The problem relative to the Vacuum boost pump on the twin turbo echoboost 2011,2012 Ford F150 is well know failure. From experience, the vacuum boost pump will start making noise when it is getting ready to fail... So if you hear a loud humming, or grinding noise near the drivers side headlight the pump is about to fail. I have had two such failures, the first was a total failure, the second was the loud noise and I got it in before total failure.
From experience, if the vacuum boost pump totally fails the vehicle will have unpredictable braking... At times almost normal and others almost no breaking... Once the pump fails you will get a visual and audible warning that the brake system has a major fault.
Our truck is a platinum which I think has some extra sound proofing so all I could hear inside the truck was a distant buss or low frequency humming noise.. Outside the truck the noise was loud and consistent with metal to metal grinding noise till it totally fails.
Access to the pump is easy... Its under the drivers side headlight. If under warrantee which both of ours were then other than inconvenience its a short visit to the dealer. If not under warrantee and one wants to do the repair themselves then the pumps are available from various sources... I have not done the repair but the replacement does not appear to be complicated...
