The line runs to the other bellow boot on the other side, its there to allow air to move back and forth while remaining sealed from the atmosphere. When it compresses and depresses as you turn the air has to go somewhere so they just connect the 2 sides and they basically counteract eachother. And also the boot on the caliper piston, as long as you drive often it shouldnt be an issue especially on the front, id maybe throw some silicone hi-temp brake grease (just not petrolleum) around it and kind of inside to repell water, most fail from old contaminated fluid so i wouldnt lose any sleep over it.
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The line runs to the other bellow boot on the other side, its there to allow air to move back and forth while remaining sealed from the atmosphere. When it compresses and depresses as you turn the air has to go somewhere so they just connect the 2 sides and they basically counteract eachother. And also the boot on the caliper piston, as long as you drive often it shouldnt be an issue especially on the front, id maybe throw some silicone hi-temp brake grease (just not petrolleum) around it and kind of inside to repell water, most fail from old contaminated fluid so i wouldnt lose any sleep over it.