mc8 air pressure regulator for level control

[mc8 tin tent]

  Any one with info on what appears to be a air pressure regulator or prv control that is in the supply line to the rear level control valve?
I have a small leak coming from what looks like a bleed hole for maybe a diaphragm vent.
QUESTION can this be rebuilt or or is it a replacement only?
Thank you
Dwayne