Same issue, 2017 Crossroad Plus, 3.6, AWD. Wondering if it’s time to go. Just began daily routine of hot on driver side, cold on passenger side. 90k miles. Unconfirmed estimates of $1,600.00 to replace heater core. Then belts and hoses. Hate to leave the car but it’s now getting to eat expensive parts & labor. Has anyone ever successfully flushed the core?