I have done a bunch of searching and found some good info, but I still need some opinions.

I have a 96 A4, 2.8 fw drive only. The power steering started whining a bit a month or so ago. I thought it was the pump at first because the fluid was not low, so I said ok I'll have to wait untill I can afford it.
Then a week ago the power steering started getting really hard and it started leaking out of the power steering reservoir cap(between the green cap and black dipstick insert). So I take the cap off and it bubbling real bad and is really low. I got some of the rediculously expensive audi oem fluid($25 a litre, RETARDED) and filled it up, then got the front end on Jack stands and bled it. Hmmmm? Noise went away and it started working again.
After that I start to get curious as to the cause and if it's gonna happen again. I figured I drive it to work and see what happens. It's about an 18 to 20 minute drive. I'm on the highway almost to work and it's working good with no noise. I get off the highway and it came back, just the whine, the power steering was still working. I get in the lot at work and pop the hood, the fluid is all frothy again but not leaking out of the cap since it isn't low and spitting up all over it(should the cap leak like that anyway?). So I say oh well have to deal with it later and proceed to work, yay.
I get out of work and am ready for the annoying whine the whole way home, but I start the car and...... Quite as ever even when I turn the wheels(I'm thinkin, WTF.) I take off and go home and once again, I get off the highway and it's back. Same thing today, it's quite when it's cold but starts whining either once it's warm or after it's been ran at a constant 2k rpm or so for 15 mins.
I'm thinking I'm sucking air in somewhere and this is why it's all frothy and bubbly. I'm going to try and replace the clamps on the suction hose and the cooler pipe. Any suggestions or other ideas would be awsome.

Also I was told the cap shouldn't leak like that and I've been told it should if there is pressure or what not. Any ideas there?

Last thing is, I think I'm going to drain the fluid and refill, but the Audi fluid is rediculously expensive. Where can I get some mineral fluid that will work for cheap, I have heard to use bilstein Mercedes fluid but I can't find any. It's supposedly $10 a litre.

Any suggestions or help would be greatly appreciated guys.

 

check your driver's side tie rod. if it's wet there, you're leaking from the rack. the pump is the large pulley under your coilpacks. i've blown 2 racks lol. i had the same whine when cold and goes away when warm. check out ecs, blauparts, and mjm for cheaper fluid. you should be using ch11s

 

The first thing I checked was the rack since it is a common problem, but it's dry and there is no fluid build up in the boots or anything. I don't think it's leaking, the fluid level doesn't go down. When it first happened it leaked out of the reservoir cap. The only thing I can think of is that it is sucking air in and overflowing basically.
The weird thing is that it only whines when the car warms up, when I start it and take off after it's been sitting it's quite.

Is there anywhere you can buy the chf 11 without ordering online, $18 or $19 plus $8/9 shipping isn't really cheaper.

 

check out the VW dealership. sometimes they are cheaper for the same exact part. i've had my pump and rack go but you may be experiencing a bad high pressure line. same thing happened to my dad's highlander. i thought he had a bad pump but the dealership said a bad line and replaced it under warranty. it's probably a very slow leak