Originally Posted by GoneCamping
To me it sounds like hydraulic brakes with a Hydra boost system.... I had a Ford F800 wrecker that had that...would get the buzzing & whirring sound mostly when the control relay was faulty...
It is a hydraboost system, the poll is to find out which busses do have it ,and more importantly to me, which ones do not. A friend of mine told me that he had not seen one on any bus in his part of the world ( Montana) . I work on buses for our local school division for a living and have yet to see a hyd/diesel without it , but there seems to be an exception to every rule. The booster backup should kick in whenever there is inadequate pressure from the power steering pump... to ensure that you can always stop safely.
p.s. you forgot to enter your poll answer
I can assume you have the air/diesel / no whir, but I can't enter it for you