One problem related to steering rack and pinion has been reported for the 2003 BMW Z4. The most recently reported issues are listed below.
2003 BMW Z4 roadster has an intermittent sticky steering issue that adversely affects the ability to control the direction of vehicle in traffic. The condition is due to high ambient temperatures or after parking car in hot weather. The steering wheel will not allow the driver to steer a straight line without constant, sudden corrections that require use of the entire lane of traffic. A bicyclist was almost struck by vehicle which prompted this complaint. The failure happens every time the car is driven in weather above 75 degrees f and parked in sun. The condition will dissipate when car is parked in shade or temperatures fall for a prolonged period. BMW dealer servicewriter was contacted and knew nothing about other Z4 vehicles with electric steering having this issue. Dealer advises replacing the entire steering upper column assembly and the lower rack and pinion with an estimate of $4943. 00. Owner is exploring options for repair or replacing vehicle with a newer model.