Directions to Sepang
Take any major highway heading to Kuala Lumpur International Airport (KLIA). Turn before KLIA at the Sepang exit.Once you pay the toll at the traffic light turn right. Then, 1st roundabout 2nd exit turn in and followed by at the 2nd roundabout 2nd exit turn in. You will see the Mosque on your left and then before the traffic light turn left. At the roundabout get in the first exit. After that before the traffic light turn left. Keep right and look out for a small opening at the centre of the road and turn in, you'll see the pit lane.(Thanks to rc51vtrsp1 for the directions)
Alternatively;Take any major highway heading to Kuala Lumpur International Airport (KLIA). Once you pay the toll, take the first left exit from the highway. A mosque will be on your left.
At the round-a-bout, go straight. Take the first left exit after the first traffic light (about 8 km). Follow the signs to take you to your destination.
Attached is a map to Sepang: