I was driving my dad's 02 superduty the other day and noticed a deep whining sound coming from under the hood when slowing down and when turning. It also makes the sound when I am stopped and I put my foot on the brake. I can feel the brake pedal vibrate a bit as it is making the whining noise. It sounds a lot like the power steering on our 94 f150. I would think it has something to do with the power steering but I don't know why it would make the noise when I hit the brake. Anyone know what the problem might be?

 

Due to no vacuum on a diesel motor, the power brakes are powered by the poewer steering pump along with the steering. The two systems are linked, so that is why you hear the whine with both steering and brakes. Try topping off the fluid to spec and maybe doing so with a good additive for p/s systems. Should help deaden the whine.

In the longer term, you may need to replace your booster. Hydrobooster.

 

read this thread. flushing the fluid out was a great improvement.

https://www.ford-trucks.com/forums/4...Power+steering