BENDIX BW1399 User Manual

2. With the engine idling, apply and release the brakes several

times. Note that the pressure is registered on the gauge with the

brakes applied and that each time the brakes are released the

gauge returns to 0 p.s.i. NOTE: In systems where a residual

check valve is used the pressure will not return to 0 p.s.i.

Between 3 and 50 p.s.i. pressure will remain when the brakes

are released. RESIDUAL CHECK VALVES MUST NOT BE

USED TO HOLD PRESSURE ON A DISC BRAKE CALIPER.

3. With the engine idling make a rapid, full brake application and

hold it applied while observing one of four gauge reactions.

Hydraulic System Okay

Problem is most likely in

Foundation Brakes

Check Foundation Brakes Mechanical Parts

For Example: (1) Drum or rotor condition

(2) Backing or anchor plate 

condition

(3) Shoe and lining condition

(4) Correct lining friction

(5) Caliper sliding surfaces

(6) Worn, missing or damaged

part

(7) Wheel bearings

Hydraulic System Okay

Problem is most likely in

Vacuum System or Booster

Perform Phase III Vacuum System Tests

While applying and releasing brakes, inspect hydraulic

lines and hoses for kinks, bends, "ballooning" and

restrictions that may not have been found in Phase I

inspections. Replace as necessary.

Release brake application, then remove atmospheric air

hose from vacuum booster control valve. (NOTE: This is

the hose running between the booster and its externally

mounted filter generally found in the cab.) Make a full and

rapid brake application and again observe gauge at wheel.

Hydraulic pressure rises

instantly to between 1000

and 2000 p.s.i.

Hydraulic pressure rises

slowly to same pressure

recorded above.

Repair or replace atmos-

pheric air filter and/or

connecting hose fittings.

Return to beginning of

Step 3 and retest.

Perform Phase III Vacuum

System Tests