Piston and Connecting Rod
Components and Component Location
Components
| 1. Piston ring 2. Snap ring 3. Piston pin 4. Piston |
5. Connecting rod 6. Upper connecting rod bearing 7. Lower connecting rod bearing 8. Connecting rod bearing cap |
Repair Procedures
Disassembly
Engine removal is required for this procedure.
Remove the engine assembly from the vehicle.
(See Engine and Transaxle Assembly - "Engine and Transaxle Assembly")
Remove the transaxle assembly from the engine assembly.
(Refer to Automatic Transmission System - Automatic Transmission)
Remove the drive plate.
(Refer to Cylinder Block - Drive Plate)
Remove the rear oil seal.
(See Cylinder Block - "Rear Oil Seal")
Install the engine on an engine stand for disassembly.
Remove the timing chain.
(See Timing System - Timing Chain)
Remove the water pump assembly.
(See Cooling System - "Water Pump")
Remove the water inlet pipe and thermostat assembly.
(See Cooling System - "Thermostat")
Remove the intake manifold.
(See Intake and Exhaust System - Intake Manifold)
Remove the air conditioning compressor.
(See Heating, Ventilation and Air Conditioning - "Compressor")
Remove the exhaust manifold.
(See Intake and Exhaust System - Exhaust Manifold)
Remove the cylinder head assembly.
(See Cylinder Head Assembly - Cylinder Head)
Remove the oil filter.
(See Lubrication System - Engine Oil)
Remove the oil screen.
(See Lubrication System - Oil Pan)
Check the connecting rod side clearance.
Check the oil clearance of the connecting rod bearing cap.
Remove the piston and connecting rod assembly.
Using a ridge reamer, remove all carbon from the top of the cylinder.
Remove the connecting rod bearing caps (A).
Push the piston and connecting rod assembly with the upper bearing through the top of the cylinder block.
Check the fit between the piston and piston pin.
Try to move the piston back and forth on the piston pin.
If any movement is felt, replace the piston and pin as a set.
Remove the piston rings.
Using a piston ring expander, remove the 2 compression rings.
Remove the 2 side rails and oil control ring by hand.
Remove the connecting rod from the piston.
Remove the snap ring (A) from the piston.
Remove the piston pin (B) from the piston.
Disassemble the piston (C) and connecting rod (D).
Inspection
Connecting Rod
Check the connecting rod side clearance.
Using a feeler gauge, measure the connecting rod side clearance while moving the connecting rod back and forth.
If out of specification, install a new connecting rod.
If still out of specification, replace the crankshaft.
Connecting rod side clearance Standard: 0.10–0.25 mm (0.0039–0.0098 in.)
Check the oil clearance of the connecting rod bearing.
Make sure the alignment marks on the connecting rod and cap are aligned to ensure correct assembly.
Remove the 2 connecting rod cap bolts.
Remove the connecting rod cap and lower bearing.
Clean the connecting rod journal and bearing.
Place a piece of Plastigage on the crankshaft journal.
Install the lower bearing and cap onto the connecting rod, then tighten the bolts.
Tightening Torque
Step 1:
17.7–21.6 N·m (1.8–2.2 kgf·m, 13.0–15.9 ft-lbf)
Step 2: 88–92°
Remove the connecting rod cap and lower bearing.
Measure the width of the Plastigage at its widest point.
Oil clearance: 0.028–0.046 mm (0.00110–0.00181 in.)
If the Plastigage reading is too wide or too narrow, remove the upper and lower bearings, then install new bearings with the same color code. Recheck the oil clearance.
If the Plastigage indicates that the clearance is still incorrect, try the next larger or smaller bearing. Recheck the oil clearance.
Connecting Rod Identification Mark
Connecting Rod Specifications
Grade Mark Inner Diameter 0 A 48.000 - 48.006 mm
(1.88976 - 1.89000 in.)1 B 48.006 - 48.012 mm
(1.89000 - 1.89023 in.)2 C 48.012 - 48.018 mm
(1.89023 - 1.89047 in.)
Crankshaft Pin Identification Mark
Crankshaft Specifications
Grade Mark Pin Outside Diameter I 1 44.966 - 44.972 mm
(1.77031 - 1.77055 in.)II 2 44.960 - 44.966 mm
(1.77008 - 1.77031 in.)III 3 44.954 - 44.960 mm
(1.76984 - 1.77008 in.)
Connecting Rod Bearing Identification Mark
Connecting Rod Bearing Specifications
Grade Mark Bearing Thickness A Light Blue 1.511 - 1.514 mm
(0.05949–0.05961 in.)B Black 1.508 - 1.511 mm
(0.05937–0.05949 in.)C White 1.505 - 1.508 mm
(0.05925–0.05937 in.)D Light Green 1.502 - 1.505 mm
(0.05913–0.05925 in.)E Pink 1.499 - 1.502 mm
(0.05902–0.05913 in.)Select the connecting rod bearing using the selection table.
Connecting Rod Bearing Selection Table
Bearing Classification Assembly Connecting Rod Marking 0 1 2 Crankshaft Marking I (1) E (Pink) D (Light Green) C (White) II (2) D (Light Green) C (White) B (Black) III (3) C (White) B (Black) A (Light blue)
Inspect the connecting rods.
When reinstalling, make sure the cylinder numbers stamped on the connecting rod and cap match those marked during disassembly. When installing a new connecting rod, make sure the notches that hold the bearing in place are on the same side.
