Power Steering Rack Rebuild (Reseal)

Introduction

Procedure contributed by Karl "Doc" Wilen.

This procedure covers the complete disassembly and reseal of the Porsche 944 / 944S power steering rack. A leaking rack does not always require replacement — if the rack body and steering gear are in good condition, installing a seal kit can restore proper function at considerably lower cost and effort than full replacement.

Before beginning this procedure, the rack must be removed from the vehicle. Refer to STEER-01 for the rack removal procedure.

Seal kits for this procedure are available from Porsche-specialty parts suppliers. A rebuilt rack with core exchange is also an option if the rebuild is not feasible.

Note: This is a detailed, time-consuming procedure. Set aside adequate bench time and work in a clean environment to avoid contaminating the seals.

Tools

• Metric socket set
• Long socket extensions
• Small pick (a dental pick is ideal)
• Hammer
• Punch
• Needle nose pliers
• 6mm Allen key
• Reseal kit specific to the 944 rack

Procedure

Rack Disassembly

1. With the rack secured on the bench, remove the hard lines using the 6 mm Allen key. These fittings can be very tight. The hard lines must come off because each fitting has two rubber o-rings that need to be replaced — eight o-rings in total across the four fittings.

2. Locate the locking collar that holds the two halves of the rack together. The collar unscrews off the bronze steering sleeve; slide it back along the sleeve to separate the bronze sleeve from the control tower and expose the control tower.

3. Remove the rubber boot from the top of the control tower where it surrounds the spindle, then remove the three 10 mm bolts that retain the top cap. With the bolts out, carefully pry the cap off the control tower. The cap contains one wiper seal and an o-ring. Note the orientation of the wiper seal before removing it: the groove side faces in toward the inside of the tower, with the flat side pointing outward.

4. Carefully disassemble the rack internals. The major components are:

   • Shuttle — the sliding hydraulic piston
   • Steering rod — connects shuttle to the rack output
   • Steering gear — the pinion and associated valve body
   • Control tower — the central hydraulic control housing
   • Steering sleeve (bronze) — the outer sleeve around the steering shaft

   Lay each component out in order as it is removed.

Steering Gear Seal Replacement

5. Inspect the steering gear o-rings. On original racks, these are typically white hard plastic rings. The reseal kit provides blue plastic rings over rubber o-rings as the replacement. Remove all old rings and o-rings from the grooves on the steering gear using the small pick. Take care not to scratch the sealing surfaces.

6. Install the new rubber o-rings in each groove, then seat the new blue plastic rings over the top of the o-rings. Ensure the plastic rings are fully seated without gaps.

Control Tower Seal Replacement

7. The control tower contains wiper seals on both the driver's side and passenger's side. Begin with the bottom wiper seal on the driver's side — this is one of the most critical seals in the rack, as it keeps fluid from leaking out of the rack on the driver's side.

   Using the small pick, carefully remove the old wiper seal from the driver's-side bore of the control tower bottom. This is the hardest seal to remove, because there is no room to drive it out with a socket — it may have to be destroyed to get it out. Note the orientation of the seal before removal: the groove side faces upward as you look down at the seal from the top.

   Caution: Take great care not to nick the metal casing of the control tower bore while removing this seal. If the casing is nicked, the rack will most likely leak once it is back in the car, and a rebuilt rack will be the only fix.

8. Move to the passenger side of the control tower. Here you will find a large o-ring seated in an external groove, and a separate shuttle o-ring. Remove both old o-rings using the pick and replace with the new o-rings from the kit.

Steering Shaft and Shuttle Seal Replacement

9. Inspect the steering shaft and shuttle assembly. To free the shuttle from the steering shaft, remove the two snap rings, the washers, and the seal mechanism. There are two o-rings located underneath the shuttle seal mechanism, and a further two o-rings under the washers; remove and replace all of these o-rings.

10. The shuttle interior contains a wiper seal and a hard plastic spacer. Remove the old wiper seal using the pick. The plastic spacer may be reusable if undamaged — inspect it carefully. The groove side of this wiper seal faces out, toward the passenger side of the vehicle.

11. On the outside of the shuttle, locate the hard plastic ring. The replacement o-ring from the kit installs on the outer side of this ring, not between the ring and the shuttle body.

Bronze Steering Sleeve Seal Replacement

12. The bronze steering sleeve contains a wiper seal, a plastic spacer, and a plastic guide ring. These are accessible after the sleeve is removed from the rack body. Remove the plastic guide ring first using the small pick and needle nose pliers, then extract the old wiper seal and inspect the spacer and guide ring.

13. Work the old wiper seal and spacer out of the bronze sleeve. Use the pick carefully to avoid scratching the bore.

14. When installing the new wiper seal into the bronze sleeve, pay close attention to orientation. The groove side of the seal faces toward the control tower, that is, toward the driver's side of the vehicle.

    Caution: Install each seal in the correct direction. A seal pressed in the wrong way around will leak. Verify orientation against the reseal kit instructions before pressing the seal home, and drive the seal in evenly using a correctly sized socket.

Rack Reassembly

15. Reassemble all components in reverse order of disassembly. Work cleanly — lubricate new seals and o-rings lightly with clean ATF before installation. Do not use petroleum-based grease on rubber seals.

16. Screw the locking collar back onto the bronze steering sleeve and ensure it is positioned correctly to lock the two halves of the rack together.

17. Reinstall the control tower top cap, refit the rubber boot, and secure the cap with its three 10 mm bolts.

18. Once fully reassembled, reinstall the rack in the vehicle per STEER-01. Bleed the power steering system fully and check for leaks.

Note: A successfully resealed rack should have no external leaking at the sleeve or control tower. If leaks persist after the reseal, inspect the rack body itself for cracks or porosity.