GM 12598610 Engine Crankshaft

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The crankshaft can only be removed when the engine is detached from the car, on condition that the following parts have been already unbolted, flywheel, crankshaft pulley, timing chain, oil pan, oil pump body, oil filter, piston/connecting rod assemblies. Before taking out the crankshaft, loosen the bearing cap and use dial indicator to measure crankshaft end play. Loosen the crankshaft and align the indicator pin with the crankshaft centerline, and swing the crank to the other side of the centreline to check zero on the machine indicator which should ideally range between 0.003 to 0.010 inch (0.076 to 0.254 mm). In case a dial indicator is not easily accessible one can use feeler gauges to get the clearance. Loosen the main bearing cap bolts and then carefully take off the main bearing caps with the special attention to not to drop its bearing inserts. Carefully raise the crankshaft out of the engine, which could be a two-man job because of its great mass. For installation it is recommended to clean the engine block and crankshaft and ensure they are inspected. Place the engine block inverted, for example, on two struts, temporarily remove some of the recoil devices, and wash the bearing surfaces. Replace upper main bearing inserts in the engine block, has to match oil holes and put in lower inserts on main bearing caps. Wash off sticky-body material from the crankshaft and if possible, check the oil hole for dirt before placing it in position. Next, to determine the condition and oil clearance of the main bearing take off the plastic spacer and use Plastigage to check the position of that spacer without disturbing the oil clearance. If, after measuring, the clearance is not right, first, check that there was no debris present during the measurement and, if necessary, replace the bearing inserts. There should be no residue of Plastigage left on the shafts, if so remove it very gently. Finally for installation make sure the bearing insert faces are clean, then apply very thin coat of grease or assembly lube and then place the crankshaft back in its position. Place the main bearing caps in the right manner and smeared oil on the bolt threads and tightened according to the sequence. If not, recheck on crankshaft end play and turning it to and fro to ensure that it has smooth running with least resistance. Last but not least fit a new rear main oil seal.