Oldsmobile 12555637 Engine Crankshaft

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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.

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.

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.

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.

The engine should be positioned with the bottom facing up.

Finally, examine the main and rod bearing inserts.

Scrape off any Plastigage material without damaging the bearing faces, then lift the crankshaft out, clean the bearing faces in the block, and apply a thin layer of engine assembly lube.

After ensuring the engine block and crankshaft are clean, position the block with the bottom facing up, remove the main bearing cap assembly, and clean the bearing surfaces.

Remove the main bearing cap bolts and lift out the caps, laying them out in order for correct reinstallation.

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.

Examine the main and rod bearing inserts for further assessment.

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.

After removing the bolts and caps, compare the width of the crushed Plastigage to determine the oil clearance, ensuring it meets specifications.

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.

For V6 engines, tighten the bolts starting from the center main and working outward, seating the thrust bearings before torquing the rear main cap.