Can anyone help me?

[Flame.b]

Hi I have a rover25 it had a water leak which fixed but since then the cars really struggled to keep it's temperature down it isn't over heating as it's not hitting the red zone but it's only just staying below it when I first set out the fan will start cool it down and the go off again but after about 20mind the fan will just stay on constant and I can smell coolant or something coming through the heating vents but garage says can't find a problem?