Piston: Service and Repair

PISTON, PISTON RINGS, CONNECTING RODS AND CYLINDERS

REMOVAL
1. Remove cylinder head from cylinder block.
2. Drain engine oil.
3. Remove oil pan and oil pump strainer.
4. Mark cylinder number on all pistons, connecting rods anti rod bearing caps, using silver pencil or quick drying paint.





5. Remove rod bearing caps.
6. Install guide hose over threads of rod bolts. This is to prevent damage to bearing journal and rod bolt threads when removing connecting rod.
7. Decarbon top of cylinder bore before removing piston from cylinder.
8. Push piston and connecting rod assembly out through the top of cylinder bore.

DISASSEMBLY
1. Using piston ring expander, remove two compression rings (Top and 2nd) and oil ring from piston.





2. Remove piston pin from connecting rod.
- Ease out piston pin circlips, as shown.





- Force piston pin out.

CLEANING
Clean carbon from piston head and ring grooves, using a suitable tool.

INSPECTION
Cylinders
- Inspect cylinder walls for scratches, roughness, or ridges which indicate excessive wear. If cylinder bore is very rough or deeply scratched, or ridged, rebore cylinder and use oversize piston.





- Using a cylinder gauge, measure cylinder bore in thrust and axial directions at two positions as shown in figure. If any of following conditions is noted, rebore cylinder.
1. Cylinder bore diameter exceeds limit.
2. Difference of measurements at two positions exceeds taper limit.
3. Difference between thrust and axial measurements exceeds out-of-round limit.

Cylinder bore diameter limit: 75.15 mm (2.9586 inch)
Tapper and out-of-round limit: 0.10 mm (0.0039 inch)

NOTE: If any one of four cylinders has to be rebored, rebore all four to the same next oversize. This is necessary for the sake of uniformity and balance.





Pistons
- Inspect piston for faults, cracks or other damaged. Damaged or faulty piston should be replaced.





- Piston diameter:
As indicated in figure, piston diameter should be measured at a position 15 mm (0.59 inch) from piston skirt end in the direction perpendicular to piston pinch





- Piston clearance:
Measure cylinder bore diameter and piston diameter to find their difference which is piston clearance. Piston clearance should be within specification as given below. If it is out of specification, rebore cylinder and use oversize piston.

Piston clearance: 0.02 - 0.04 mm (0.0008 - 0.0015 inch)

NOTE: Cylinder bore diameters used here are measured in thrust direction at two positions.





- Ring groove clearance:
Before checking, piston grooves must be clean, dry and free of carbon.
Fit new piston ring into piston groove, and measure clearance between ring and ring land by using thickness gauge. If clearance is out of specification, replace piston.

Ring groove clearance:
Top: 0.03 - 0.07 mm (0.0012 - 0.0027 inch)
2nd: 0.02 - 0.06 mm (0.0008 - 0.0023 inch)





Piston Pin
- Check piston pin, connecting rod small end bore and piston bore for wear or damage, paying particular attention to condition of small end bore bush. If pin, connecting rod small end bore or piston bore is badly worn or damaged, replace pin, connecting rod or piston.





- Piston pin clearance:
Check piston pin clearance in small end. Replace connecting rod if its small end is badly worn or damaged or if measured clearance exceeds limit.

Small-end bore: 19.003 - 19.011 mm (0.7482 - 0.7486 inch)
Piston pin diameter: 18.995 - 19.000 mm (0.7479 - 0.7480 inch)





Piston Rings
To measure end gap, insert piston ring into cylinder bore and then measure the gap by using thickness gauge.
If measured gap is out of specification, replace ring.





NOTE: Decarbon and clean top of cylinder bore before inserting piston ring.





Connecting Rod





- Big-end side clearance: Check big-end of connecting rod for side clearance, with rod fitted and connected to its crank pin in the normal manner. If measured clearance is found to exceed its limit, replace connecting rod.
- Connecting rod alignment:
Mount connecting rod on aligner to check it for bow and twist and, if limit is exceeded, replace it.

Limit on bow: 0.05 mm (0.0020 inch)
Limit on twist: 0.10 mm (0.0039 inch)





Crank Pin and Connecting Rod Bearings
- Inspect crank-pin for uneven wear or damage. Measure crank pin for out-of-round or taper with a micrometer. If crank pin is damaged, or out-of-round or taper is out of limit, replace crankshaft or regrind crank pin to undersize and use undersize bearing.





