we had the vacuum pump fail on our F350 diesel which basically give you no brakes as power boost is not there, fortunately the failure occurred on Long straight offramp which allowed the use of the trailer brakes to bring the rig (with horses) to a stop
Bad thing was we had just had a “complete” brake job done of the truck. Went back to the service center told them that a Complete Brake job on a diesel better include the vacuum pump in the future. That pump only cost $38 and took about five minutes to replace