Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Pistons and Connecting Rods

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REMOVAL



See Figures 1, 2, 3, 4, 5 and 6



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Fig. Fig. 1: Cover the rod studs with lengths of vacuum hose or rubber tubing to protect the crankshaft and cylinder walls during piston removal and installation



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Fig. Fig. 2: A ridge is created at the top of the cylinder during normal wear. The ridge MUST be removed before the pistons are extracted or damage will occur



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Fig. Fig. 3: Driving the piston out of the block using the wooden handle of a hammer



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Fig. Fig. 4: Place rubber hose over the connecting rod studs to protect the crankshaft and cylinder walls



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Fig. Fig. 5: Carefully tap the piston out of the bore using a wooden dowel



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Fig. Fig. 6: The notch on the side of the rod and bearing cap matches the groove on the bearing insert

It is recommended that the engine be removed from the vehicle and mounted on an engine stand, before removing the pistons and connecting rods from the engine.

  1. Refer to the Cylinder Head Removal and Installation procedures in this section, and remove the cylinder head.
  2.  

A ridge reamer is necessary for this operation. Place the piston at the bottom of its stroke, and cover it with a rag. Cut the ridge away with the ridge reamer, using extreme care to avoid cutting too deeply. Remove the rag, and remove the cuttings that remain on the piston with a magnet and a rag soaked in clean oil. Make sure the piston top and cylinder bore are absolutely clean before moving the piston. For more details, refer to the ridge removal and honing procedures later in this section.

  1. Drain the lubricant from the engine. Invert the engine on the stand, then remove the oil pan, the oil strainer and the pickup tube.
  2.  


CAUTION
The EPA warns that prolonged contact with used engine oil may cause a number of skin disorders, including cancer! You should make every effort to minimize your exposure to used engine oil. Protective gloves should be worn when changing the oil. Wash your hands and any other exposed skin areas as soon as possible after exposure to used engine oil. Soap and water, or waterless hand cleaner should be used.

  1. Position the piston to be removed at the bottom of its stroke, so that the connecting rod bearing cap can be easily reached.
  2.  
  3. Remove the connecting rod bearing cap nuts and the cap and the lower half of the bearing. Cover the rod bolts with lengths of rubber tubing or hose to protect the cylinder walls when the rod and piston assembly is driven out.
  4.  
  5. Push the piston/connecting rod assembly, out through the top of the cylinder block with a length of wood or a wooden hammer handle.
  6.  

When removing the piston/connecting rod assembly, be careful not to scratch the cylinder wall with the connecting rod.

RIDGE REMOVAL AND HONING



See Figures 7 and 8



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Fig. Fig. 7: Removing cylinder glazing using a flexible hone



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Fig. Fig. 8: Cylinder bore cross-hatch pattern

  1. Before the piston is removed from the cylinder, check for a ridge at the top of the cylinder bore. This ridge occurs because the piston ring does not travel all the way to the top of the bore, thereby leaving an unworn portion of the bore.
  2.  
  3. Clean away any carbon buildup at the top of the cylinder with sand paper, in order to see the extent of the ridge more clearly. If the ridge is slight, it will be safe to remove the pistons without damaging the rings or piston ring lands. If the ridge is severe, and easily catches your fingernail, it will have to be removed using a ridge reamer.
  4.  

A severe ridge is an indication of excessive bore wear. Before removing the piston, check the cylinder bore diameter with a bore gauge, as explained in the cleaning and inspection procedure. Compare your measurement with engine specification. If the bore is excessively worn, the cylinder will have to bored oversize and the piston and rings replaced.

  1. Install the ridge removal tool in the top of the cylinder bore. Carefully follow the manufacturers instructions for operation. Only remove the amount of material necessary to remove the ridge. Place the piston at the bottom of its stroke, and cover it with a rag. Cut the ridge away with the ridge reamer, using extreme care to avoid cutting too deeply. Remove the rag, and remove the cuttings that remain on the piston with a magnet and a rag soaked in clean oil. Make sure the piston top and cylinder bore are absolutely clean before moving the piston.
  2.  


