· Super Moderator
First off, just to use the correct words, vacuum is the absence of pressure. The vacuum "reservoir" is just that. It holds vacuum so that when you throttle up and the manifold vacuum drops, you still have vacuum to operate the things that need vacuum, like the HVAC air distribution doors. If you have a leak, everytime you get into the throttle, the HVAC will default to defrost mode (lack of vacuum). Also the system will bleed down when you shut down the engine and the parking brake will not release. Sounds like you have a leak somewhere. I would replace that reservoir and check all the vacuum lines.