Where is it leaking? At the radiator or at the block? Was the neck clean before you attached the hose? If it's leaking at the radiator neck, pay CLOSE attention to where it's leaking, you can easily have a cracked neck.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]