steering is hard to turn when trying to park, but not all the time. it will go on 2001 Ford F-250 Super Duty

easy at first but if i need to correct it a little et is very difficult to turn

Asked by for the 2001 Ford F-250 Super Duty
1 answer
seem to get more difficult with brakes applied? if so, steering pump and/or hydroboost unit may be getting weak.