My car is a 1997 Nissan Sentra B14 (Series 3) Super Saloon Model, I have been topping up my oil 4 the past 2 years and been oil dripping a 25c size on the floor until It got worse....

Then I read some of the DIY in the NISSAN FORUMS site and did the oil seal replacement my self.

Here are the steps I did:

1. Remove the drive belts.

2. Place a 27mm Socket Breaker bar on crankshaft pulley. Then start the engine then you'll hear the screw loosen up then turn the engine off.

3. Remove the pulley with a pulley puller or you may remove it with your hand.

Then you'll see this..:





That's how my engine looks like. hehehe

Here are the pic of the new and old seals:



close up:



4. In placing the seal get a socket of a piece of wood as big as the seal and hammer it into place.

5. Then clean the area with gasoline or any engine de greaser.

6. Replace the pulley, hammer it in. And replace the screw, hammer the wrench untik screw is tight. (place the car on 4th gear so that crankshaft will not move.)

7. Then replace the belts.

And you are good to go.

Here's one sample.

Enjoy!

[ame="http://www.youtube.com/watch?v=rYTDMwxw4Ds"]YouTube- Front Crankshaft Oil Seal Replacement[/ame]