge should be felt. Check for' a plugged
vent-hole in pump.
NOTE: A defective head gasket may allow ex­
haust gases to leak into the cooling system.
This is particularly damaging to the cooling
system as the gases combine with the water to
form acids which are particularly harmful to
the radiator and engine.
3. To check for exhaust leaks into the cooling system,
drain the system until the water level stands just
above the top of the cylinder head, then disconnect
the upper radiator hose and remove the thermostat
and fan belt. Start the engine and quickly accelerate
several times. At the same time note any appreci­
able water rise or the appearance of bubbles which
CHEVROLET TRUCK SERVICE MANUAL