That is a vacuum can or reservoir.
The actual vacuum system is unknown. However, the picture looks like it is from a vehicle from the 70s and a full sized Ford or Mercury with a Windsor block engine.
Anyway, the possible vacuum systems are: (in no particular order)
HVAC
Power door locks
Speed control
Concealed head lamps - however that reservoir may be larger
Or some other vacuum controlled circuit
The purpose is to maintain a vacuum signal during periods when engine vacuum is low. Like dropping the pedal on the right to the floor. This would cause engine vacuum to drop to near zero.
Action
The actual vacuum system is unknown. However, the picture looks like it is from a vehicle from the 70s and a full sized Ford or Mercury with a Windsor block engine.
Anyway, the possible vacuum systems are: (in no particular order)
HVAC
Power door locks
Speed control
Concealed head lamps - however that reservoir may be larger
Or some other vacuum controlled circuit
The purpose is to maintain a vacuum signal during periods when engine vacuum is low. Like dropping the pedal on the right to the floor. This would cause engine vacuum to drop to near zero.
Action
