BENDIX LQ-4 Handbuch - Seite 4

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INNER

PISTON

SPRING

(9)

INLET

EXHAUST

VALVES

(10)

™

FIGURE 7 - LQ-4

FRONT AXLE RATIO VALVE

PREVENTIVE MAINTENANCE

Important: Review the Bendix Warranty Policy before per-

forming any intrusive maintenance procedures. A warranty

may be voided if intrusive maintenance is performed during

the warranty period.

No two vehicles operate under identical conditions, as a

result, maintenance intervals may vary. Experience is a valu-

able guide in determining the best maintenance interval for

air brake system components. At a minimum, the valve

should be inspected every 6 months or 1500 operating hours,

whichever comes first, for proper operation. Should the valve

not meet the elements of the operational tests noted in this

document, further investigation and service of the valve may

be required.

SERVICE CHECKS

OPERATIONAL CHECKS

1. Install a test gauge or gauge of known accuracy in the

supply and delivery lines of the LQ valve.

2. Build system air pressure to governor cut-out, turn off

engine and apply parking brakes.

3. While making a slowly increasing service brake applica-

tion, note that the pressure registered on the gauge

installed in the delivery line from the LQ valve is approxi-

mately half the pressure registered on the gauge in the

COVER

(1)

O-RING (6)

OUTER

PISTON (4)

O-RING (7)

OUTER

PISTON

SPRING (5)

O-RING (8)

INNER PISTON (3)

BODY (2)

HOLD OFF

SPRING

(11)

supply line. The 50% reduction will occur while supply

line pressure is between 0 and 40 psi.

4. When the supply line pressure exceeds 40 psi, but is

below 60 psi, observe that the delivery line pressure is

no longer one half and that the delivery line pressure is

"catching up" to supply pressure.

5. When supply pressure exceeds 60 psi note that the

delivery line pressure is approximately equal.

Note: The pressures stated here are examples only.

Various piece numbers of the LQ valves may have

different pressure settings. For information on a specific

installation, consult the vehicle handbook.

LEAKAGE CHECKS

Make and hold a service brake application. Apply a soap

solution to the exhaust port and around the seam between

the cover and the body. Leakage equivalent to a 1" bubble in

5 seconds is permissible.

If the LQ valve does not function as described above or leak-

age is excessive, it is recommended that it be returned to

the nearest Bendix authorized outlet for a factory remanu-

factured valve under the Exchange Plan. If this is not possible,

the valve can be repaired with genuine Bendix parts, in which

case the following should prove helpful.

Note: Maintenance kits for the LQ-3

ratio valves are available from any authorized Bendix outlet.

REMOVAL

Apply the vehicle parking brakes. Identify and disconnect

the supply and delivery lines of the LQ valve. Remove the

two mounting bolts securing the LQ valve to the vehicle.

DISASSEMBLY

1. Prior to removing the four Phillips head screws and their

lockwashers which secure the cover to the body, mark

the relationship between the cover and the body.

2. Carefully separate the cover (1) (Figure 7) from the body

(2) and remove the inner (3) and outer pistons (4). (The

cover is under approximately 30 pound load from the

outer piston spring.)

3. Remove the outer piston spring (5).

4. Separate the inner and outer pistons.

5. Remove the o-ring (6) from the outer piston.

6. Remove the large (8) and small (7) diameter o-ring from

the inner piston.

7. (LQ-4

™

valve) Remove the inlet exhaust valve spring (9)

and inlet exhaust valve (10) from the inner piston.

Remove the hold-off spring (11) if present

8. (LQ-3

™

valve — Figure 8) Remove the retaining ring (1),

washer (2), inlet exhaust valve spring (3), and inlet

exhaust valve (4).

™

and LQ-4

front axle