Radiator valves can typically be replaced without needing to replace the entire radiator. Radiator valves are often connected to the radiator via threaded fittings, making them relatively easy to remove and replace. It's recommended to turn off the heating system, let it cool, and drain any water from the radiator before replacing the valve. If you're unsure or uncomfortable with the process, it's advisable to seek assistance from a professional plumber or heating engineer.   We have a detailed post to see if it is a job for you - 'How to replace a radiator valve'.