I have an E34 525td which had the same problem. After much investigation we found that if you turn the wheels slightly to one side then go to the front of the car and kick the front wheel right on the flat of the tyre (forcing the wheel back towards the cockpit you should hear a rattle. If this is the case it is more than likely your control and thrust arms. These are readily available from eurocarparts. The arms are very easy to fit but you'll need a ball joint separator. The number for eurocarparts is (UK) 0541 506 506. If you need anymore advice on how to change them e-mail me on pfobbester@hotmail.com.