WARNING
Be very careful if you are unfamiliar with operating a ridge reamer. It is very easy to remove more cylinder bore material than you want, possibly requiring a cylinder overbore and piston replacement that may not have been necessary.

  1. After the piston and connecting rod assembly have been removed, check the clearances as explained earlier in this section under the cleaning and inspection procedure, to determine whether boring and honing or just light honing are required. If boring is necessary, consult an automotive machine shop. If light honing is all that is necessary, proceed with the next step.
  2.  
  3. Honing is best done with the crankshaft removed, to prevent damage to the crankshaft and to make post-honing cleaning easier, as the honing process will scatter metal particles. However, if you do not want to remove the crankshaft, position the connecting rod journal for the cylinder being honed as far away from the bottom of the cylinder bore as possible, and wrap a shop cloth around the journal.
  4.  
  5. Honing can be done either with a flexible glaze breaker type hone or with a rigid hone that has honing stones and guide shoes. The flexible hone removes the least amount of metal, and is especially recommended if your piston-to-cylinder bore clearance is on the loose side. The flexible hone is useful to provide a finish on which the new piston rings will seat. A rigid hone will remove more material than the flexible hone and requires more operator skill.
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  7. Regardless of which type of hone you use, carefully follow the manufacturers instructions for operation.
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  9. The hone should be moved up and down the bore at sufficient speed to obtain a uniform finish. A rigid hone will provide a definite cross-hatch finish; operate the rigid hone at a speed to obtain a 45-65 degree (for all engines except the 2.2L gasoline) or a 45 degree (for the 2.2L gasoline engine) included angle in the cross-hatch. The finish marks should be clean but not sharp, free from embedded particles and torn or folded metal.
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  11. Periodically during the honing procedure, thoroughly clean the cylinder bore and check the piston-to-bore clearance with the piston for that cylinder.
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  13. After honing is completed, thoroughly wash the cylinder bores and the rest of the engine with hot water and detergent. Scrub the bores well with a stiff bristle brush and rinse thoroughly with hot water. Thorough cleaning is essential, for if any abrasive material is left in the cylinder bore, it will rapidly wear the new rings and the cylinder bore. If any abrasive material is left in the rest of the engine, it will be picked up by the oil and carried throughout the engine, damaging bearings and other parts.
  14.  
  15. After the bores are cleaned, wipe them down with a clean cloth coated with light engine oil, to keep them from rusting.
  16.  

CLEANING AND INSPECTION



Pistons

See Figures 9, 10, 11 and 12



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Fig. Fig. 9: Using a ring groove cleaner tool to properly clean the ring grooves



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Fig. Fig. 10: Use a ring expander tool to remove the piston rings



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Fig. Fig. 11: Clean the piston grooves using a ring groove cleaner



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Fig. Fig. 12: You can use a piece of old piston ring to clean the groove. Be careful, the rings are sharp

A piston ring expander is necessary for removing piston rings without damaging them; any other method (screwdriver blades, pliers, etc.) usually results in the ring being bent, scratched or distorted, or the piston itself being damaged. When the rings are removed, clean the piston grooves using an appropriate ring groove cleaning tool, using care not to cut too deeply. Thoroughly clean all carbon and varnish from the piston with solvent.


WARNING
Do not use a wire brush or caustic solvent (acids, etc.) on piston. Inspect the pistons for scuffing, scoring, cranks, pitting, or excessive ring groove wear. If these are evident, the piston must be replaced.

Clean the varnish from the piston skirts and pins with a cleaning solvent. DO NOT WIRE BRUSH ANY PART OF THE PISTON. Clean the ring grooves with a groove cleaner and make sure that the oil ring holes and slots are clean.

Inspect the piston for cracked ring lands, scuffed or damaged skirts, eroded areas at the top of the piston. Replace the pistons that are damaged or show signs of excessive wear.

Inspect the grooves for nicks of burrs that might cause the rings to hang up.

Measure the piston in relation to cylinder diameter. Refer to the cylinder bore cleaning and inspection procedures later in this section.

