Test Driving Procedures

Page 6

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Volvo Bus Service and Maintenance Manual

Test driving procedures

Check the following:Instruments
 Observe that the gauges and direction indicators are operating correctly.
 Steering
 Check that the steering feels normal.
 Brakes
 Check that the brakes operate correctly.
 Check the control function of the ABS-lamp (bus with anti-lock brakes).

Instruments

Check:

-Oil pressure warning lamp goes out as the engine starts.
-Coolant level warning lamp should light one second after the starting key (switch) has been switched on.
-Parking brake warning lamp should light when the parking brake is applied. When the parking brake is released, the lamp should remain on until pressure reaches approx. 510 kPa (5.1 .kgf/cm2).
-Warning lamp for service. brakes should light when pressure in circuit reservoirs is below 380-460 kPa (3.8-4.6 kgf/cm2).
-Alternator warning lamp should go out as soon as the engine starts.

Check the kilometre meter (on certain buses) by inserting a paper slip for-stamping before test driving. After the test drive, re-stamp the paper slip to check that the counter unit is working.

Check that the speedometer/tachograph, tripmeter and speed limiter (if fitted) function. An incorrectly functioning tripmeter will influence results if used for calculating the fuel consumption.

Steering

Drive the bus slowly and turn the steering wheel to check that the steering feels normal. Check for wheel vibrations that indicate imbalance, for steering-wheel shimmy and for heavy steering. Steer the bus so that the front wheels run over holes in the road. Check that the bus runs straight ahead. Listen for unusual noises.

Brakes

Check that the brakes operate correctly and neither pull nor grab. Make sure all brake gauges stay in the normal range. Check the parking brake. Check its efficiency by cautiously driving the bus with the parking brake on. Check the blocking valve function by draining the pressure in the brake system to below 340-400 kPa (3.4-4.0 kgf/cm2).

Bus with anti-lock brakes (ABS):

Before starting the engine check that the ABS indicator lamp lights when the feed current is switched on. Check during starting that the lamp goes out at a speed of 7-8 km/h. The lamp should remain out until the engine stops.

If fitted, check that the retarder brake and/or exhaust brake function. (See pages 15 and 34.)

Power transmission

Check gearbox function and that the gear-change points are correct, see overleaf. For buses with manual gearbox: check de-clutch, pedal play (4-5 mm), check for stiffness and that the gear-change is smooth.