I just had an interesting experience with my sons 1989 740GL...about a month ago the power steering became rather stiff. Checked fluid and it was full. I thought the pump was beginning to fail and we were experiencing a cold snap (subzero). Not having time to work on it with him, I told him to live with it. Then a few weeks ago he couldn't start the car at school. Check alternator output and it was erratic...sometimes charging well and sonetimes not. Replaced the brushes which were worn and it continued to charge erratically. Then one day I had the hood up and noticed that the harmonic balancer seem to be slipping a bit. Long story short - replaced the harmonic balancer and that solved both the power steering problem and the alternator problem. Had I not noticed that slippage I probably would have dumped a bunch of money in parts that were not needed and I would still have the problems.