MEASURING THE OLD PISTONS

See Figures 13 and 14



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Fig. Fig. 13: Measure each piston's diameter in several locations using a micrometer

Check used piston-to-cylinder bore clearance as follows:

  1. Measure the cylinder bore diameter with a telescope gauge.
  2.  
  3. Measure the piston diameter. When measuring the pistons for size or taper, measurements must be made with the piston pin removed.
  4.  
  5. Subtract the piston diameter from the cylinder bore diameter to determine piston-to-bore clearance.
  6.  
  7. Compare the piston-to-bore clearances obtained with those clearances recommended in the "Piston and Connecting Rod'' chart in the beginning of this section. Determine if the piston-to-bore clearance is in the acceptable range.
  8.  
  9. When measuring taper, the largest reading must be at the bottom of the skirt.
  10.  
  11. If the measurement is not within specifications, the cylinders should be bored and new oversize pistons should be installed.
  12.  

SELECTING NEW PISTONS
  1. If the used piston is not acceptable, check the service piston size and determine if a new piston can be selected. Service pistons are available in standard, high limit and standard 0.254mm (0.010 in.) oversize.
  2.  
  3. If the cylinder bore must be reconditioned, measure the new piston diameter, then hone the cylinder bore to obtain the preferred clearance.
  4.  
  5. Select a new piston and mark the piston to identify the cylinder for which it was fitted. (On some cars, oversize pistons may be found. These pistons will be 0.010 in./0.254mm oversize.) Aftermarket piston manufacturers supply oversized pistons 0.030 in., 0.040 in., and 0.060 in. in most cases.
  6.  
  7. After the cylinder has been reconditioned and new pistons purchased, remeasure bore and piston to ensure proper piston fit.
  8.  

Connecting Rods

Wash the connecting rods in cleaning solvent and dry with compressed air. Check for twisted or bent rods and inspect for nicks or cracks. Replace the connecting rods that are damaged.

It is not advisable to remove the piston from the connecting rod unless part replacement is necessary. Whenever a piston is removed, the piston pin should be replaced. When examining a piston, look for scuffs, cracking or wear. Before removal of connecting rod(s) and cap(s), mark them with their respective cylinder number. This will insure a proper match during reinstallation.

Cylinder Bores

See Figure 14



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Fig. Fig. 14: A telescoping gauge may be used to measure the cylinder bore diameter

The piston should also be checked in relation to the cylinder diameter. Using a telescoping gauge and micrometer, or a dial gauge, measure the cylinder bore diameter perpendicular (90 degrees) to the piston pin, about 1-2 1 / 2 in. below the cylinder block deck (surface where the block mates with the heads). Then, with the micrometer, measure the piston perpendicular to its wrist pin on the skirt. The difference between the two measurements is the piston clearance.

If the clearance is within specifications or slightly below (after the cylinders have been bored or honed), finish honing is all that is necessary, If the clearance is excessive, try to obtain a slightly larger piston to bring the clearance within specifications. If this is not possible obtain, the first oversize piston and hone the cylinder or (if necessary) bore the cylinder to size. Generally, if the cylinder bore is tapered more than 0.005 in. (0.127mm) or is out-of-round more than 0.003 in. (0.0762mm), it is advisable to rebore for the smallest possible oversize piston and rings. After measuring, mark the pistons with a felt-tip pen for reference and for assembly.

Boring of the cylinder block should be performed by a reputable machine shop with the proper equipment. In some cases, clean-up honing can be done with the cylinder block in the vehicle, but most excessive honing and all cylinder boring MUST BE done with the block stripped and removed from the vehicle.

IDENTIFICATION AND POSITIONING



See Figures 15, 16, 17 and 18



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Fig. Fig. 15: Piston alignment-E-Series engine



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Fig. Fig. 16: Piston and connecting rod positioning-GA16i, CA16DE, CA18DE, GA16DE and SR20DE engines



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Fig. Fig. 17: Piston and rod alignment-CA16DE and CA18DE engines



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Fig. Fig. 18: Piston and rod alignment-CD17 diesel engine

The pistons are marked with a notch or a number stamped on the piston head. When installed in the engine the notch or number markings must be facing the front of the engine.

