John 16:13

There are no masculine subjects in this verse other than ἐκεῖνος "that one." 

τὸ πνεῦμα "the spirit" is neuter.

τῆς ἀληθείας "the truth/true one" is feminine.

ἑαυτοῦ "himself/herself/itself" does not have a gender of its own. Its gender is determined by the gender of the noun it refers to or modifies.

So this text reads "it will guide" and "it will utter" and "what it hears" and "it will declare." Rendering the masculine pronoun "he" throughout this text is based on bias that "the spirit" is masculine, and disregards the fact that the noun is neuter.