roadtrippin

Type= 02 Impreza RS 2.5 (obvious) Problem was that I would lose 1/4 from overflow after each A/c use and it wouldnt return. Changed out radiator cap and I dont seem to be having the problem now. Hopefully that was it.

Simple: Run A/c or Defrost coolant disappears from overflow tank (no more than a 1/4 cup). Doesnt happen any other time. No symptoms of leaks, just loss from tank. Causes? History:New water pump, thermostat, rad, rad cap, hoses all done at subbie shop within last 10k. I almost want to think air in the system but Im not sure, because afaik when there is air in the system it usually runs hotter than normal, which in my case it isnt doing. The needle stays pegged right in the mid. Again there is NO visible leaks, no oil in coolant or coolant in oil....just a small loss from the overflow tank. Ideas....where to start?