Komatsu WB140-2N Operation & Maintenance Manual page 178

MAINTENANCE
9. After draining the water from expansion tank (4), flush the tank's
inside and fill it with coolant until a level between the MIN. and
MAX. marks is reached.
10. Close the engine hood.
The cooling system must be flushed more frequently if the water
used contains a high quantity of calcium salts (if the water is very
hard).
3-60 WB140-2N, WB150-2N