99 E-Class=210 Chassis
89 E-Class=124 Chassis
These are two differnt cars entirely. Kind of like apples and oranges. The 210 has clock spring that makes the conctacts to the steering wheel. The 124 has carbon brushes that ride on a slip ring to make the contact. In the case of the 124 most likely you have a large amount of carbon dust built up in this area causing the noise. To repair remove the steering wheel and clean the dust out. It would also be a good time to replace the brushes. Be careful about using lubricant on electrical contacts.