I have a small coolant leak and don't know where its coming from? I have replaced the radiator as i could see white deposits on the old one. I have also replaced the top radiator pipe and the t shaped pipe below the oil breather pipe. There doesn't seem to be any water in the oil and i'm sure there isn't any bubbling from the expansion tank with the pressure cap off.

Could it be core plugs? Does anyone know how to check this and where they are?