Ford Repair: Engine Whining, dodge caravans, power steering fluid

Question
I have a 1999 Ford Ranger and there is a constant whining in the engine. It never stops and does not get louder or quieter as you accelerate or decrease speed. I was told this could possibly be from the power steering but I checked the fluid and it was full. Could this also be from air in the power steering fluid or can you provide me with another possible cause for the whining? Also if this is air in the power steering fluid then the instructions I've seen just say elevate the front wheels off the ground crank the truck and turn the wheels from side to side. Is there no valve or hose to disconnect or do you leave the cover off the resevoir or the cap from where you fill your power steering fluid at? Any help is greatly appreciated.

Answer
first lets try to determine where it is coming from

with your engine running does the noise change when turning the steering wheel

does it change when you turn on your headlights/wipers and blower motor

the first would indicate a power steering noise-if so is the fluid black-foamy-red

black would be dirty fluid and some resevoirs have very small screens in them that get dirty and restrict flow-i have seen this more so on toyotas and dodge caravans but if this is the case flushing the fluid may help-if it is red or clear it would be normal
foamy would indicate air in the system then we need to know how it got there. leaky seals can suck in air while not nec. leaking fluid

noise changes when electrical loads change may indicate alternator problems have alternator tested

a bad bearing in an idler or tensioner pulley will also whine and not nec. change during engine speeds a cheap stethescope from a parts house may help pinpoint the noise just be careful where you put it while looking for the noise.