There is a reservour for the steering and power brake booster.
It is a round metal cylinder with a metalcap with a center screw lock.
Fluid is Power steering fluid or ATF, which ever you have.
There is a filter in the bottom of the reservoir if it does not need service.
This filter can cause fluid starvation.
If still making noise after the service and or filter you need a pump change.
Not to bad.
Here is a link to the e24 site with lots of help.
http://normgrills.net/bcg/
Later,