Search text

Hello.
I’m trying to change the text on search from english to portuguese, but I can’t find how to do it (http://imgur.com/a/KvMYd).
My wordpress is already in Portuguese, but some little things like the search, didn’t changed at all.
In the searchform.php I managed to change it, but the search in the header it’s not that easy.
I want to change “To Search start to typing” to portuguese. Can you help?

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