Out-of-round and taper limit: 0.01 mm (0.0004 inch)





- Rod bearing:
Inspect bearing shells for signs of fusion, pitting, burn or flaking and observe contact pattern. Bearing shells found in defective condition must be replaced.
Two kinds of rod bearing are available; standard size bearing and 0.25 mm undersize bearing. To distinguish them, 0.25 mm undersize bearing has the stamped number (US025) on its backside as indicated in figure, but standard size one has no number.





- Rod bearing clearance:
1. Before checking bearing clearance, clean bearing and crank pinch
2. Install bearing in connecting rod and bearing cap.
3. Place a piece of gaging plastic the full width of crankpin as contacted by bearing (parallel to crankshaft), avoiding oil hole.





4. Install rod bearing cap to connecting rod.
When installing cap, be sure to point arrow mark on cap to crankshaft pulley side, as shown in figure. After applying engine oil to rod bolts, tighten cap nuts to specified torque. DO NOT turn crankshaft with gaging plastic installed.

Tightening Torque (a): 35 Nm (25.5 ft. lbs.)





5. Remove cap and using a scale on gaging plastic envelope, measure gaging plastic width at the widest point (clearance).
If clearance exceeds its limit, use a new standard size bearing and remeasure clearance.





6. If clearance can not be brought to within its limit even by using a new standard size bearing, regrind crankpin to undersize and use 0.25 mm undersize bearing.





ASSEMBLY

NOTE: Two sizes of piston are available as standard size spare part so as to ensure proper piston-to-cylinder clearance. When installing a standard size piston, make sure to match piston with cylinder as follows.

a. Each piston has stamped number 1 or 2 as shown. It represents outer diameter of piston.
b. There are also stamped numbers of 1 and 2 on the cylinder block as shown. The first number represents inner diameter of No.1 cylinder, the second number of No.2 cylinder, the third number of No.3 cylinder and the fourth number of No.4 cylinder.





c. Stamped number on piston and that on cylinder block should correspond. That is, install number 2 stamped piston to cylinder which is identified with number 2 and a number 1 Piston to cylinder with number 1.





Also, a letter A, B or C is stamped on piston head but ordinarily it is not necessary to discriminate each piston by this letter.





1. Install piston pin to piston and connecting rod:
After applying engine oil to piston pin and piston pin holes in piston and connecting rod, fit connecting rod to piston as shown in figure and insert piston pin to piston and connecting rod, and install piston pin circlips.

NOTE: Circlip should be installed with its cut part facing either up or down as shown in figure.





2. Install piston rings to piston:
- As indicated in figure at the left, 1st and 2nd rings have "RN", "T" or "R" mark respectively. When installing these piston rings to piston, direct marked side of each ring toward top of piston.
- 1st ring differs from 2nd ring in thickness, shape and color of surface contacting cylinder wall.
Distinguish 1st ring from 2nd ring by referring to figure.
- When installing oil ring, install spacer first and then two rails.





3. After installing three rings (1st, 2nd and oil rings), distribute their end gaps as shown in figure.

INSTALLATION OR CONNECTION
1. Apply engine oil to pistons, rings, cylinder walls, connecting rod bearings and crankpins.

NOTE: Do not apply oil between connecting rod and bearing or between bearing cap and bearing.





2. Install guide hoses over connecting rod bolts.
These guide hoses protect crankpin and threads of rod bolt from damage during installation of connecting rod and piston assembly.





3. When installing piston and connecting rod assembly into cylinder bore, point arrow mark on piston head to crankshaft pulley side.





4. Install piston and connecting rod assembly into cylinder bore. Use special tool (Piston ring compressor) to compress rings. Guide connecting rod into place on crankshaft. Using a hammer handle, tap piston head to install piston into bore. Hold ring compressor firmly against cylinder block until all piston rings have entered cylinder bore.
Special Tool (A): 09916-77310





5. Install bearing cap: Point arrow mark on cap to crankshaft pulley side. Tighten cap nuts to specification.

Tightening Torque (a): 35 Nm (25.5 ft. lbs.)

6. Reverse removal procedure for installation.
7. Adjust water pump drive belt tension.
8. Adjust power steering pump belt tension or A/C compressor belt tension, if equipped.
9. Adjust accelerator cable play and A/T kickdown cable (for 3 A/T model) or A/T throttle cable (for 4 A/T model) play.
10. Check to ensure that all removed parts are back in place. Reinstall any necessary parts which have not been reinstalled.
11. Refill engine with engine oil, referring to item ENGINE OIL CHANGE.
12. Refill cooling system.
13. Refill front differential housing with gear oil, referring to DIFFERENTIAL.
14. Connect negative cable at battery.
15. Check ignition timing and adjust as necessary.
16. Verify that there is no fuel leakage, coolant leakage, oil leakage and exhaust gas leakage at each connection.