Komatsu GD555-5 Operation & Maintenance Manual page 139

OPERATION
CHECK BEFORE STARTING
Be sure to check the items listed here before starting the engine for the day's work.
CHECK COOLANT LEVEL, ADD WATER
Do not open the radiator cap unless necessary. Wait for the engine to cool down before checking the coolant in the sub-tank.
Immediately after the engine is stopped, the coolant is at a high temperature and the radiator is under high internal pressure.
If the cap is removed to check the coolant level in this condition, there is a hazard of burns. Wait for the temperature to go
down, then turn the cap slowly to release the pressure before removing it.
NOTICE
If the volume of coolant added is more than usual, check for possible water leakage.
Confirm that there is no oil in the coolant.
1. Confirm that the coolant in sub tank (1) is filled to a level
between FULL and LOW. If the level is lower, open the cover,
and fill coolant through the water filler of sub tank (1), to a level
between FULL and LOW.
2. After adding coolant, tighten the cap securely.
3. If the sub-tank becomes empty, there is probably coolant
leakage. After checking, repair any abnormality immediately. If
no abnormality is found, check the level of the water in the
radiator. If it is low, add coolant of the same density in radiator
according to the coolant density table in "CLEAN INSIDE OF
COOLING SYSTEM (PAGE 4-19)", then add coolant to the
sub-tank.
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WARNING
OPERATION