where is the vacuum reservoir located?

Look for a sphere shape..a ball.. with vacuum lines..on some of those Fords it's attached to the hood and people miss it, looking all over engine compartment and it up high with hood open

or have a look at this

The vacuum Reservoir is located in your AC condenser / heater core compartment. This is an extraordinary large task to undertake to get to the vacuum Reservoir however I just repaired an E350 2010 Ford vacuum system. Dorman makes a vacuum ball and a check valve for everyday use. All I did was run the vacuum line from the intake to the vacuum ball and I located it under the coolant reservoir on the driver side and ran the line coming off of the vacuum Reservoir ball inside the cab through the electrical wiring harness Boot and over to the black line on the AC vacuum system that gets its vacuum from the existing vacuum Reservoir it works great and looks great and you won't have to deal with the old vacuum Reservoir anymore it's basically just taking the old Reservoir out of the loop hopefully this helps it is about a 45 minute fix cost you about $35 for the vacuum line vacuum ball and check valve