Piston and Connecting Rod
PISTON AND CONNECTING RODREMOVAL AND INSTALLATION
Removal Steps 1-14:
Required Special Tool:
^ MB992010: Bolt guide
REMOVAL SERVICE POINTS
[A] CONNECTING ROD CAP REMOVAL
1. Mark the cylinder number on the side of the connecting rod big end for correct reassembly.
2. Keep the removed connecting rods, caps, and bearings in order according to the cylinder number.
[B] PISTON AND CONNECTING ROD ASSEMBLY REMOVAL
1. Not to damage the crank pin, attach a special tool MB992010, to the connecting rod bolt.
2. Remove the piston and connecting rod assembly from the cylinder block.
[C] PISTON PIN REMOVAL
1. Remove the snap rings.
CAUTION
The clearance between the piston and the piston pin is a tight fit at room temperature. Therefore, be sure to heat the piston before pulling out the piston pin. Use care since the piston is hot after heating.
2. Heat the piston approximately 70 degrees C (158 degrees F) and pull out the piston pin.
INSTALLATION SERVICE POINTS
[A] PISTON PIN INSTALLATION
1. When replacing the piston, note the cylinder bore size mark on the cylinder block as illustrated, and select a piston according to the following table.
2. Set the snap ring into one side of the piston pin hole.
CAUTION
Apply ample coat of engine oil to the periphery of the piston pin and the hole of the connecting rod small end. The clearance between the piston and the piston pin is a tight fit at room temperature. Therefore, be sure to heat the piston before inserting the piston pin. Use care since the piston is hot after heating.
3. Heat the piston to approximately 70 degrees C (158 degrees F).
4. With the front mark of the connecting rod and that of the piston located on the same side, insert the piston pin.
5. Set the snap ring into the other side of the piston pin hole.
6. Check that the piston moves smoothly.
[B] OIL RING INSTALLATION
1. Fit the oil ring spacer into the piston ring groove.
NOTE: The side rails and spacer may be installed in either direction.
CAUTION
Do not use any piston ring expander when installing the side rail. It will break the side rail.
2. Install the upper side rail by hand.
To install the side rail, first fit one end of the rail into the piston groove, then press the remaining portion into the position. See illustration.
3. Install the lower side rail in the same procedure as described in step 2.
4. Make sure that the side rails move smoothly in both directions.
[C] PISTON RING NO.2 / PISTON RING NO.1 INSTALLATION
1. To prevent wrong installation, check the identification mark of each piston ring. The identification mark is stamped near the ring gap:
Identification mark
Number 1 ring: 1T
Number 2 ring: 2T
NOTE: Size marks on piston rings are as follows.
2. Using a piston ring expander, fit the number 2 piston ring into the number 2 groove of piston.
NOTE: Install the piston rings with their identification mark facing up, to the piston crown side.
3. Install the number 1 piston ring in the same manner as step 2.
[D] CONNECTING ROD BEARING INSTALLATION
1. Measure the crankshaft pin diameter and confirm its classification from the following table. In the case of a crankshaft supplied as a service part, identification colors of its pins are painted at the positions shown in the illustration.
2. From the above table, select a bearing whose size is appropriate for the crankshaft pin outside the diameter. For example, if the crankshaft pin outside diameter Identification color is "yellow," select a bearing whose Identification color is "pink."
If there is no identification color paint on the crankshaft, measure the pin outside diameter and select bearing appropriate for the measured value.
3. Install the selected bearing in the big end and in the cap of the connecting rod.
[E] PISTON AND CONNECTING ROD ASSEMBLY INSTALLATION
1. Liberally coat the circumference of the piston, piston ring, and oil ring with engine oil.
2. Arrange the piston ring and oil ring gaps (side rail and spacer) as shown in the illustration.
3. Rotate the crankshaft so that the crank pin is on the center of the cylinder bore.
4. Insert the piston and connecting rod assembly into the cylinder with the front mark on the piston crown pointing to the timing belt side.
