Roaring noise when turning on 1996 Volvo 960

My mother's 1996 volvo 960 sedan makes a roaring noise when you make a turn while driving it. What could be causing this, the power steering maybe? It is not running hot, but the check engine light stays on all the time. The tires seem ok and are not worn. It has 120k on it, does not use any oil, but does seem somewhat sluggish lately. The radiator does have a slow leak as I have to add water to the overfill tank every couple of weeks. It is only driven once a week on short trips. I would appreciate any information, Thanks.

Asked by for the 1996 Volvo 960
Definitely check the power steering fluid, it may be low. You may also have a bad wheel bearing, but it's hard to say without actually hearing the noise first hand.
This model had some issues with a vibrations from the power steering system, and an upgrade of the power steering hoses may need to be performed if you are getting a vibration when turning the wheel.
Have the diagnostic codes checked, these are stored when the check engine light comes on, if you post the codes here I can give you a good idea as to what is likely needed.
Get the radiator replaced, if the engine were to overheat, the engine can be damaged severely, costing thousands of $$ to repair.