1998 Mercury Mountaineer 175,600. Temp gage needle is fluctuating between "H" red line and "C "
No coolent pressure in radiator hose. Radiator was empty put in gallon of 50/50 coolent mix. Drove four miles engine started steaming and pouring out of tail pipe. Got home let engine cool. Next day put water in radiator and it almost all leaked out of bottom of radiator. Next day drove car half a mile to mechanic. Keep in mind this is a used radiator from a junk yard I had installed back on 08/10. Possibly leak in radiator? Could it be a stuck thermostat? Or bad water pump?
There are more serious problems if coolant is coming out of the tail pipe. That would indicate a leaking head gasket which is rather serious, but that isn't very common on that engine.
Combustion gases can also get pushed into the cooling system through a leaking head gasket, but system pressure shouldn't go over 15 psi if the radiator cap is releasing properly. A 12-year-old radiator really shouldn't be corroded though yet, especially two of them. If one of the radiator tanks is split open or cracked, you might want to replace the radiator cap. Regardless, there shouldn't be any coolant running out of the tail pipe.