Connecting Rod: Service and Repair
Piston and Connecting Rod
Disassembly
1. Remove cylinder head assembly (1).
2. Remove cylinder head gasket (2).
3. Remove oil pan assembly and oil pan support (3).
4. Remove oil strainer.
5. Remove balance unit assembly.
6. Remove connecting rod cap with connecting rod lower.
7. Remove piston and connecting rod assembly (7).
Note: Before removing piston and connecting rod assembly, measure thrust clearance.
^ Remove any ridge or carbon build up from the top end of the cylinder.
8. Remove the piston rings (8) with a piston ring expander. Arrange the removed piston rings in the cylinder number order.
9. Remove the piston pin (9).
^ Heat the connecting rod and the piston pin with oil heater, when it temperature is keep at 280° C - 320° C.
^ Push the piston pin with brass bar.
Note: Keep the parts removed from each cylinder separate. All parts must be reinstalled in their original positions.
10. Piston (10).
11. Connecting rod (11).
Inspection and Repair
Pistons (10)
Carefully clean away all the carbon adhering to the piston head and the piston ring grooves.
Note: Never use a wire brush to clean the pistons. Damage will result. Visually check each piston for cracking, scoring, and other signs of excessive wear. If any of the above conditions are found, the piston must be replaced.
Piston Rings (8)
Any worn or damaged part discovered during engine overhaul must be replaced with a new one.
1. Ring end gap measurement.
^ Insert the piston ring into the bore.
^ Push the ring by the piston, at a right angle to the wall, into the point at which the cylinder bore diameter is the smallest.
^ Measure the ring end gap.
2. Measure the clearance between the piston ring groove and the piston ring with a feeler gauge. If the piston ring groove / piston ring clearance exceeds the specified limit, the piston must be replaced.
Compression Ring Clearance
Standard: 0.02 mm - 0.04 mm (0.0008 inch - 0.0016 inch)
Piston Pin (9)
Note: Do not reuse the old piston pin.
1. Use a micrometer to measure the new piston pin outside diameter in both directions at three different positions.
2. Measure the inside diameter of the connecting rod small end. If the fitting interference between the small end and pin does not conform to the specified value, the connecting rod must be replaced.
Standard: 0.02 mm - 0.041 mm (0.0008 inch - 0.0016 inch)
3. Insert the new pin into the piston and rotate it. If the pin rotates smoothly with no backlash, the clearance is normal. If there is backlash or roughness, measure the clearance. If the clearance exceeds the specified limit, the piston must be replaced.
Clearance
Standard: 0.011 mm - 0.014 mm (0.0004 inch - 0.0005 inch)
Connecting Rods (11)
1. Measure the oil clearance between the connecting rod and the crankshaft.
1. Remove the connecting rod cap nuts and the rod caps (12).
Arrange the removed rod caps in the cylinder number order.
2. Clean the rod bearings and the crankshaft pins.
3. Carefully check the rod bearings. If even one bearing is found to be damaged or badly worn, the entire bearing assembly must be replaced as a set. Reinstall the bearings in their original positions. Apply plastigage to the crank pin.
4. Reinstall the rod caps (12) to their original positions.
Tighten the rod cap nuts.
1st step: 35 Nm (26 ft. lbs.)
2nd step: 45°
3rd step: 15°
Note: Do not allow the crankshaft to rotate.
5. Remove the rod caps.
6. Measure the width of the plastigage and determine the oil clearance. If the oil clearance exceeds the limit, replace the rod bearing as a set.
Standard: 0.006 mm - 0.031 mm (0.0002 inch - 0.0012 inch)
Limit: 0.12 mm (0.0047 inch)
7. Clean the plastigage from the bearings and the crankshaft pins.
Reassembly
1. Install connecting rod
2. Install piston
3. Install piston pin
- Apply a thin coat of engine oil to the piston pin. Try to insert the piston pin into the piston pin hole with normal finger pressure.
Note: When changing piston/connecting rod combinations, do not change the piston/piston pin combination and do not reuse the old piston pin.
- Attach the piston to the connecting rod with the piston front mark and the connecting rod front mark on the same side.
- Heat the connecting rod small end to a suitable temperature to ensure smooth installation.
4. Install piston ring with the piston ring expander.
^ New piston rings with "top" uppermost - use commercially available pliers.
^ Position ring gaps:
1. Compression rings 1800 to each other as illustrated.
2. Offset oil control rings 25 to 50 mm/1 to 2 inch from gap of second compression ring.
^ After installation, apply engine oil to the entire circumference of the piston rings. Check to see that all the rings rotate smoothly.
5. Install piston and connecting rod assembly.
^ Insert the bearings into the connecting rods and caps. Apply new engine oil to the bearing faces and nuts.
^ Tighten the connecting rod cap nuts in 3 steps:
1st step: 35 Nm (26 ft. lbs.)
2nd step: 45°
3rd step: 15°
Note: Do not apply engine oil to the bearing back faces.
6. Install the oil gallery.
7. Install the oil strainer and O-ring.
8. Install balance unit assembly. Refer to Balance Unit Assembly.
9. Install oil pan support assembly.
10. Install cylinder head gasket.
11. Install cylinder head assembly.