BMW 7 Series: Mechanical Steering Gear

INFORMATION ON REPLACING STEERING BOX AFTER ACCIDENT DAMAGE

Situation

In the event of accidents or driving conditions similar to accidents, shock-like loads can cause different types of damage to steering boxes. When a steering box is externally undamaged, it is sometimes only possible to identify damage with great difficulty and with great effort. However, damage of this nature poses an unacceptable risk to the vehicle because it can result in failure of the steering system.

Because of the disproportionate amount of effort involved, it is generally not sensible to check thoroughly all the individual components of the steering box and as an alternative it is necessary to take into account other components which can be checked more easily.

Procedure

The steering box must be replaced if one or more of the following points apply:

A. Visible or noticeable damage to the steering box

• Version with electric steering box (EPS): Examine in particular the control unit with all plug connections for damage and hairline cracks.

B. Unacceptable torque increase and jamming when the steering box is turned from lock to lock (without hydraulic/electrical assistance)

C. Permissible tolerances exceeded during axle/wheel alignment (include alignment record with invoice/report if necessary)

D. Fire damage

E. Damage, permanent deformation or fractures to:

• Wheel rims in the event of a negative result from the wheel/axle alignment check
• Spring struts, steering stubs, wheel carriers
• Wishbones
• Leading or trailing links or anti-roll bars with this function
• Body-side screwing/attachment points for wheel guide/control components
• Front axle support
• Pitman arms
• Track rods
• Steering gear fixtures
• Steering Column

This guideline is binding for all accident repairs to BMW and MINI vehicles.

NOTE: If the steering box replacement work which is required for safety reasons is refused by the customer or an insurance company for cost reasons, a memorandum to that effect must be drawn up and countersigned by the party bearing the costs of the accident repair.

IMPORTANT: The vehicle's operating licence will be invalidated whenever the function of any of its safety components is compromised!

NOTES ON CHECKING STEERING BACKLASH ON VEHICLES WITH RACK-AND-PINION STEERING

NOTE: The evaluation "steering backlash" is made usually when the front axle is raised, where the track rod is angled.

The force introduced via the track rod is divided into a horizontal force and a vertical force relieving the thrust member (1) against the spring (2).

The steering box is depressurized on account of no hydraulic assistance due to engine standstill and is thus not preloaded! The play created in this way is incorrectly referred to as steering backlash.

Fig. 35: Identifying Thrust Member, Spring And Rack

3 = Rack

Solution

1. Check the tie rod backlash only in loaded condition or in the design position.

2. Checking with front axle raised:

• To evaluate the backlash of the tie rod bearings on the steering box side, it is necessary to pressures the steering box via its servo system!
• The combustion engine must be running during hydraulically assisted steering for this purpose
• For electro-hydraulic steering servo systems, the ignition must be on
• In the case of solely electric steering servo, the ignition should also be switched on so that the steering shaft is subjected to load.

Desired state

The steering must be backlash-free in all components!

REPLACING GAITER FOR STEERING BOX ON LEFT OR RIGHT

IMPORTANT: The hydraulic steering gear must be replaced if the polished surface of the rack is damaged (e.g. by corrosion)!

Necessary preliminary work

• Remove TRACK ROD END
• Remove UNDERBODY PROTECTION

Clean track rod.

Release band clamp (1) and EAR CLIP (3).

Detach gaiter (2) from track rod.

Installation note: Clean rack and check surface for damage (e.g. by corrosion).

Grease rack (refer to STEERING AND WHEEL ALIGNMENT - OPERATING FLUIDS ).

Clean track rod and apply grease to taper.

NOTE: This ensures that the gaiter is not rotated when the track rod is rotated.

Fig. 36: Identifying Track Rod Clamp, Gaiter And Ear Clip

After installation

• Perform CHASSIS/WHEEL ALIGNMENT CHECK

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