Whining Escape

this winter our 2001 Escape started making an intermittant whining noise that seemed to vibrate the steering wheel. At first I thought it was the power steering but it increased with speed, not turning.

I suspected the speedometer cable and took it to my trusted mechanic. There is no speedo cable. He test drove it for a day but couldnt reproduce the sound. he found a broken stabalizer rod and worn tie rods which I had him repair.

Two weeks later the noise returned. I looked under the hood and saw the 3/4 inch hose elbow connected to the back of the rocker cover was callapsed and the whine was coming from the engine.

the car has 57000 miles and has had a mysterous oil leak for several years which I now suspect might be from this same hose area. It also gets from 13 to 18 mpg. I have asked the dealer and my mechanic about the leak and mileage several times in the past. they said they cant find anything wrong and the leaks are from the new rubber gaskets that shrink with age and are expensive to repair.

What is the hose and what would cause it to collapse? Will replacing it help the gas mileage and stop the whine?