Kubota — With recovery tank (2) :

A Kubota service procedure — check it applies to your exact model before use.

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Procedure

1. 2. If coolant level is too low, check the reason for decreasing
2. coolant.
3. (Case 1)
4. If coolant is decreasing by evaporation, replenish only fresh, soft
5. water.
6. (Case 2)
7. If coolant is decreasing by leak, replenish coolant of the same
8. manufacture and type in the specified mixture ratio (fresh, soft
9. water and L.L.C.). If the coolant brand cannot be identified, drain
10. out all of the remaining coolant and refill with a totally new brand

Source: manual:01-kubota-03e-series-wsm-manual-enu.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.