The connecting rods are installed in the engine with the oil hole facing the right side of the engine.

It is advisable to number the pistons, connecting rods and bearing caps in some manner so that they can be reinstalled in the same cylinder, facing in the same direction from which they are removed.

PISTON PIN REPLACEMENT



See Figure 19



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Fig. Fig. 19: Piston pin installation

Most engines covered by this information utilize a piston and pin assembly which are pressed together. Disassembly will require an arbor press, a suitable support and the proper drivers. It would be advised to have pistons replaced by a machine shop that can check the connecting rods, for twist and squareness. This pistons must be installed on the press exactly flat to keep from damaging the pistons or bending the rods.


WARNING
Do not use a wire brush or caustic solvent (acids, etc.) on pistons. Inspect the pistons for scuffing, scoring, cracks, pitting, or excessive ring groove wear. If these are evident, the piston must be replaced.

The piston pin, the piston and the connecting rod are held together as an assembly, by pressing piston pin into the connecting rod. An arbor press and a special pin removing stand tool No. KV10107400 or equivalent are used for removing and installing the piston pin.

PISTON RING REPLACEMENT



See Figures 20, 21, 22, 23 and 24



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Fig. Fig. 20: Piston ring identification and positioning



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Fig. Fig. 21: Piston ring positioning-CD17 diesel engine



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Fig. Fig. 22: Piston ring positioning-E-Series engine



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Fig. Fig. 23: Piston ring positioning-Gasoline engines except E-Series



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Fig. Fig. 24: Using a piston ring expander to install piston rings

Piston Ring End-Gap

See Figure 25



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Fig. Fig. 25: Measure the piston-to-bore clearance and piston ring end-gap

Piston ring end-gap should be checked while the rings are removed from the pistons. Incorrect end gap indicates the wrong size rings are being used; ring breakage could occur and engine damage could result.

Squirt clean engine oil into the cylinder, then carefully compress and insert the piston rings to be used in a cylinder, one at a time, into that cylinder. Position the rings approximately 1 in. (25mm) below the deck of the block at a point where bore diameter is smallest. The ring can be carefully positioned using the top of the piston, this will assure that the ring is properly squared to the cylinder walls. Measure the ring end-gap with a feeler gauge, and compare to the piston and ring chart earlier in this section. Carefully pull the ring out of the cylinder and, if a larger clearance is necessary, file the ends squarely with a fine file to obtain the proper clearance.

Piston Ring Side Clearance Check

See Figures 26 and 27



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Fig. Fig. 26: Measuring piston ring side clearance



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Fig. Fig. 27: Measuring the piston ring-to-ring groove clearance

Check the pistons to see that the ring grooves and oil return holes have been properly cleaned. Slide a piston ring into its groove, and check the side clearance with a feeler gauge. On used pistons, make sure you insert the gauge between the ring and its lower land (lower edge of the groove), because any wear that occurs forms a step at the inner portion of the lower land. If the piston grooves have worn to the extent that relatively high steps exist on the lower land, the piston should be replaced, because these will interfere with the operation of the new rings and ring clearance will be excessive. Piston rings are not furnished in oversize widths to compensate for ring groove wear.

Ring Installation

See Figures 28, 29, 30 and 31



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Fig. Fig. 28: Piston ring installation-except SR20DE engine



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Fig. Fig. 29: Piston ring installation- SR20DE engine



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Fig. Fig. 30: Use a piston ring expander to install the compression rings, starting from the bottom



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Fig. Fig. 31: Most rings are marked to show which side should face upward

Install the rings on the piston, lowest ring first, using a piston ring expander. There is a high risk of breaking or distorting the rings, or scratching the piston, if the rings are installed by hand or other means. Depending on the design, bottom ring or oil control ring is provided in several pieces and assembled on the piston. The oil control ring may not require the use of a ring expander, but great care must be used to avoid damage to the ring and piston.

Position the rings on the piston so the ring gaps do not line up. The spacing of the various piston ring gaps is crucial to proper oil retention and even cylinder wear. When installing new rings, refer to the installation diagram furnished with the new parts.

