Hydraulic Pump - Replacement
88audi03Applies To: ALL 5000 from 1984 model year
Subject: Central Hydraulic System (Supercedes Product Circular, Group 48, No. 87-11, October 12, 1987)
Number: Group:
88-05
March 7, 1988 48
Brakes - Steering
Whenever the hydraulic pump is replaced, the following requirements must be met to ensure proper system operation.
^ hydraulic pump must be properly filled and primed prior to operation (on workbench)
^ the fluid reservoir strainer must be cleaned
^ the banjo bolt with screen at the accumulator must be replaced
^ correct banjo bolts must be used at the pump fittings (depends on pump tag color and code number on pump tag)
CAUTION
Always replace banjo bolts at the hydraulic pump.
Follow the procedure below to correctly replace the hydraulic pump.
Central hydraulic pump, replacing
Work sequence
- prior to removing old pump, bleed the hydraulic accumulator by pumping the brake pedal 20 to 25 times with the engine off
- loosen pump pulley bolts and pump bracket bolts
- remove hydraulic lines from pump
- remove pump from vehicle with brackets and pulley attached
- unbolt return line from hydraulic brake servo to reservoir at the servo (arrow A)
- remove clamp from steering gear return hose at reservoir and carefully pull hose off (arrow B)
- remove nuts and washers holding reservoir bracket to engine compartment panel and pull reservoir assembly out toward front of vehicle
- unfasten accumulator hose at bottom of reservoir and pull hose off (arrow C)
- remove reservoir with bracket and two hoses attached
- wash out reservoir and attached hoses, strainer, and banjo bolts with clean solvent
CAUTION
Do not use solvent which could damage rubber hoses or seals when cleaning hydraulic system components.
Use only clean solvent.
Note
If the strainer cannot be thoroughly cleaned, or is damaged, replace it with a new part. Use the newer version strainer, Part No. 443 422 385A.
- install reservoir assembly in vehicle and attach hoses and lines disconnected during removal
Hydraulic pump, priming:
Note
On new or replacement pumps, read procedure described on pink tag supplied in the box.
CAUTION
Part Numbers may be different for different models, model years and options. Always consult with the Parts Dept. for correct application.
- assemble pump brackets and pulley to new pump
CAUTION
Use only hydraulic fluid, Part No. G 002 000.
- pour some hydraulic fluid into outlet port (arrow A) and rear chamber (arrow C) of new pump
- fill suction chamber (arrow B) with hydraulic fluid
- rotate pump slowly by hand through four to five complete revolutions (fluid will be discharged at arrow C). Keep suction chamber (arrow B) full of fluid
- install new hydraulic pump in vehicle
- separate pump to accumulator line at fitting and check if damper hose is missing or restricted
- remove banjo bolt at accumulator and replace
- reassemble accumulator line and connect to pump
- connect pressure line to pump using correct banjo bolt:
^ pump with red tag:
use banjo bolt with small hole Part No. N 903 246.01
^ pump with sliver tag:
use banjo bolt with three large holes and no screen Part No. N 021 071 2
- connect suction line to pump using correct banjo bolt:
^ pump with red tag:
use Part No. N 902 669.01 (identified with 2 grooves on bolt head)
^ pump with silver tag:
use Part No. from chart below
- tighten suction line banjo bolt to 40 N-m (29 ft.lb.)
- fill reservoir with hydraulic fluid, Part No. G 002 000
Pump operation, checking
CAUTION
Do not turn the front wheels unless the hydraulic system is filled with fluid. Damage to the steering rack could result if wheels are turned after the hydraulic system has been emptied.
- start engine while holding brake pedal down firmly
Note
The brake pedal will be drawn down by hydraulic pressure when the brake portion of the pump begins to operate.
- if brake pedal does not go down in 30 seconds, stop engine and let vehicle sit for 30-45 seconds
Note
Several attempts may be necessary before the brake pedal goes down.
CAUTION
DO NOT continue to operate engine if brake pedal does not go down in 30 seconds. Damage to the hydraulic pump will result if this step is not followed.
- repeat pump operation checking procedure
- inspect all hoses and fittings for leaks
- bleed steering system by turning steering wheel lock to lock several times quickly
- add more hydraulic fluid if level drops below "MAX" marking
Note
Reservoir must be free of air bubbles when steering wheel is turned.
Labor operation 48 98 210
Repair: 130
Quality check: 10
Total: 140