Oldsmobile 12555637 Engine Crankshaft

The crankshaft can only be removed after the engine has been taken out of the vehicle, assuming that the flywheel or driveplate, vibration damper/crankshaft pulley hub, timing chain (for V6 engines), oil pan, oil pump, and piston/connecting rod assemblies have been detached. For engines with a one-piece rear main oil seal, the seal housing must be unbolted from the block prior to crankshaft removal. First, check the end play by mounting a dial indicator aligned with the crankshaft and touching one of the crank throws. Push the crankshaft to the rear and zero the dial indicator, then pry it to the front and note the reading, which indicates the end play. If the end play exceeds specifications, inspect the thrust surfaces for wear; if no wear is found, new main bearings may resolve the issue. If a dial indicator is unavailable, feeler gauges can be used by prying the crankshaft to the front and measuring the clearance between the crankshaft and the thrust main bearing. Check the main bearing caps for markings indicating their locations, numbering them consecutively from front to rear if necessary, and loosen the bolts gradually until they can be removed by hand. Gently tap the caps with a soft-face hammer to separate them from the block, using the bolts as levers if needed, and take care not to drop the bearing inserts. Finally, lift the crankshaft out of the engine, ideally with assistance, and return the bearing inserts to their positions in the block and main bearing caps, tightening the bolts finger tight.

Using solvent clean the crankshaft and if possible air dry it, always ensure that the holes are brushed with stiff brush and flushed with solvent. Using a thread mike or feeler gauge, measure the journal diameters of all main and connecting rod bearings for amount of ovality or taper and look for signs of scoring, pits or cracks, etc. Examine the rest of the crankshaft for any cracks or other damage. Use a micrometer to take the actual measurements of the diameter of the main and connecting rod journals and compare the same with the standard dimensions where by taking measurements at different positions around the circumference of each journal in order to check for taper or being out of round. Further, also take measurements at each end of the journal, at a plane perpendicular to the crank throw to detect taper. If the journals are badly scored, undersized, oval or excessively worn, have the crankshaft reconditioned by an automotive machine shop and, if reconditioning is done, use the correct size bearing inserts. Last but not the least, check on the main and the rod bearing inserts.

Remove all burrs from the crankshaft oil holes with a stone, file, or scraper to ensure the oil holes are chamfered, preventing sharp edges from gouging or scratching the new bearings. Clean the crankshaft with solvent and dry it with compressed air if available, ensuring to clean the oil holes with a stiff brush and flush them 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. Using a micrometer, measure the diameter of the main and connecting rod journals at several points to detect taper and out-of-round conditions, taking measurements at each end of the journal near the crank throws. If the crankshaft journals are damaged, tapered, out-of-round, or worn beyond specified limits, have the crankshaft reground by an automotive machine shop, ensuring the use of the correct size bearing inserts if reconditioned. Check the oil seal journals at each end of the crankshaft for wear and damage; if grooves, nicks, or scratches are present, the new seal may leak upon reassembly. In some cases, an automotive machine shop may repair the journal by pressing on a thin sleeve, but if repair isn't feasible, a new or different crankshaft should be installed. Examine the main and rod bearing inserts for further assessment.

Remove all burrs from the crankshaft oil holes with a stone, file, or scraper to ensure the oil holes are chamfered, preventing sharp edges from gouging or scratching the new bearings. Clean the crankshaft with solvent and dry it with compressed air if available, ensuring to clean the oil holes with a stiff brush and flush them 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. Using a micrometer, measure the diameter of the main and connecting rod journals at several points to detect taper and out-of-round conditions, taking measurements at each end of the journal near the crank throws. If the crankshaft journals are damaged, tapered, out-of-round, or worn beyond specified limits, have the crankshaft reground by an automotive machine shop, ensuring the use of the correct size bearing inserts if reconditioned. Check the oil seal journals at each end of the crankshaft for wear and damage; if grooves, nicks, or scratches are present, the new seal may leak upon reassembly. In some cases, an automotive machine shop may repair the journal by pressing on a thin sleeve, but if repair isn't feasible, a new or different crankshaft should be installed. Examine the main and rod bearing inserts for further assessment.

