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CS
RADIATOR DRAINCOCK (Continued)
Fig. 13 Draincock
1 - DRAINCOCK ASSEMBLY
INSTALLATION
(1) Inspect the draincock body and O-ring for dam-
age. Replace as necessary.
(2) Position the draincock assembly horizontally to
the tank opening with the manufactures identifica-
tion mark facing down.
(3) Push the draincock assembly into the tank
opening while rotating clockwise until it snaps into
place.
(4) Close the draincock stem by turning clockwise
until it stops at the horizontal position.
(5) Fill the cooling system (Refer to 7 - COOLING
- STANDARD PROCEDURE).
PRESSURE CAP
DESCRIPTION
The cooling system pressure cap is located on the
collant pressure container. The cap construction
includes; stainless steel swivel top, rubber seals, and
retainer, main spring, and a spring loaded valve (Fig.
14).
OPERATION
The cooling system is equipped with a pressure cap
that releases excessive pressure; maintaining a range
of 97-124 kPa (14-18 psi).
The cooling system will operate at higher than
atmospheric pressure. The higher pressure raises the
coolant boiling point thus, allowing increased radia-
tor cooling capacity.
There is also a vent valve in the center of the cap.
This valve also opens when coolant is cooling and
contracting, allowing the coolant to return to cooling
system from coolant reserve system tank by vacuum
through a connecting hose. If valve is stuck shut,
Fig. 14 Cooling System Pressure Cap Filler Neck
1 - OVERFLOW NIPPLE
2 - MAIN SPRING
3 - GASKET RETAINER
4 - STAINLESS-STEEL SWIVEL TOP
5 - RUBBER SEALS
6 - VENT VALVE
7 - COOLANT PRESSURE CONTAINER
8 - FILLER NECK
or the coolant recovery hose is pinched, the
radiator hoses will be collapsed on cool down.
Clean the vent valve (Fig. 14) and inspect cool-
ant recovery hose routing, to ensure proper
sealing when boiling point is reached.
The gasket in the cap seals the filler neck, so that
vacuum can be maintained, allowing coolant to be
drawn back into the radiator from the reserve tank.
If the gasket is dirty or damaged, a vacuum
may not be achieved, resulting is loss of coolant
and eventual overheating due to low coolant
level in radiator and engine.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - COOLING SYSTEM
PRESSURE CAP TESTING
Dip the pressure cap in water. Clean any deposits
off the vent valve or its seat and apply cap to end of
the Pressure Cap Test Adaptor that is included with
the Cooling System Tester 7700 (Fig. 15). Working
the plunger, bring the pressure to 104 kPa (15 psi) on
the gauge. If the pressure cap fails to hold pressure
of at least 97 kPa (14 psi), replace the pressure cap.
CAUTION: The Cooling System Tester Tool is very
sensitive to small air leaks that will not cause cool-
ing system problems. A pressure cap that does not
have a history of coolant loss should not be
replaced just because it leaks slowly when tested
with this tool. Add water to the tool. Turn tool
upside down and recheck pressure cap to confirm
that cap is bad.
ENGINE 7 - 23
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