Check coolant level on side of de-aeration tank. Level should be at or above Min Cold line (C). If level is low, before adding coolant check for any signs of leakage. Repair if necessary.
IMPORTANT: Do not open de-aeration tank cap (B) when engine is warm. Doing so will add air to coolant system.
NOTE: If coolant level is low, but there is no sign of an external leak, there may be an internal coolant leak. Contact your John Deere dealer.