I have an oil fired boiler with forced hot water
Cast iron radiators with a dual pipe system & diverter valves on main pipe
Each radiator has an ON/OFF valve on the radiator
Many do not work & are open all the time
Heat works just fine

I'm having two radiators moved, & the on/off valves doe not work
We never turn them off or on
Shining a flashlight down the pipe/valve I can't even see any way that it closes to stop water

Should I have the valves replaced ?