5. Not to damage the crank pin, attach a special tool MB992010, to the connecting rod bolt.
6. Using a suitable piston ring compressor tool, install the piston and connecting rod assembly into the cylinder block.
[F] CONNECTING ROD CAP INSTALLATION
1. Verifying the mark made during disassembly, install the bearing cap to the connecting rod. If the connecting rod is new with no index mark, make sure that the bearing locking notches are on the same side as shown.
2. Make sure that the connecting rod big end side clearance meets the specification.
Standard value: 0.10 - 0.25 mm (0.003 - 0.009 inch)
Limit: 0.4 mm (0.02 inch)
[G] CONNECTING ROD CAP NUT INSTALLATION
1. The connecting rod bolts should be examined before reuse. If the bolt threads are damaged, the bolt should be replaced. Hand-thread the nut to the full length of the bolt threads. If the nut does not run down smoothly, the bolt should be replaced.
2. Before installation of each nut, apply engine oil to the threaded portion and bearing surface of the nut.
3. Loosely tighten each nut to the bolt.
4. Then tighten the nuts alternately to a torque of 27 ± 2 Nm (20 ± 1 ft-lb) to install the cap properly.
5. Make a paint mark on the head of each nut.
6. Make a paint mark on the bolt end at a position 90 to 94 degrees from the paint mark made on the nut in the direction of tightening the nut.
CAUTION
^ If the nut is turned less than 90 degrees, proper fastening performance may not be achieved. Be careful to tighten the nut exactly 90 degrees.
^ If the nut is overtightened (exceeding 94 degrees), loosen the nut completely and then retighten it by repeating the tightening procedure from step 3.
7. Turn the nut another 90 to 94 degrees and make sure that the paint marks on the nut and bolt are aligned.
INSPECTION
PISTON
Replace the piston if scratches or seizure is evident on its surfaces (especially the thrust surface). Replace the piston if it is cracked.
PISTON PIN
1. Insert the piston pin into the piston pin hole with a thumb. You should feel a slight resistance. Replace the piston pin if it can be easily inserted or there is excessive play.
2. The piston and piston pin must be replaced as an assembly.
PISTON RING
1. Check the piston ring for damage, excessive wear, and breakage. Replace if defects are evident. If the piston has been replaced with a new one, the piston rings must also be replaced with new ones.
2. Check for clearance between the piston ring and ring groove. If the limit is exceeded, replace the ring or piston, or both.
Standard value:
Number 1: 0.03 - 0.07 mm (0.0012 - 0.0027 inch)
Number 2: 0.02 - 0.06 mm (0.0008 - 0.0023 inch)
Limit: 0.1 mm (0.003 inch)
3. Insert the piston ring into the cylinder bore. Force the ring down with a piston, the piston crown being in contact with the ring, to correctly position it at right angles to the cylinder wall. Then, measure the end gap with a feeler gauge. If the ring gap is excessive, replace the piston ring.
Standard value:
Number 1: 0.25 - 0.40 mm (0.010 - 0.016 inch)
Number 2: 0.35 - 0.50 mm (0.014 - 0.020 inch)
Oil: 0.10 - 0.35 mm (0.003 - 0.014 inch)
Limit:
Number 1, Number 2: 0.8 mm (0.03 inch)
Oil: 1.0 mm (0.03 inch)
CRANKSHAFT PIN OIL CLEARANCE [PLASTIGAGE METHOD]
The crankshaft oil clearance can be measured easily by using plastigage, as follows:
1. Remove oil from the crankshaft pin and the bearing inner surface.
2. Cut plastigage to the same length as the width of the bearing and place it on the pin in parallel with its axis.
3. Install the connecting rod cap carefully and tighten the nuts to the specified torque.
4. Carefully remove the connecting rod cap.
5. Measure the width of the smashed plastigage at its widest section by using a scale printed on the plastigage bag.
Standard value: 0.020 - 0.038 mm (0.0008 - 0.0015 inch)
Limit: 0.1 mm (0.003 inch)