Komatsu PC300LC-8 Operation & Maintenance Manual page 290

MAINTENANCE MAINTENANCE
12. Drain the coolant from sub-tank (5), clean the inside of the
sub-tank, then add water until the coolant level is between the
FULL and LOW marks.
If the sub-tank is extremely dirty and it is difficult to clean,
replace it with a new part.
13. Stop the engine, wait for approx. 3 minutes, add Supercoolant
up to the bottom of the filler port, then tighten the radiator cap
(2).
MAINTENANCE PROCEDURE MAINTENANCE PROCEDURE
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