Piston: Service and Repair

REMOVAL
1. Disconnect negative cable at battery.
2. Drain engine oil.
3. Drain coolant.
4. Remove cylinder head. Refer to item VALVES AND CYLINDER HEAD for removal.
5. Remove oil pump.
Refer to item OIL PUMP for removal.





6. Mark cylinder number on all pistons, connecting rods and connecting rod caps.
7. Remove rod bearing caps.
8. Install guide hose over threads of rod bolts. This prevents damage to bearing journal and rod bolt threads when removing connecting rod.
9. Clean carbon from top of cylinder bore before removing piston from cylinder.
10. 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
Cylinder
- 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 over size piston.





- Using a cylinder gauge, measure cylinder bore in thrust and axial directions at two positions as shown in figure.
If any of the 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: 84.050 mm (3.3090 inch)
Taper and out-of-round limit: 0.10 mm (0.004 inch)

NOTE: If any one of six cylinders has to be rebored, rebate 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 damages. Damaged or faulty piston should be replaced.
- Piston diameter:
As indicated in figure, piston diameter should be measured at a position 26.5 mm (1.04 inch) from piston skirt end in the direction perpendicular to piston pin.








- 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)
Oil: 0.06 - 0.15 mm (0.0023 - 0.0059 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: 21.003 - 21.011 mm (0.8269 - 0.8272 inch)
Piston pin diameter: 20.997 - 21.000 mm (0.8267 - 0.8267 inch)





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





NOTE: Clean carbon and any other dirt from 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. 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 crankpin 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: A - B
Taper limit: a - b
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 (0.0098 inch) undersize bearing. For identification of undersize bearing, it is painted red at the position as indicated in figure, undersize bearing thickness is 1.605 - 1.615 mm (0.0632 - 0.0635 inch) at the center of it.





- Rod bearing clearance:
1. Before checking bearing clearance, clean bearing and crank pin.
2. Install bearing in connecting rod and bearing cap.
3. Place piece of gaging plastic the full width of crank pin 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): 45 Nm (33.0 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.








Selection of Connecting Rod Bearing
STANDARD BEARING
If bearing is in malcondition, or bearing clearance is out of specification, select a new standard bearing according to following procedure and install it.
1. First check crank pin diameter.
There are numbers and alphabets stamped of crank web No.3 as shown in figure.
Three alphabets ("A", "B" and "C") represent following crank pin diameters.





2. Next check connecting rod bearing bore diameter without bearing. One of following number is stamped on the side of connecting rod big end. Three numbers ("1", "2" and "3") represent following cap bore diameters.








3. There are five kinds of standard bearings differing in thickness. To distinguish them, they are painted in following colors at the position as indicated in figure. Each color indicates following thickness at the center of bearing.





4. From alphabet stamped on crank web No.3 and the number stamped on connecting rod big end, determine new standard connecting rod bearing to be installed, by referring to table.
For example, if alphabet stamped on crank web No.3 is "B" and number stamped on connecting rod big end is "1", install a new standard bearing painted in "Black".





5. Using gaging plastic, check bearing clearance with newly selected standard bearing.
If clearance still exceeds its limit, use next thicker bearing and recheck clearance.
If clearance can not be still brought to within its limit even by using a new standard size bearing, regrind the crank pin to undersize and use 0.25 mm undersize bearing.

Crank pin diameter (0.25 mm undersize): 49.707 - 49.763 mm (1.9570 - 1.9591 inch)

6. When replacing crankshaft or connecting rod due to any reason, select new standard bearings to be installed by referring to alphabet stamped on new crankshaft or number stamped on big end of new connecting rod.





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 painted color of red and blue on the cylinder block as shown.





c) Stamped number on piston and stamped mark on cylinder block should correspond. That is, install number 2 stamped piston to cylinder which is identified with mark blue and a number 1 piston to cylinder with mark red.





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:
^ The "77E" mark on connecting rod should come on crankshaft pulley side.





^ Circlip should be installed with its cut part facing as shown in figure.





2. Install piston rings to piston:
- As indicated in figure at the left, 1st and 2nd rings have "RN" or "R" mark respectively. When installing these piston rings to piston, direct marked side of each ring toward top of piston.
- 1st rings 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
1. Apply engine oil to pistons, rings, cylinder walls, connecting rod bearings and crank pins.

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 crank pin 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): 45 Nm (33.0 ft. lbs.)

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