Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Crankshaft and Main Bearings

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REMOVAL & INSTALLATION



See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Crankshaft removal showing hose lengths over the studs and rubber bands holding the rods out of the way



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Fig. Fig. 2: Checking crankshaft thrust bearing clearance



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Fig. Fig. 3: Checking crankshaft end-play with a feeler gauge



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Fig. Fig. 4: Carefully pry the shaft back and forth while reading the gauge to check crankshaft end-play

Except E-Series, CA16DE and CA18DE Engines
  1. Disconnect the negative (-) battery cable.
  2.  
  3. Remove the engine from the vehicle and separate from the transaxle.
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  5. Place the engine in a suitable workstand.
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  7. Remove the flywheel or converter plate from the crankshaft.
  8.  
  9. Remove the front timing cover.
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  11. Remove the oil pan.
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  13. Remove the crankshaft bearing caps.
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  15. Remove the connecting rod bearing caps and place rubber hoses over the connecting rod bolts to protect the crankshaft journals.
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  17. Remove the rear seal carrier.
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  19. Push the connecting rods into the cylinder.
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  21. Carefully lift the crankshaft out of the engine, turning slightly to disengage the connecting rods.
  22.  

To install:
  1. Install the oil pan bolts adjacent to the connecting rods. Place rubber bands around the connecting rod bolt to hold the rod in place during crankshaft installation.
  2.  
  3. Lubricate all bearing surfaces with assembly lube. Make sure all bearings are in place before assembly.
  4.  
  5. Install the crankshaft with the help of an assistant.
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  7. Install the crankshaft bearing caps and torque to specifications.
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  9. Install the connecting rod bearing caps and torque to specifications.
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  11. Install the remaining components, install the engine and check for oil pressure.
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E-Series, CA16DE and CA18DE Engines
  1. Refer to the Piston and Connecting Rod Removal and Installation procedures in this section, and remove the connecting rod bearings from the crankshaft.
  2.  

It may not be necessary to remove the piston/connecting rod assemblies from the cylinder block.

  1. On the E-series engine, remove the jackshaft sprocket, the crankshaft sprocket, the front side rear timing plate, then the clutch/flywheel assembly (manual transaxle) or driveplate (automatic transaxle), the rear oil seal retainer and the rear plate. On the CA16DE and CA18DE engines, remove the water pump.
  2.  
  3. Check the crankshaft thrust clearance (end-play) before removing the crankshaft from the engine block. Using a prybar, pry the crankshaft forward to the extent of its travel and measure the clearance at the No. 3 main bearing. Pry the crankshaft rearward to the extent of its travel and measure the clearance on the other side of the bearing.
  4.  

If the clearance is greater than specified, the thrust bearing must be replaced. When removing the crankshaft bearing caps, be sure to keep the bearing together with the caps, unless new bearings are going to be installed.

  1. Remove the crankshaft bearing caps, the cap bearings and the crankshaft from the engine.
  2.  
  3. To install, check the clearances with the Plastigage® method, then replace the bearings if necessary. Torque the crankshaft bearing cap bolts to specifications.
  4.  
  5. Reassemble the engine.
  6.  

When torquing the main bearing caps, start with the center bearing and work towards both ends at the same time.

CLEANING AND INSPECTION



See Figures 5 and 6



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Fig. Fig. 5: Mount a dial gauge to read crankshaft run-out



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Fig. Fig. 6: Turn the crankshaft slowly by hand while checking the gauge

The crankshaft inspection and servicing should be handled exclusively by a reputable machinist, for most necessary procedures require a dial indicator, fixing jigs and a large micrometer; also machine tools, such as: crankshaft grinder. The crankshaft should be thoroughly cleaned (especially the oil passages), Magnafluxed (to check for cracks) and the following checks made: Main journal diameter, crank pin (connecting rod journal) diameter, taper, out-of-round and run-out. Wear beyond the specification limits, in any of these areas, means the crankshaft must be reground or replaced.

Crankshaft
  1. Clean the crankshaft with solvent and a brush. Clean the oil passages with a suitable brush, then blow them out with compressed air.
  2.  
  3. Inspect the crankshaft for obvious damage or wear. Check the main and connecting rod journals for cracks, scratches, grooves or scores. Inspect the crankshaft oil seal surface for nicks, sharp edges or burrs that could damage the oil seal or cause premature seal wear.
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  5. If the crankshaft passes a visual inspection, check journal run-out using a dial indicator. Support the crankshaft in V-blocks and check the run-out. Compare to specifications.
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  7. Measure the main and connecting rod journals for wear, out-of-roundness or taper, using a micrometer. Measure in at least 4 places around each journal and compare your findings with the journal diameter specifications.
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  9. If the crankshaft fails any inspection for wear or damage, it must be reground or replaced.
  10.  

Main Bearings

Like connecting rod big-end bearings, the crankshaft main bearings are shell-type inserts that do not utilize shims and cannot be adjusted. The bearings are available in various standard and undersizes; if main bearing clearance is found to be excessive, a new bearing (both upper and lower halves) is required.

Generally, the lower half of the bearing shell (except No. 1 bearing) shows greater wear and fatigue. If the lower half only shows the effects of normal wear (no heavy scoring or discoloration), it can usually be assumed that the upper half is also in good shape; conversely, if the lower half is heavily worn or damaged, both halves should be replaced. NEVER REPLACE ONE BEARING HALF WITHOUT REPLACING THE OTHER!

MAIN BEARING CLEARANCE CHECK AND REPLACEMENT



The following procedure requires the use of Plastigage® or a micrometer set consisting of inside and outside micrometers, and a dial indicator.

Checking the main bearing clearances is done in the same manner as checking the connecting rod big-end clearances.

  1. With the crankshaft installed, remove the main bearing cap. Clean all of the oil from the bearing insert (in the cap and the crankshaft journal), for the Plastigage® material is oil-soluble.
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  3. Lay a strip of Plastigage® across the full width of the bearing cap and install the bearing cap, then torque the cap to specifications.
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DO NOT rotate the crankshaft with the Plastigage® installed.

  1. Remove the bearing cap and compare the scale on the Plastigage® envelope with the flattened Plastigage® material in the bearing. The journal taper is determined by comparing the width of both ends of the Plastigage® material. Rotate the crankshaft 90° and retest, to determine eccentricity.
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  3. Repeat the procedure for the remaining bearings. If the bearing journal and insert appear to be in good shape (with no unusual wear visible) and are within tolerances, no further main bearing service is required. If unusual wear is evident and/or the clearances are outside specifications, the bearings must be replaced and the cause of their wear determined.
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