Steerin column

Steering columns support the steering wheel, guide the steering shaft and transmit steering torque to the intermediate shaft and steering box. Play, binding or an inadequately locked steering adjustment mechanism directly affect vehicle control. On MAN and Mercedes trucks, buses and vans, diagnosis must therefore distinguish between wear within the column, faults in the universal joints and movement in the cab mounting.

Steering columns are available in fixed, height-adjustable and tilt-adjustable versions, with mechanical or pneumatically operated locking mechanisms, depending on the specification. A telescopic steering shaft can accommodate changes in length; a crash-energy-absorbing design also has a separate safety function. These features are not interchangeable. Also check whether the supplied assembly includes the intermediate shaft, steering column switches, steering lock or steering angle sensor.

Always identify parts using the vehicle's chassis number. Visual comparison or selection by model name alone is never sufficient. Mountings and adjustment mechanisms may differ between MAN TGX with XL, XLX or XXL cabs and MAN TG3 TGX with GN, GM or GX cabs. The exact specification must also be checked for Mercedes Actros with Lang StreamSpace or Lang GigaSpace. Sprinter, TGE and Citaro, for example, also have vehicle-specific connections and installation dimensions.

Critical design parameters include installation length, telescopic travel, spline diameter and profile, the position of the pinch bolt grooves and the mounting geometry. Steel steering shafts, universal joints with needle roller bearings and plastic guide bushes each have different fit and lubrication requirements. Axial and radial play limits must be taken from the vehicle-specific workshop documentation; there is no universal rejection limit.

A knock when changing steering direction may indicate worn sliding splines, worn universal joints or loose mountings. Radial movement at the steering wheel can result from worn steering shaft ball bearings or guide bushes. Intermittently heavy steering is more likely to indicate binding universal joints or a steering shaft rubbing against adjacent components. A steering wheel that drops requires inspection of the adjustment clamp and, where fitted, the pneumatic release mechanism.

1. Park the vehicle safely with the wheels pointing straight ahead and secure it against rolling. Inspect mounting brackets, pinch bolts, dust boots and bulkhead passages for cracks, corrosion and signs of contact.
2. Have a second technician gently apply alternating left and right pressure to the steering wheel. Observe the steering shaft, sliding joint, universal joints and steering box input in sequence to locate the lost motion.
3. Measure axial and radial displacement relative to the column housing using a dial indicator. Apply the specified measuring load and compare the readings with the manufacturer's tolerances.
4. Check the full adjustment range and the locking mechanism in several positions. For pneumatic operation, measure the supply pressure with a pressure gauge in accordance with the workshop procedure and check the lines and control valve for leaks.
5. If a steering angle sensor is fitted, read the fault codes and live angle values. Check for sudden jumps or signal interruptions while turning slowly before replacing electronic components.

Replace deformed steering shafts, damaged splines and activated crash-energy-absorbing mechanisms; welding or straightening is not a safe repair method. Replace individual wear parts only when the manufacturer permits that repair. Overtightening pinch bolts will not restore a worn fit.

Before removal, follow the airbag deactivation procedure and observe the specified waiting time. Secure the steering wheel and clock spring in the centre position; do not allow them to rotate freely with the steering shafts disconnected. Install connections in the specified position, use new fasteners where required and observe tightening torques and any specified tightening angles. Afterwards, check for smooth operation, secure locking and adequate cable clearance. Perform a steering angle sensor calibration if specified and finish with a controlled road test.