Its a Volvo Problem

[Magard]

Probably not brake chambers. Maybe in your parking valve. If it’s bypassing air out of that vent. Sounds like that might be where I would start. Brake chambers leak out of themselves when they go bad. I’m trying to remember what symptoms I had once when I had to replace one of those park valves in the dash. Can’t remember if it was leaking but it quite working for some reason.