Cooling System - Air or Combustion Gas Test (008-019)
B3.9 and B5.9 Series Engines
Section 8 - Cooling System - Group 08
NOTE: The pressure cap must make a tight seal.
Install a radiator pressure cap that has had the spring and
pressure relief valve removed.
Attach a rubber hose to the radiator overflow connection.
Place the free end of the hose in a container of water.
Operate the engine at rated rpm until it reaches a tem-
perature of 80°C [176°F] with the thermostat open.
Check for a continuous flow of air bubbles from the hose
in the water container.
A continuous flow of air bubbles can be caused by one of
· Fan, shutter, or heater air control thermostat valve
· An air compressor cylinder head leak. Refer to Pro-
cedure 012-019 for air compressor leak test.
If one of the air control valves or the air compressor was not
the source of air entering the cooling system, perform the