Before removing the crankshaft, check the endplay by mounting a dial indicator with the stem aligned with the crankshaft and touching one of the crank throws. Push the crankshaft to the rear and zero the dial indicator, then pry it to the front as far as possible to check the reading; the distance moved indicates the endplay. If it exceeds the specified limit, inspect the crankshaft thrust surfaces for wear, and if no wear is found, replacing the main bearings should resolve the issue. If a dial indicator is unavailable, use feeler gauges by prying or pushing the crankshaft to the front and slipping the gauges between the crankshaft and the thrust main bearing to measure the clearance, which reflects the endplay. Loosen the main bearing cap bolts a quarter turn at a time until they can be removed by hand, checking for markings on the caps to identify their locations, usually numbered from the front to the rear; if unmarked, use stamping dies or a center-punch to label them. Most caps have a cast-in arrow indicating the front of the engine. Gently tap the caps with a soft-faced hammer to separate them from the engine block, using the bolts as levers if necessary, and take care not to drop the bearing insert if it comes out with the cap. Finally, lift the crankshaft out of the engine, ideally with assistance due to its weight, and with the bearing inserts in place, return the caps to their respective locations on the engine block and tighten the bolts finger tight.

The installation of a crankshaft can be one of the first steps to rebuild an engine, assuming that the crankshaft and engine block have been to a degree of degreasing, inspection and repair. Place the engine upside down and then go ahead and take out the main bearing cap screws and pull out the cap and lay it tactical for easiness of reassembly. In case the old bearing inserts are there, they should be taken out and the main bearing areas should be wiped using a piece of cloth free from any form of lint. New main bearing insert, backs need to be cleaned and one half is fitted into the respective main bearing saddle in the block and tabs and oil holes should align without the use of lubrication. The flanged thrust bearing is to be fitted in suitable cap and saddle according to the type of the engine. Scrub the bearing influences and crankshaft main bearing journals, ensure that the oil channels have dirt. After that, you should clean the crankshaft and, with great accuracy, install counterweights sideways in the main bearings. Examining and measuring Plastigage to control the main bearing oil clearance: Stip trimming Plastigage and installing the same on each crankshaft main bearing journal; it must be parallel to the crankshaft main bearing journal axis. Degrease the bearing faces of the caps and replace them in their original positions with the arrows facing forward then torque the main bearing cap bolts to 90lb.in in three levels without rotating the crankshaft. After loosening the bolts and the caps, check the width of the compressed Plastigage and guarantee that the oil clearance complies with the requirement of the standard. If the clearance is wrong it has to be checked if the size of the bearing inserts is increased by dirt or oil. Remove all the Plastigage material carefully not scratching the bearing faces, lift the crankshaft and also clean the block bearing faces and apply a coat of assembly lube. Install the crankshaft back, also lube the lower bearing halves, and put the caps in as the arrows will indicate forward. For the V6 engines, first center main has to be tightened and then the thrust bearings have to be seated after then rear main cap is to be torqued. On four cylinders engines, torquing must include tightening of all bearing caps to a finger tight stage, setting of thrust bearings then tightening of all bearing caps to the standard torque settings. Turn the crankshaft with your hand and do some check and turn the crankshaft horizontally and do some check and at last perform check of end play of the crankshaft using feeler gauge or dial gauge.

Clean the bearing faces and crankshaft main bearing journals, checking for dirt in the oil holes.

After cleaning the crankshaft, lay it in the block and check the main bearing oil clearance using Plastigage. Install the main bearing caps without disturbing the Plastigage, then tighten the bolts according to the specified sequence.

Recheck the crankshaft endplay and rotate the crankshaft by hand to check for any binding.

Mount a dial indicator and touch the end of the crankshaft. Pry the crankshaft to the rear and zero the dial indicator, then pry it to the front and check the reading.