Replace the connecting rod if it is damaged on the thrust surfaces at either end. Also, if the small end inner diameter shows stepped wear or a heavily roughened surface, the connecting rod must also be replaced.
Using a connecting rod aligner, check the connecting rod for bend and twist. If the measured value is close to the repair limit, straighten the connecting rod using a press. Any connecting rod that is severely bent or distorted must be replaced.
Allowable connecting rod bend:
0.05 mm (0.0020 in.) or less per 100 mm (3.94 in.)
Allowable connecting rod twist:
0.10 mm (0.0039 in.) or less for 100 mm (3.94 in.)
Piston
Clean the piston.
Using a gasket scraper, remove carbon deposits from the top of the piston.
Using a ring groove cleaning tool or a broken piston ring, clean the piston ring grooves.
Using solvent and a brush, thoroughly clean the piston.
Check the piston-to-cylinder clearance by calculating the difference between the cylinder bore diameter and the piston outer diameter.
Piston-to-cylinder clearance: 0.02–0.04 mm (0.0008–0.0016 in.)
Using a cylinder bore gauge, measure the cylinder bore diameter at positions in the thrust and axial directions.
Cylinder bore diameter: 81.00–81.03 mm (3.1890–3.1902 in.)
Measure the outer diameter of the piston at 35 mm (1.3780 in.) from the piston top land.
Piston outer diameter: 80.97–81.00 mm (3.1878–3.1890 in.)
Select a piston that matches the cylinder bore size class.
Piston-to-cylinder clearance: 0.02–0.04 mm (0.0008–0.0016 in.)
Check the cylinder bore size code on the cylinder block surface.
Cylinder bore inside diameter
Size code Cylinder Inner Diameter A 81.00–81.01 mm (3.1890–3.1894 in.) B 81.01–81.02 mm (3.1894–3.1898 in.) C 81.02–81.03 mm (3.1898–3.1902 in.) Check the piston size mark on the piston top surface.
Piston outside diameter
Size code Piston Outer Diameter A 80.97–80.98 mm (3.1878–3.1882 in.) B 80.98–80.99 mm (3.1882–3.1886 in.) C 80.99–81.00 mm (3.1886–3.1890 in.)
Piston Rings
Inspect the piston ring side clearance.
Using a feeler gauge, measure the clearance between a new piston ring and the ring groove wall.
If the clearance is greater than the maximum, replace the piston.
Piston Ring Side Clearance
[Standard]
No. 1 ring:
0.040–0.080 mm (0.00157–0.00315 in)
No. 2 ring:
0.040–0.080 mm (0.00157–0.00315 in)
Oil ring:
0.040–0.115 mm (0.00157–0.00453 in)
If the clearance is greater than the maximum, replace the piston.
Inspect the piston ring end gap.
To measure the piston ring end gap, insert the piston ring into the cylinder bore. Position the ring at a right angle to the cylinder wall by lightly pushing it with the piston. Measure the gap with a feeler gauge.
Piston Ring End Gap
[Standard]
No. 1 ring: 0.15–0.30 mm (0.0059–0.0118 in.)
No. 2 ring: 0.30–0.45 mm (0.0118–0.0177 in.)
Oil ring: 0.20–0.70 mm (0.0079–0.0276 in.)
If the clearance exceeds the service limit, replace the piston rings. If the clearance is still too large, re-measure the cylinder bore inside diameter. If the bore exceeds the service limit, replace the cylinder block.
Piston Pin
Measure the piston pin diameter.
Piston pin diameter: 19.997–20.000 mm (0.78728–0.78740 in.)
Measure the piston pin-to-piston clearance.
Clearance between piston pin and piston: 0.004–0.012 mm (0.00016–0.00047 in.)
Measure the clearance between the outer diameter of the piston pin and the inner diameter of the connecting rod small end.
Clearance between piston pin and connecting rod: 0.007–0.018 mm (0.00028–0.00070 in.)
Installation
Assemble the piston and connecting rod.
Install the snap ring (A) on one side of the piston pin hole.
Align the piston front mark with the connecting rod front mark.
Insert the piston pin (B) into the piston pin hole and the connecting rod small end hole.
Install the snap ring (C) on the other side after inserting the piston pin.
Install the piston rings.
Install the oil control ring spacer and 2 side rails by hand.
Using a piston ring expander, install the 2 compression rings with the manufacturer's mark facing up.
Position the piston rings so the ring gaps are as shown in the illustration. (No. 1 ring gap should be on the opposite side from the No. 2 ring gap.)
Example)
Install the connecting rod bearings.
Align the bearing tab with the groove in the connecting rod or connecting rod cap.
Install the bearings (A) in the connecting rod and connecting rod cap (B).
Install the piston and connecting rod assembly.
Before installing the piston, apply engine oil to the piston ring grooves and the cylinder bores.
Install the piston and connecting rod assembly with the front mark facing the front of the engine.
Install the ring compressor, make sure the rings are securely seated, then insert the piston into the cylinder and tap it in with the wooden handle of a hammer.
Stop after the piston ring compressor is released and check the alignment of the connecting rod with the crankpin before installing the piston in place.
Apply engine oil to the bolt threads. Install the connecting rod caps (A) with the bearings and tighten the bolts.
Tightening Torque
Step 1:
17.7–21.6 N·m (1.8–2.2 kgf·m, 13.0–15.9 ft-lbf)
Step 2: 88–92°
Check the connecting rod side clearance.
Assemble the remaining components in the reverse order of removal.
Test yourself
A quick Kia Optima DL3 quiz: every answer comes with an explanation and a link to the manual page.