99 Cadillac STS Seville 174k miles.
Replaced radiator after HVAC issues ( http://www.cadillacforums.com/forums...y-getting.html ), and new surge tank, refilled using recommend coolant and method, it seemed to take roughly the same amount coolant to refill as I got out when draining, after topping up/rev the engine for an hour or so.
I now get the Check coolant level warning, and I let it cool down, and then top it up a little, about 1/4" below the recommended line on the surge tank, but after doing this , and when the engine gets warms it seems to be over flowing from the surge tank. The temperature gauge in the cat now regularly goes to the the first marker past halfway (say 1 o'clock), doesn't go past it, but it is cold outside at the moment, and my concern is that this will change when the 100F summers come, after a short period of driving, say 5 minutes, the temp gauge goes down again.
So, is this all part of the self-purging going on...and will takes several hundreds of miles to settle in? Previous to this (old rad) I've never had a single issue with the cooling system always been rock solid.