2003 Mercury Mountaineer overheating

[landmagget]

4.0 eng. losing coolant out of coolant tank. I have performed everything on the cooling system. As it heats up coolant overflows out of the recovery tank before the thermostat opens. After thermostat opens it pulls coolant from tank. I have lowered the coolant in tank when engine is cooled down but it doesn't help. Also pressure checked for blown head gasket but that checks out ok. Any answers to this problem would be greatly appreciated.
Thanks

[shorod]

When they pressure tested the system did they pressure test the radiator cap to make sure it is able to let the system properly pressurize? If the cap is weak it could allow coolant to flow in to the tank rather than forcing the system to built pressure and therefore further increase the boiling point.

-Rod

[landmagget]

Thermostat has been replace twice. Radiator cap also was replaced. Made sure it had the correct amount of coolant in system

[shorod]

I wonder if the thermostat is backwards and therefore you need to get a lot of heat on the wrong side of the thermostat before it finally opens. I'm not sure if the housing will even support installing the thermostat backwards or not. Did you or anyone else recently have the thermostat out shortly before you started having this issue? If not, maybe the thermostat is just not opening as soon as it should and needs to be replaced.

-Rod

[landmagget]

Having this problem before anything was done. Maybe I need to go to the ford dealership and purchase the thermostat. That's all I know to do. I been in the auto repair for GM for over 25 years before I open my shop of 20 years. I know a little about mechanics but this has me at a stand still.

Thanks