ROD BEARING REPLACEMENT



See Figures 32, 33, 34 and 35



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Fig. Fig. 32: Checking the connecting rod bearing with Plastigage®



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Fig. Fig. 33: Checking the connecting rod bearing side clearance



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Fig. Fig. 34: Aligning the bearing's oil hole with the hole in the connecting rod



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Fig. Fig. 35: After the cap is removed again, use the scale supplied with gauge material to check clearances

The connecting rod side clearance and the big-end bearing inspection should be performed while the rods are still installed in the engine. Determine the clearance between the connecting rod sides and the crankshaft, using a feeler gauge. If the side clearance is below the minimum tolerance- 0.0040-0.0197 in. (0.10-0.50mm) -have a machine shop correct the tolerance; if the clearance is excessive, substitute an unworn rod and recheck the clearance.

To check the connecting rod big-end bearing clearances, remove the rod bearing caps one at a time. Using a clean, dry shop rag, thoroughly clean all of the oil from the crank journal and the bearing insert in the cap.

The Plastigage® gauging material you will be using to check the clearances with, is soluble in oil; therefore any oil on the journal or bearing could result in an incorrect reading.

Lay a strip of Plastigage® across the bearing insert. Reinsert the bearing cap and retorque to specifications.

Remove the rod cap and determine the bearing clearance by comparing the width of the now flattened Plastigage® to the scale on the Plastigage® envelope. The journal taper is determined by comparing the width of the strip near its ends. Rotate the crankshaft 90° and retest, to determine the journal eccentricity.

DO NOT rotate the crankshaft with Plastigage® installed, for an incorrect reading will result.

If the clearances are not within the tolerances, the bearing inserts must be replaced with ones of the correct oversize or undersize and/or the crankshaft must be ground. If installing new bearing inserts, make sure that the tabs fit correctly into the notch of the bearing cap and rod. Lubricate the face of each insert before installing them onto the crankshaft.

Install the upper connecting rod bearing with its oil hole aligned with the hole in the connecting rod. Align the bearing wedge with the cutout in the notch in the connecting rod. Make sure all dirt and carbon is removed from the bearing bore before installing.

INSTALLATION



See Figures 36, 37, 38 and 39



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Fig. Fig. 36: Using a ring expander install the rings onto the pistons



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Fig. Fig. 37: Lubricate the components, compress the rings and gently drive the piston into the bore



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Fig. Fig. 38: Pistons are usually marked to indicate which side faces front



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Fig. Fig. 39: Installing the piston into the block using a ring compressor and the handle of a hammer

  1. Keep all of the components from each cylinder together and install them in the cylinder from which they were removed.
  2.  
  3. Lubricate all of the piston/connecting rod components with engine oil, including the bearing face of the connecting rod and the outer face of the pistons with engine oil.
  4.  

See the illustrations for the correct positioning of the piston rings.

  1. Turn the crankshaft until the rod journal of the particular cylinder you are working on is brought to the TDC position.
  2.  
  3. Clamp the piston/ring assembly into a ring compressor, the notched mark or number (on the piston head) must face the front of the engine and the oil hole (on the side of the connecting rod) must face the right side of the engine; push the piston/connecting rod assembly into the cylinder bore until the big bearing end of the connecting rod seats on the rod journal of the crankshaft.
  4.  

Use care not to scratch the cylinder wall with the connecting rod.

  1. Push down on the piston/connecting rod assembly, while turning the crankshaft (the connecting rod rides around on the crankshaft rod journal), until the crankshaft rod journal is at Bottom Dead Center (BDC).
  2.  
  3. Align the mark on the connecting rod bearing cap with that on the connecting rod and torque the connecting rod bearing cap bolts to 24-27 ft. lbs. (33-37 Nm).
  4.  
  5. Install the oil strainer, pickup tube and oil pan.
  6.  
  7. Install the cylinder head.
  8.  
  9. Install engine assembly in vehicle.
  10.  
  11. Check all fluid levels and road test.
  12.  

 
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