WHAT'S SO BAD ABOUT '57 & '58 BUICK VACUUM WIPERS? in Buick - Post War Posted June 8, 2011 · Edited June 8, 2011 by stealthbob (see edit history) That auxiliary vac pump on the 54's was for the power brakes during an engine stall at speed. No Vacuum=No Brakes! They only ran when the ignition was on but the engine was not so I doubt full time duty would be ideal as that would wear them out quick. Also they are a little dear as it pertains to costThere were two models, Trico and Morvac.