There was a thread on here a while back that got many laughs. A guy was having the opposite problem as you. His car was making radiator fluid and he was having to syphon some out about every week. He couldn't figure out what was going on, then one day he found out that his wife was mistaking the mark on the resevoir tank and was adding fluid each time he took some out. This was going on for months...with both him and his wife not knowing what was happening. I remarked that as tidy as my wife is, I'm very happy that she doesn't know enough about cars to do any tinkering. It's bad enough that she cleans up my office so that I can't find anything that I need.

Now, on a serious note, I agree that the system needs to be pressure tested. Seems like a gasket leak to me too.
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Current owner of a '04 V70 2.5T. Previous owner of a '94 850 Turbo Wagon