How do, again,
We've been having similar toils and trials too.
We put some k-seal in to it, and it seemed to solve it, car got warm, if not hot! gurgling carried on, then went on a 30 mile drive, stopped, fine, moved another 2 miles, and now we've had a bigger blow out.
Took it to the local indy, put a pressure tester on the expansion tank, and water poured and poured from the rad. Theres a hole in it somewhere at bottom, so i'm going for a new rad, and gasket for the hell of it.
The indy guy said the gurgling sound through the air vents is air in the system thats come in through the hole, as its only leaking when not under pressure (i.e. engine off).
It won't be done till next week, so will let you know how it goes on, gonna renew all the clips and inspect EVERY hose while i'm at it. Replacing if needed. Handy having an auto shop open 9-9 7 days a week!
also, brass radiator plugs are a marvel!!