Rear Crankshaft Main Bearing Seal: Service and Repair

Fig. 9 Rear main oil seal installation. 1983 & early production 1984:

A new, one piece, rear crankshaft oil seal has been introduced for 1984 4-121 engines. As this new seal has been proven effective in correcting rear main seal oil leaks, this seal should be used to replace the two piece seal on 1983 4-121 engines. Use of the two piece seal should be discontinued when servicing these engines.
Early production 4-121 engines installed in 1984 vehicles were assembled with a thin, one piece rear main oil seal, service P/N 14081761, which is also suitable for installation in 4-121 engines used in 1983 vehicles. Beginning with December 1983 production, 4-121 engines are equipped with a thick one piece seal, service P/N 14085829. As these seals are not interchangeable, 4-121 engines installed in 1984 vehicles must be inspected for an identification mark stamped on the left rear engine block boss, Fig. 9. Engines without an oval stamping in this area must be serviced with the thin, one piece seal, while engines with an oval stamping in this area must be serviced with the thick seal. Service replacement procedures for the two types of rear main oil seals are outlined below.

Fig. 10 Rear main seal identification stamping:

1983 & EARLY PRODUCTION 1984

1. Drain cooling and lubrication systems, then remove engine assembly.
2. Install engine in suitable engine stand in inverted position, then remove oil pan and oil pump.
3. Remove timing chain. Refer to ``Timing Chain, Replace'' for procedure.
4. Rotate crankshaft to horizontal position, then remove connecting rod bearing nuts, caps and bearings. Keep nuts, caps and bearings in order so they can be installed in their original positions.
5. Remove main bearing bolts, caps and bearings, then the crankshaft. Keep bolts, caps and bearings in order so they can be installed in their original positions.
6. Remove old seal and sealant from cylinder block grooves and rear main cap grooves.
7. Clean excess sealant from crankshaft using suitable solvent.
8. Apply a light coating of sealant 1052357 or equivalent to outside diameter of seal included in kit 14081761.
9. Place seal tool assembly on rear area of crankshaft, then position tool so arrow points towards cylinders and crankcase, Fig. 10.
10. Install crankshaft in engine with tool installed, then remove tool and discard.
11. Lightly lubricate crankshaft journals.
12. Seal rear main bearing split-line surface with sealant 1052357 or equivalent, then install rear main bearing and cap.
13. Install remaining main bearings, caps and bolts. Torque to specifications.
14. Install connecting rod bearings, caps and bolts. Torque to specifications.
15. Install oil pump.
16. Install timing chain.
17. Install oil pan, then the engine assembly.