Thanks CSA for taking the time to reply. I now understand what you’re saying, and it sounds reasonable that an “open” system is subject to evaporation.
You’re Welcome Joe.
How it about it techs? Is this the difference between coventional flow and reverse flow cooling?
I will add a detail about the cooling system atypical of Natural Aspirated ones. I have a top coolant reservoir with its own radiator cap. Basically this item allows for coolant that vaporizes on a shut down turbo/engine to continue flowing and drawing coolant around the turbo until the system equalizes(cools turbo enough). I have a feeling vaporizing coolant is atypical of normal cooling systems.
Perfect explanation. That’s what I was trying to get at with my post, but I couldn’t put it nearly as clearly as you did. The non-turbo Outbacks have an “open” system…the gap around the return hose is easily large enough to allow for 1-2 cups loss via evaporation over a 30K mile period. In fact, my first post on Car Talk was about my “mysterious coolant leak,” which has proven to not be a leak at all. All of my prior cars have had “closed” systems with pressurized reservoirs, so I wasn’t used to losing any amount of coolant, but after having the Outback in the shop twice for pressure testing etc., and checking some other Subaru forums, I’ve come to the conclusion that losing a cup or two of coolant each year is completely normal for an “open” system like mine.
I don’t know about the certainty of saying there should be no loss of coolant or if there is it’s due to a PROBLEM leak.
I always thought there was a some loss of coolant, from evaporation or some such, if you had a plastic overflow reservoir bottle, just due to the nature of the beast so to speak.