Clunk when releasing brake pedal

[Didrik84]

Hi all iv got 2015 peugoet partner 1.6hdi and looking for a bit of mechanical advice if I may please.. since iv owned the van its always had this annoying clunk sound when I'm coming off the brake pedal it's almost like a metallic sound so far iv checked all the metal parts and possible bushes related to the pedal mechanism and can't find anything untoward so I'm a bit stumped as to why it's doing it...