I have the same car, same problem. Well, actualy 1990 with about 160,000 miles. I know it sounds rediculous, it seems like the P/S fluid vanishes, it doesn't show any signs of leeking . . . trust me I've been looking. We add P/S fluid every week almost, more when it's cold out believe it or not. When it is cold out, if the P/S fluid is not kept to the max, that groaning and whirring you mentioned was very bad in my car. Would happen every morning for about 5 minutes and was ok after it warmed up. The groaning durring turns would still happen although the whirring noise stopped. You can feel that the steering column is stiff as well. Since we seem to have been pooring money into the car, we're putting off getting the pump replaced. My best temporary fix to sugest for you is to add fluid, and keep it full. This does it for me.