You'd better hope to God it's not the "coolant recovery tank hose". Ford wanted to charge me $671 in labor alone to replace the hose. There is a plastic "T", to which the hoses are molded. The heater control valve is easy to visibly inspect and confirm (Google for pictures to get an idea). Check the recovery hose plastic tee by carefully wiggling it after the engine is warm. Wear gloves, or else... Also, the plastic coolant reservoirs get brittle and crack over time.

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2002 Ford Ranger 2.3L 4cyl