Cooling System - Testing For Air Or
Combustion Gases (1-10)
Overflow Method
Warning: Wait until the temperature is below 50°C
[120°F] before removing the coolant system pressure
cap. Failure to do so can cause personal injury from
heated coolant spray.
Allow the engine to cool, and remove the radiator cap.
Install a radiator pressure cap which has had the spring
and the pressure relief valve removed to allow free flow
from the overflow tube.
Attach a rubber hose to the radiator overflow connection.
Put the free end of the hose below the water level in a
container of water.
NOTE: The pressure cap must be tightly sealed in the top
of the radiator fill neck.
Operate the engine at rated RPM until it reaches a tem-
perature of 82°C [180°F].
Check for a continuous flow of air bubbles from the hose
in the water container.
NOTE: The engine coolant temperature must be stable to
perform this test. An increasing coolant temperature will
give a false indication of air due to expansion of the coolant
in the system.
Sightglass Method
NOTE: The cooling system diagnostic kit, Part No. 3822994,
contains a sightglass and can be used to detect air or com-
bustion gases in the cooling system. Refer to the instruc-
tions supplied with the tool for installation instructions.
Section 1 - Cooling System Cooling System - Testing For Air Or Combustion Gases (1-10)
N14 Page 1-25
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