Power Steering - Noise from Hydraulic System

Group
4

Number
9402

Model
6 Cyl.

Part Identifier
4890

January 11, 1994

Subject:
Noise from Power Steering
Hydraulic System

ATTENTION: Service Manager / Service Technician

Models Affected:

911 Carrera 2/4/Turbo, up to 1994

Concern:

Some customers may complain of noises from the power steering hydraulic system.

General Information:

Since model year 1992, the above mentioned vehicles have used a rotary valve power steering rack instead of the piston valve system used previously. When the rotary valve steering rack is installed, hydraulic noise may occur due to tolerances in the pressure and return pipes of the steering system. The rotary valve steering rack has been used in production since July 19, 1991 from the following VIN'S:

968 NS 42 0179
966 NS 44 0094
969 NS 46 0201
968 NS 48 0210





Power steering rack Identification: (Figures 1 and 2)

To correct a customer complaint of hydraulic noises from the steering system when the steering system has no defects, the pressure and return lines should be replaced. This applies to all 911 C2 and Turbos only. The new type pressure and return lines are the same as used on the 911 Carrera (993) and are fitted with additional expansion hoses.

IMPORTANT NOTE:
Carrera 4
The 911 Carrera 4 cannot be fitted with the new type pressure and return lines due to lack of space (front differential); therefore, a new piston valve steering rack must be installed. (See Parts Information)





Parts Information:

Repair Time Allowance:
Modify power steering Includes:
Replace pressure and return pipes, install new mount in center tunnel, and bleed steering system.

Model Damage Code
911 Carrera 2/Turbo 48 90 31 00 170TU
911 Carrera 4 48 90 19 00 330TU

Reference:
911 Carrera 2/4 Repair Manual, Vol. IV.

Repair Procedure:





Disconnect pressure and return pipes from steering gear (arrows) and remove the pipes (Figure 4).





Remove old pipe mount from steering gear. Fit new mount, Part Number 993 347 473 00 (arrow C), install plastic clip from old mount on new part (arrow D, Figure 5).

Note:
Due to changes in the pipes, the old pipe mount in the center tunnel can no longer be used.





Fit new mount. To do so, drill a 5 mm dia. hole. (For dimensions, see Figure 6). Fit pop rivet with stud bolt (8 mm long, 5 mm dia. from pop rivet repair set, Part Number 944 501 941 00, using a pop rivet tool. The mounting sleeve included in the repair kit must be pushed over the stud bolt.

Saw off old stud bolt and treat bare metal with anticorrosion paint.

Screw pressure and return pipes to steering gear using the banjo bolts and new sealing rings (arrow E). Only tighten banjo bolts slightly.





Clip pipes to mount (arrow F). Screw mount to pressure line together with hose clamp for return line (arrow G, Figure 7).

Connect the pressure and return lines (arrow H) in the center tunnel. Secure the suction line (arrow 1) with a hose clamp.





Install new mount (rubber mount and hose clamp) on the new stud bolt which you have just riveted into place (arrow K, Figure 8).

Tighten all pipe connections with the specified tightening torque:
Pressure and return pipe to steering gear 20 N-m
Pressure pipe connection in center tunnel 25 N-m

Top up hydraulic fluid and bleed steering system in accordance with instructions in 911 Carrera 2/4 Repair Manual, Vol. IV, page 48-2.

Check all pipe connections for leaks and install underbody panel.