Postby smj999smj » Mon Mar 04, 2013 5:05 pm
When the engine gets hot, the coolant expands until it reaches the pressure limit of the cap and pushes coolant into the reservoir. As it cools, it contracts and creates a vacuum that pulls the coolant from the reservoir back into the engine. So, if the reservoir is overfilled, the coolant could get pushed out the reservoir vent and leave a puddle of coolant on the ground (as well as the parts of your engine compartment that it runs down). If you have rear heat and a large air pocket in the system, you could see some loss in coolant as the air is slowly purging out of the system. Another possibility is there is a leak in the system. If you have rear heat, you may want to check the coolant lines that run along the frame to the rear heater core as they have been known to develope leaks on some Pathfinders. Of course, check for leaks under the hood and at the front and rear evaporator case drains. As far as "purging," make sure the system is full, turn all of the heaters to the maximum heat setting and jack up the front of the vehicle as much as practically possible to let any air in the rear heater lines/core (if equipped) to move towards the front of the vehicle.