It is not uncommon for the radiator to develop a coolant leak. A leaking radiator will require replacement. When a leaking radiator is replaced the entire cooling system should be inspected and if any additional leaks are found they should be repaired also.
Car Problem Reports
BMW 323i Coolant Leak From Radiator
BMW 323i Problem
Average Mileage: 145,000 mi (80,000 mi - 210,000 mi)
Visitor, 1999 BMW 323i
Developed a Coolant Leak From Radiator. Had the whole cooling checked and replaced. Cost approx.$900.00.
Visitor, 1999 BMW 323i, 210,000 mi
Had my radiator replaced and hoses Dec. 2012. Everything seemed fine up until a couple of weeks ago when my radiator yellow light came on and I checked the coolant and it needed coolant. Now I notice a leak, some runoff on the ground after it was sitting a few hours. Should I have the hoses checked again and replaced, or it this some other problem.
Visitor, 2000 BMW 323i, 80,000 mi
I had this problem and had to have a cooling overhaul, see: engine overheating, water pump is a mandatory replacement if you don't want to fix it twice...