Balance Shaft Oil Seal Replacement

Introduction

This procedure provides instructions for replacing the balance shaft seals on a 944. It also provides instructions for resealing the balance shaft cover.

At the back of the balance shaft housing there is a large-diameter plug that uses an O-ring to seal the rear of the housing. It is not recommended to replace this O-ring or reseal the balance shaft cover unless they are actually leaking, as removing the balance shaft covers requires significant disassembly — particularly on turbocharged cars.

On 1985½ and newer models, there is a seal between the upper balance shaft bearing cap and cover. This seal directs oil flow from the upper balance shaft bearing to a fitting on the balance shaft cover that supplies the turbocharger on turbocharged cars. Normally aspirated cars use the same bearing cap but the cover is not tapped for a turbocharger oil supply fitting. The seal must be installed to ensure adequate lubrication of the upper balance shaft bearing. If the balance shaft cover needs to be resealed or the rear sealing plug O-ring replaced, this bearing cap-to-cover seal must also be replaced. (This does not apply to models through early 1985 as the bearing cap is machined integral to the balance shaft cover.)

Tools

• Jack stands
• Floor jack
• Metric socket set
• Metric wrench set
• Porsche Timing Belt Tension tool (P9201)
• Flywheel Lock (P9206)
• Balance Shaft Pin Spanner (P9200) or equivalent
• Gear puller
• Seal puller
• Small screwdriver or probe
• Bearing grease
• Loctite 574 and velour roller (if balance shaft cover is removed)

Other Procedures Needed

• ENG-03: Flywheel Lock Installation
• ENG-13: Locating and Setting Engine to Top Dead Center (TDC), Cylinder 1
• AF-01: Air Filter Housing and Air Flow Sensor — Removal and Installation
• ENG-05: Camshaft and Balance Shaft Belt Removal
• ENG-06: Camshaft and Balance Shaft Belt Installation
• ENG-10: Camshaft and Balance Shaft Belt Tension — Checking and Adjusting
• ENG-08: Balance Shaft Sprocket Installation and Alignment

Procedure

Note: It is possible to remove the camshaft belt without removing the crankshaft gear. However, to replace the water pump, balance shaft seals, or front crankshaft oil seal, the crankshaft gear must be removed.

1. Using ENG-05, remove the camshaft and balance shaft belts, all rollers, tensioners, balance shaft sprockets, crankshaft gears, and rear timing cover.
2. Remove the woodruff key from the slot in the balance shaft.
3. Remove the retaining bolts (3) that hold the front balance shaft support in place and slide the support off the end of the balance shaft.
4. If the balance shaft cover needs to be resealed or the rear plug O-ring needs to be replaced, remove the balance shaft cover bolts and remove the cover and rear plug.
5. Using a seal puller, remove the main seals from the front of the balance shaft support. If a seal puller is not available, slide a screwdriver under the inside lip of the seal and pry the seal out of the support.
6. Remove the spacer from the balance shaft support.
7. Using a small screwdriver or probe, remove the large O-ring from the balance shaft support.
8. Apply a thin coat of bearing grease to the O-ring groove in the balance shaft support, install the O-ring, and apply a thin coat of bearing grease to the outside of the O-ring.
9. Apply a thin coat of bearing grease to the contact surfaces of the support spacer and install the spacer into the support housing.

Caution: Although the main balance shaft seals appear identical, there is a 1 mm difference in the outside diameter between the two seals. Do not confuse them or the job will have to be redone.

10. Apply a thin coat of bearing grease to the sealing surfaces of the main balance shaft seal and slide the seal into the front of the support. Tap the seal into place using a socket of slightly smaller outside diameter than the seal.
11. If the balance shaft cover has been removed, perform the following: a. Install a new O-ring onto the rear housing plug and position the plug into the housing. b. Apply a thin coat of Loctite 574 to the cover mating surface using a velour roller. Position the cover in place on the balance shaft housing. c. Install the balance shaft cover retaining bolts finger tight. Do not torque until front support is installed.
12. Install the thin plastic seal onto the end of the balance shaft.
13. Install the front support (with spacer and seal installed) onto the balance shaft and slide into the front of the housing until fully seated.
14. Install the front support retaining bolts (3) finger tight.
15. If the balance shaft cover was removed, torque the cover retaining bolts per the applicable diagram and sequence for your vehicle:
    • Lower Balance Shaft (1983–1985)
    • Lower Balance Shaft (1985½–1987)
    • Lower Balance Shaft (1987–on)
    • Upper Balance Shaft (1983–1985)
    • Upper Balance Shaft (1985½–on)
16. Torque the front support bolts (M8) to 20 Nm (15 ft-lbs).
17. Using ENG-06, install and tension the balance shaft and camshaft belts.