Steering and Suspension

Page 43

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Volvo Bus Service and Maintenance Manual

 Levelling valves
88 Check to make sure that the mountings for the levelling valves are tight.
 Clean the air filter and the strainer in the check valve (early prod.) type.
 Check and if necessary remedy any leakage at the connections.
 
 Kneeling system ("KNG", "T-KNG")
89 Start the engine and check the kneeling function from underneath to make sure that no parts are binding. Check to make sure that the kneeling and rising are normal.
 

Levelling valves

Inspect the valves for loose joints, bent control rods and oil or air leaks.

The early prod. type levelling valves have a damping section which is filled with oil (silicone oil MIL-C-5606). If this leaks this will impair the delaying function which is required to prevent the levelling valve from reacting to every bump or hole in the road. Clean the air cleaner in white spirit and then blow dry and moisten with oil.

On buses with manual level raising, the working cylinders must be able to raise the body a prescribed distance from the ground clearance level.

Suspension bellow height
1Air filter
2Damper cylinder
3Inductive senders (kneeling)
4Working cylinder for level raising
ADistance sender - plate:
 2.5-3.5 mm, flat plate
 0.5-1.0 mm, plate with carrier edge

Kneeling system

As a variant to the "KNG", "T-KNG" systems, city and long-distance buses have a kneeling system that facilitates boarding at bus stops. The kneeling function is operated by a switch on the instrument panel, see further Service Manuals, Section 3-37 and Section 7.

The kneeling is achieved by the air bellows at the front entrance door being rapidly discharged via a solenoid valve in the line between the air bellows and the front axle levelling valve. During kneeling, separate solenoid valves block the air bellows on the opposite side of the front axle and also the feed line to the levelling valve.

An extra, 25 litre air tank is required for the bus to return rapidly to the drive position after boarding.

WARNING! Make sure the bus is properly jacked up or placed over a pit when checking the kneeling system, otherwise there may not be enough room to use a dolly or lie underneath the bus when air is drained from the front air suspension bellows.

When the kneeling system is activated, in certain cases the service brakes should automatically brake the bus so that it cannot be driven.

With the flat type plate the distance (A) between the inductive sender and the indicator plate should be 2.5-3.5 mm. For a plate with a carrier edge, the distance should be less: 0.5-1.0 mm. To adjust, move the inductive sender in its attachment bracket.

Inductive sender, level position
Inductive sender,level position ("2052", "2053")

 

Solenoid valves
Solenoid valves:feed system ("6001")
 filling kneeling bellows ("6006")
 discharging kneeling bellows ("6005A")