The Quad 4 has alot of head gasket problems. Have the system pressure tested, and or have a block test done to check for exhaust gasses in the cooling system..If the vehicle has overheated recently more likely than not it has a warped head..
Most commonly this is due to overheating or a blown head gasket. Overheating causes the coolant to expand, and rush into the resevoir, then overflow it. When cool, the coolant that remains will be sucked back into the engine. A blown head gasket can cause the coolant to enter the firing chambers of the engine then be blown out the tailpipe, or the compression can leak into the coolant area and push the coolant out, or allow the coolant to get into the oil pan.
Overheating can be a number of things. Bad water pump, coolant low, fan inop, bad thermostat, leaking coolant, cooling system clogged, or a blown heads gasket. Check for coolant around the water pump signaling a bad water pump. if the temperature rises and no fan comes on, that's your problem. blown head gasket- look for coolant in the oil or oil in the coolant. it will look like a milkshake. uncap the radiator while its COLD. start the car, look to see if it bubbles. all suggest a blown head gasket.