"上周五开车, 发现engine overheated. 停下检查, 发现塑料罐coolant 没了, 加满后停车状态下未见coolant滴下."
update:
Thanks to all your help! Just as Ban Zhu said, the thermostat should be replaced. Then coolant has to be filled again if the technician didn't follow SOP. THanks again!