The oil pan flange is installed on a sealant, there is no gasket. Therefore, if there is an oil leak in the oil pan and cylinder block connector, tightening the oil pan mounting bolts will not lead to the desired result. It is necessary to remove the oil pan and replace its seal.
1. Place the vehicle on a lift or inspection pit.
2. Drain the oil from the engine.
3. Remove the exhaust pipe (see "Replacing the intake pipe").
4. Remove the three bolts securing the oil pan to the clutch housing...
5. ...bolts securing the oil pan to the cylinder block...
6. ...and remove the crankcase.
7. If necessary, remove the oil deflector shield by unscrewing the bolts securing the shield to the oil pan...
8. ...and remove the shield.
9. Clean the mating surfaces of the cylinder block from old sealant...
10. ...and the oil pan.
11. Apply a special sealant to the mating surface of the oil pan (MS 721-40A or its equivalent) with a 4 mm diameter roller, and the line of sealant application should be on the inside of the mounting holes.
12. After 5 minutes of applying the sealant, install the oil pan on the cylinder block, screw in the pan mounting bolts and tighten them to the torque specified in Appendix 1.
13. Install all removed parts and assemblies in the reverse order of removal.
14. Fill the engine with oil (see "Changing engine oil and oil filter").
NOTE: You can add oil and start the engine no earlier than half an hour after installing the oil pan; this time is necessary for the sealant to polymerize.
(Original version of the article on the website: ChevyMan)