Air Bleeding Of Cooling System; Gas Leakage Test; Coolant Leakage Test - Mitsubishi 6M70 Workshop Manual

4. Air Bleeding of Cooling System

• If the engine is started with the coolant filled up to the neck of the surge tank, the coolant temperature rises and
the expanded coolant overflows from the neck little by little. To avoid this, fill the surge tank with a slightly smaller
quantity of the coolant.
• With the pressure cap removed and the coolant temperature at 90°C, let the engine idle in order to bleed air com-
pletely out of the cooling system.
• After air bleeding is completed, refill the reservoir tank with coolant as needed.

5. Gas Leakage Test

6. Coolant Leakage Test

• Ensure that there is no coolant leakage from coolant system during idling.
• If any leakage is found, check for the mounting condition. If there is looseness, tighten the part to the specified
torque. If there are cracks or damages, replace the defective part with a new one. (See later section.)
• Presence of air or exhaust gas in coolant accelerates corrosion
of the cooling system components. To prevent this, carry out air/
gas leakage tests in accordance with the following procedure.
• Remove the pressure cap.
WARNING
• If the engine is hot, boiling coolant may spurt out from the
filler port when the pressure cap is loosened. To avoid
burning yourself, make sure to remove the pressure cap
only when the coolant is cold.
• Run the engine until the coolant temperature rises to approxi-
mately 90°C.
• If air bubbles appear continuously through the filler port, there is
air or exhaust gas penetrating into the cooling system.
• Presence of air in coolant can be an indication of loose cylinder
head bolts, loose water pump mounting bolts, loose hose con-
nections, and/or a damaged hose.
• Presence of exhaust gas in coolant can be an indication of a
damaged cylinder head gasket and/or cracks in the cylinder
head.
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