There is an o ring inside the connection. There are two ways of one has two clips that have to beheld away from the clip catch ring to release the hose it will be hard to prise the hose out of the radiator try twisting the connection pipe gently clock and anti-clock wise with pipe pliers. The other type has one clip as above but the pipe twists into the radiator connection. Dont forget plenty of WD40 or similar release agent on the connection before / during and after on re-assembly
arizona kid
March 2012