Brake System

Page 34

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Volvo Bus Service and Maintenance Manual

 Electrical retarder
64 Check attachments and electrical connections.
Clean outside by flushing with water.
Check control unit attachments and draining.
 Hydraulic retarder
 (Voith VHBK 130 L/130 F)
65 Check the control pressure. If necessary adjust the relief valve, opening pressure approx. 30 kPa above maximum control pressure.

Electrical retarder

With the retarder cold, wash off any dirt on the outside with water at a pressure of 8-10 kgf/cm2. After washing, blow-dry with pressurized air.

Too much grease on the electrical retarder can often result in odours when the retarder heats up.

Note: When Supertelmaco no. 3 is used, the greasing interval can be extended to 40,000 km, provided that this grease is not mixed with any other type of grease.

Electrical retarder control unit drain hole
Drain hole, control unit

Function check

The retarder can be tested driving on the road. Set the switch, in the pedal-controlled system, to the "on" position. Increase speed to about 70 km/h and depress the brake pedal approx. 9-12 mm (or move the hand control to the first step). Check/feel that braking has started.

Apply the retarder a step further and check that the braking increases. With the pedal-control system, the retarder reaches full application and the brake torque is approx. 1500 Nm. When the retarder is cold, the brake pedal will be depressed approx. 27-31 mm, which corresponds to a brake application of 20-50 kPa.

Brake pedal positions with pedal-controlled retarder operation
Brake pedal positions with pedal-controlled retarder operation

Hydraulic retarder

Like the electrical retarder, the hydraulic retarder can be tested driving on the road or on a vehicle dynamometer. A brake tester cannot be used.

Voith VHBK 130 L (C10M)

Max. braking torque at 120 kPa operating air pressure is 2200 Nm.

Voith VHBK 130 F (B10M chassis no. 20001-)

Max. braking torque at rear axle reduction ratio 3.10 and 3.56:1 is 3000 Nm at 180 kPa operating pressure. Other rear axle reduction ratios, max. 2400 Nm at 140 kPa operating air pressure.

Concerning checking and adjusting operating air pressure/relief valve, refer to Service Manuals, Sections 5(59) and 0(03).