Normal Coolant Consumption

[tucsonjwt]

I think coolant level should never go down in a properly sealed cooling system. Am I wrong? I seem to lose about 1 pint of coolant every 2 months. I cannot find any leaks. Could it be leaking internally and going out the exhaust pipe? I see no white smoke. Coolant reservoir was replaced several years ago and seems to be intact. I did have a leak in the front of the intake manifold at the gasket, but bars leak seems to have fixed that a couple years ago. Temperature gauge remains constant at about 160 degrees (I have a 160 degree thermostat) with only city driving. Coolant looks clean, nice and green, and no milky appearance or antifreeze in the oil. Radiator, water pump, fan clutch replaced last year. Any thoughts?