I would advise against rad weld and trace the leak! You could always as some ultraviolet dye to the water and leave it in there of a month and then scan the engine bay with ultraviolet lamp & glasses. Then you will find the leak. Dont forget with a Renault to always use coolant added to the sytem. With these fixes in the bottle you always run the risk of blocking up somewhere you don't want! You have been warned!

Most independant garages that service Air con will have the dye in bottles, you only need a tiny amount and they have the lamps etc. We use to charge about 3/4 hr labour for the job all in. Suprising usually where the water leaks turnup !