Nissan 12201-21V80 Crankshaft Assembly

Remove the oil pan, followed by the pick-up tube and oil pump. Next, take out the connecting rods and pistons, then remove the four oil seal retainer bolts. Pull the oil seal retainer from the retaining pins to detach it. Loosen each of the main bearing cap assembly retaining bolts a quarter turn at a time, in the correct numerical order, until they can be removed by hand. Ensure the main bearing cap assembly is marked with an arrow pointing to the front of the engine; if not, mark it accordingly to ensure proper reinstallation. Gently tap the cap assembly with a soft face hammer to separate it from the engine block, using the main bearing cap bolts as levers if necessary, and take care not to drop the bearing inserts. Finally, carefully lift the crankshaft out of the engine, ideally with assistance due to its weight, and with the bearing inserts in place, return the cap assembly to the engine block and tighten the bolts finger tight.

Remove all burrs from the crankshaft oil holes using a stone, file, or scraper to ensure sharp edges do not gouge or scratch the new bearings. Clean the crankshaft with solvent and dry it with compressed air, ensuring the oil holes are cleaned with a stiff brush and flushed with solvent. Check the main and connecting rod bearing journals for uneven wear, scoring, pits, and cracks, and inspect the rest of the crankshaft for cracks and other damage, which should be magnafluxed by an automotive machine shop to reveal hidden issues. Measure the diameter of the main and connecting rod journals with a micrometer at several points to detect taper and out-of-round conditions, comparing the results to the specified limits. If the journals are damaged, tapered, out-of-round, or worn beyond acceptable limits, have the crankshaft reground by an automotive machine shop, ensuring the correct size bearing inserts are used if reconditioned. Check the oil seal journals at each end of the crankshaft for wear and damage, as worn grooves or nicks may cause new seals to leak; an automotive machine shop may repair the journal with a thin sleeve, or a new crankshaft may be necessary if repair is not feasible. Finally, examine the main and rod bearing inserts.

Take measurements at each end of the journal, near the crank counterweights, to check for taper.

Remove all burrs from the crankshaft oil holes with a stone, file, or scraper.

Loosen the main bearing cap bolts 1/4 turn at a time each, until the bearing cap and brace assembly can be removed by hand. Loosen the bolts in the reverse of the tightening sequence.