Page 58 - National Express_ GMStands

1.8 Drive Shaft

No parts of the drive shaft [drive cylinder, control cylinder, pump, hoses and pipes] should have leaks of any
kind as it’s a closed circuit that works under pressure.
The bushings should never show signs of dripping oil.

Worn or cracked ball bearings could block the affected wheel or it may become detached from its bushing.

A ball bearing that is too loose or beyond the tolerance limits means it is worn and should be replaced.
If the steering ball-and-socket joints are over 2mm loose, this could cause the loss of steering power and an
accident.

A fault in the drive shaft rotation sensor will affect the steering and the ESP [stability control].

1.9 Tyres

A vehicle should never be driven if the wheel pressure on one of the shafts is lower than the levels
recommended by the vehicle’s manufacturer.

Tyres with lacerations, on the sidewalls or on the tread, could make the tyre burst while driving.

If the tyre pattern is worn to less than manufacturer requirements (Standard 1. Wheel, tyre fitment and
security), it could lose grip under bad weather conditions or on low adherence road surfaces.

1.10 Pneumatic Circuit

A pneumatic circuit with leaks could render the brake system or the suspension system useless, and affect other
systems too. The team manager will appraise the fault and how it could affect the vehicle’s safety systems.

The vehicle should never be driven if the pressure is under minimum requirements of the manufacturer.
If the pressure is lower than the suitable level in certain adherence conditions, the shaft could stop working as it
should and make the driver lose control of the vehicle.
The team manager will value the fault and will determine the urgency of the intervention.

Too much air in the pneumatic circuit could make the brake system fail and cause cracks at the weakest points
in the circuit.
If the air pressure is below the manufacturer’s recommendations, the systems that need the air pressure will not
work as expected and will cause the brake system, the suspension system or another system to fail.

1.11 Electric Circuit

The ignition for the steering column should be in good working order and should never be hotwired or broken. All
the services provided by this element in each of its positions should be in good working order.
The alternator belt is broken and is not independent.

All the parts in the electric system must be in good working order.
The fuses, which protect the electric circuit, should never be hotwired and should be the right type and value
for each case.
All outside lights in the vehicle should be in good working order.

Global Maintenance Standard: Safety Critical Defects 7