So i have had this problem for a while now. When it is cold and now even when its warm at times, my steering makes a strange humming sound. It happens when the steering wheel is stright. A humming noise is present, then when i turn the wheel it disapears. Any ideas? Maybe old fluid? Its a 91 740 turbo.

 

I'd drain and refill

 

I agree with the drain and refill. Use Volvo OEM power steering fluid, I used it and have had no issues, steering is emaculate...so far.

by the way, be VERY sure to bleed the system properly.

 

Make sure you don't have a leak in the system. If it is low because of leaking then flushing and filling will not take car of the problem. Also, is your alignment OK. If it is slightly off you may be turning the steering wheel slightly to keep it tracking straight. Not enough that you would notice it but enough to place the power steering pump under a load.

 

I took some of the old power steering fluid out of the reservoir today and it was a murky color and didn’t look good. I put about a half a quart of new fluid in, it was the basic advance auto parts fluid and I know I just contaminated it with the old but I didn’t want it to be low. My question is, how do I go about draining and refilling the power steering fluid properly. The online guide here isn’t too helpful… http://www.swedishbricks.net/700900FAQ/FAQSummary1.html Also im having a hard time finding Volvo approved power steering fluid. Any ideas? Thanks guys. It’s a 91 740 Turbo 4Door