Hi i have a ford fiesta and the heater is blowing hot then cold,?

rad weld don't bother & test temp sender unit take out of car & place saucepan boil kettle & pour boiling water onto temp unit don't stand right on because if has been stuck & opens boiling water can splash onto if thing opens nothing wrong temp sender unit whilst out may place hose pipe onto radiator & flush water through clear out air pockets, once have clean water coming out need replace the anti freeze (i expecting have anti-freeze in) otherwise can problem. before fill radiator top 1 hens egg & make sure water cold open egg top of radiator yes 1 plain egg, take car on small 5 10 mile run find there may little water replace & while remember put egg in before can see top of inside tubes in radiator should have sorted thing & may need hens egg every 3-months works raced 1600 race engine radiator had hole big enough put fist in & took half dozen eggs drop radiator & guess won race & yes water lot lower proved point. best wishes.

i have top coolant there small leak, head gasket isnt blown, temp guage stays normal, has got suggestions, faulty themostat, , advisable use radweld leak, thanks

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