Brakes making weird sound inside

[Zogman]

My coach is an 02 8311 on a Ford chassis. I've had it a month and I'm learning more by the day. So here goes...

While the engine is running, if I depress the brake pedal, I hear a whistle sound coming from under the dash. The brakes work perfectly but it sounds like I have air-brakes. I got under there and pushed the brake and I guess it sounds like air is coming from the booster but if I remember right, these are not vacuum assisted brakes, they are fluid assisted from the power steering... I think. So what the heck is going on here? Thanks
Zoli

[Zogman]

My coach is an 02 8311 on a Ford chassis. I've had it a month and I'm learning more by the day. So here goes...

While the engine is running, if I depress the brake pedal, I hear a whistle sound coming from under the dash. The brakes work perfectly but it sounds like I have air-brakes. I got under there and pushed the brake and I guess it sounds like air is coming from the booster but if I remember right, these are not vacuum assisted brakes, they are fluid assisted from the power steering... I think. So what the heck is going on here? Thanks
Zoli

[speed racer]

They are hyd. assist and what you hear is the pump loading and hyd. oil passing threw the lines.