Chevrolet Chevette/1000 1976-1988 Repair Guide

Pistons and Connecting Rods (Diesel Engine)

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REMOVAL





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Fig. Fig. 1Exploded view of the piston and connecting rod assembly for a diesel engine



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Fig. Fig. 2Piston disassembly for diesel engines

  1. Remove the engine assembly as outlined earlier in this section.
  2.  
  3. Remove the timing belt.
  4.  
  5. Remove the cam cover.
  6.  
  7. Remove the rocker arm assembly.
  8.  
  9. Remove the camshaft.
  10.  
  11. Remove the cylinder head assembly.
  12.  
  13. Remove the oil pan.
  14.  
  15. Remove the carbon deposits from the upper part of the cylinder wall (cylinders to be serviced) with a scraper.
  16.  
  17. Remove the connecting rod cap nuts and remove the bearing and cap.
  18.  
  19. Remove the piston and connecting rod by pushing on the edge of the connecting rod with a hammer handle or piece of wood.
  20.  

Refer to the piston disassembly illustration for removal of the piston pin and rings.

INSPECTION



Pistons


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Fig. Fig. 3Measure piston diameter with an outside micrometer

  1. Check the pistons for scuffs, cracking or wear. Replace the pistons with new ones if found to be defective.
  2.  
  3. Measure the clearance between the pistons and cylinder walls as follows:
  4.  
    1. With an outside micrometer, measure the diameter of the piston at a point below the piston head (grading position) in direction at a right angle to the piston pin. Standard is 63.7mm.
    2.  
    3. With a cylinder bore indicator, measure the cylinder bore diameter at the lower section where the amount of wear is smallest. Compare the value obtained with the cylinder bore diameter to determine the clearance. If the amount of clearance deviates from 0.005-0.045mm, replace the pistons with new ones.
    4.  


Piston Pins


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Fig. Fig. 4Measuring the piston pin outside diameter



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Fig. Fig. 5Measure the clearance between the piston pin and hole and compare with specifications

Visually inspect for damage, wear or other abnormal conditions. Measure the diameter at several points around the circumference, then check the clearance between the piston pin and piston pin hole.

Pin outside diameter:



Standard-25.0mm
 
Limit-24.97mm
 

Piston pin and hole:



Standard-0.002-0.012mm
 
Limit-0.05mm
 

Piston Rings


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Fig. Fig. 6Measure the piston ring gap



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Fig. Fig. 7Measure the piston ring and ring groove

The piston rings should be replaced with new ones whenever the engine is overhauled or if found to be worn or damaged.

  1. Insert the piston rings into the cylinder bore and push them down to the skirt (portion where bore diameter is smallest) using the piston head. This will position piston rings at a right angle to the cylinder wall. Measure the ring gap with a feeler gauge. Replace the piston rings with new ones if the measured value is beyond the limit shown in the chart.
  2.  
  3. With a feeler gauge, measure the clearance between the piston ring and ring grooves in the piston at several points around the circumference of the piston. Replace the piston rings together with the piston if the measured value is greater than 0.15mm or if abnormal contact is noticeable on the upper or lower face of the piston rings.
  4.  

Refer to the Piston and Ring Specifications Chart at the beginning of this section.

Connecting Rods


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Fig. Fig. 8Location of the piston and connecting rod marks

If distortion of connecting rod is suspicious, remove piston from the connecting rod and check for parallelism. Check the connecting rods for distortion and bending by installing on a connecting rod alignment tool. Correct or replace the connecting rod if the amount of distortion is greater than 0.2mm or bending is greater than 0.15mm per 100mm of length.

Bushing Replacement


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Fig. Fig. 9Measuring the bushing and pin clearance



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Fig. Fig. 10Bushing replacement on a diesel engine

Measure the inside diameter of the connecting rod,small end bushing and outside diameter of the piston pin clearance between bushing and piston pin 0.05mm

  1. Remove and install bushing using remover/installer J-29765 as shown. Align the bushing hole with the connecting rod oil hole.
  2.  
  3. After installing a new bushing, finish the bushing bore with a pin hole grinder.
  4.  

ASSEMBLY





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Fig. Fig. 11Use a suitable pair of pliers to install the snapring



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Fig. Fig. 12Installing the piston rings



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Fig. Fig. 13View of the oil ring installation. The ends of the coil expander should be opposed to the ring gap



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Fig. Fig. 14Ring gap locations on diesel engines

  1. Install the piston on the connecting rod, so that combustion chamber on piston head is on the same side with the cylinder number mark side (side with bearing stopper) of the connecting rod big end. Mark on the connecting rod should be on the same side of the front mark on the piston.
  2.  
  3. Apply engine oil to the piston pin and install it into the piston pin hole in the piston using finger pressure.
  4.  
  5. Install the snaprings into slots in piston pin hole properly.
  6.  
  7. Install the piston rings in sequence of coil expander, oil ring, 2nd compression ring and 1st compression ring.
  8.  
  9. Install the 1st and 2nd compression rings and oil ring with the N mark facing upward. The ends of the coil expander should be opposed to the oil ring gap.
  10.  

After installation of piston rings, apply engine oil to the circumference of the rings and check that each ring rotates smoothly.

INSTALLATION





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Fig. Fig. 15Rod bearing installation



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Fig. Fig. 16Use a suitable installation tool to push the piston (notched mark to the front of the engine) into the cylinder



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Fig. Fig. 17Install the bearing caps and tighten to specifications

  1. Apply clean engine oil to bearing surfaces, outer edge of piston and rings. Be sure rod bearing projected portions are fitted to the recess in the rod and cap.
  2.  
  3. The position ring gaps should be set in piston is 180 degrees apart.
  4.  
  5. Using a piston installer, push piston (with its notched mark to front of engine) into the cylinder until the connecting rod is brought into contact with the crank pin. Use a piece of wood or hammer handle to push piston into bore (Piston Installer J-8037).
  6.  
  7. Install the connecting rod bearing cap by aligning it with the cylinder number mark on the connecting rod.
  8.  
  9. Apply engine oil to the threads and seating face of the nuts, then install and tighten the nuts to 88 Nm (65 ft. lbs.).
  10.  
  11. Check that crankshaft turns smoothly.
  12.  
  13. The remainder of the installation is the reverse of removal.
  14.  

 
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