I noticed that I am leaking coolant at the overflow tank cap (which is the green cap, if that matters). There seems to be a fair amount of pressure in the overflow tank; which is unlike any other car I've seen, as I've always assumed that the overflow tank is completely unpressurized. Is this normal?

The car does not overheat, although eventually after a week, the low-coolant light comes on and I put in a pint of coolant.

In the past few months, I've had both the radiator replaced (due to a leak), and the thermostat (not working, i.e. top rad hose was never rigid/full when hot).

Any ideas on what to do next? Two different service stations are clueless, so my next stop will be the dealership.

Thanks (in advance) for any help.
=stan=