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Rear Main Seal Replacement
 
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Pelican Technical Article:

Rear Main Seal Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$20 to $40

Talent:

**

Tools:

12mm 12 point, large drain pan, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

Porsche 944 (1983-89)
Porsche 944 S2 (1989-91)
Porsche 944 Turbo (1986-89)
Porsche 944S (1987-88)

Parts Required:

Rear main seal, flywheel bolts

Hot Tip:

Dry seat the seal

Performance Gain:

No oil leak

Complementary Modification:

Resurface the flywheel

So your rear main seal is starting to leak oil and needs to be replaced. This is not a good thing to leave unattended. While the rear main seal is easy to replace, getting to it will involve removing everything needed to perform a clutch job and then some. The only good thing about it is if you don't replace it soon enough you will end up needing to perform a clutch job, as the oil will eventually destroy your clutch and flywheel.

Please see our article on clutch replacement for all the additional steps needed to perform before getting to the rear main seal. In addition to the clutch work you will also need to drain the engine oil, so please see our article on engine oil and filter replacement.

The rear main seal is located behind the flywheel (red arrow); this means you will need to remove the flywheel to change the seal.
Figure 1

The rear main seal is located behind the flywheel (red arrow); this means you will need to remove the flywheel to change the seal. The flywheel bolts are single use only. Make sure to order new flywheel bolts when ordering your seal. Do NOT reinstall the old bolts.

You will need a flywheel lock to remove the bolts.
Figure 2

You will need a flywheel lock to remove the bolts. You can improvise one yourself by reinstalling a pressure plate bolt (red arrow) and a bell-housing bolt (yellow arrow) and then slipping a boxed end wrench over them.

You will need to wake up the bolts by placing the 12mm 12 point socket into the bolt head (red arrow) and tapping each one with a hammer several times.
Figure 3

You will need to "wake up" the bolts by placing the 12mm 12 point socket into the bolt head (red arrow) and tapping each one with a hammer several times.

Making sure that the socket is well seated, break each bolt loose in a crisscross pattern.
Figure 4

Making sure that the socket is well seated, break each bolt loose in a crisscross pattern. You do not want to strip these bolts, so take your time and make sure the bolts have been woken up and that the socket is well seated and that there is no grease or dirt on the socket. Use care when removing the last bolt, as the flywheel is free and can fall. The flywheel is heavy, so make sure to have two hands on it. If your flywheel does not come off easily, gently tap it with the side of your fist. In a worst case scenario you can gently pry it with a large screwdriver between the outside of the wheel and the case.

There is a locating pin on the mount that insures the flywheel can only be mounted in one way, so be aware of this when reinstalling.
Figure 5

There is a locating pin on the mount that insures the flywheel can only be mounted in one way, so be aware of this when reinstalling.

There is a small notch in the area around the seal that you can use a screwdriver in to pry out the old seal (red arrow).
Figure 6

There is a small notch in the area around the seal that you can use a screwdriver in to pry out the old seal (red arrow). Do not jam anything metal or sharp between the seal, mount and case as this can cause scratches and lead to leaks even with a new seal.

I like to dry seat the new seal as there is usually a very fine film of oil on the end of the crankshaft mount to lubricate the inside of the seal.
Figure 7

I like to dry seat the new seal as there is usually a very fine film of oil on the end of the crankshaft mount to lubricate the inside of the seal. Make sure the seal is facing the right direction with the lip side in and the flat side facing out (red arrow).

Make sure the mounting area is clean and dry.
Figure 8

Make sure the mounting area is clean and dry. You can use a piece of PVC pipe or if you have a bearing puller kit you can usually find a puller with the same outside diameter of the seal and tap it evenly into place (red arrow). Some people swear you can gently tap it in place by using a piece of 2X4 and going slowly around the outside diameter. Whichever means you use the seal must be installed smoothly and evenly. If you bend the metal around the outside of the seal you will need to remove it and replace the seal again with a new one.

The seal is seated when it is flush with the case (red arrow).
Figure 9

The seal is seated when it is flush with the case (red arrow). Installation is the reverse of removal.

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