Piston: Service and Repair

REMOVAL
1. Insert a 3/16 flat bladed screwdriver between the dust lip and the metal case of the crankshaft seal. Angle the screwdriver through the dust lip against metal case of the seal and pry out seal.

CAUTION: Do not permit the screwdriver blade to contact crankshaft seal surface. Contact of the screwdriver blade against crankshaft edge (chamfer) is permitted.

2. Remove the top ridge of cylinder bores with a reliable ridge reamer before removing pistons from cylinder block.

NOTE: Be sure to keep tops of pistons covered during this operation and mark the pistons with matching cylinder number.





3. Ensure the connecting rods and connecting rod caps match and are properly identified for the cylinder from which they came.





4. Pistons and connecting rods must be removed from the top of cylinder block. Rotate the crankshaft so that each connecting rod is centered in cylinder bore.
5. Remove connecting rod cap bolts. Push each piston and rod assembly out of cylinder bore.

NOTE: Be careful not to nick crankshaft journals.

6. After removal, install bearing cap properly on the mating connecting rod.





DISASSEMBLY
1. Separate piston from connecting rod by removing piston pin.
2. Using a suitable ring expander, remove upper and intermediate piston rings.
3. Remove the upper oil ring side rail, lower oil ring side rail and then oil ring expander from piston.
4. Clean ring grooves of any carbon deposits.





REASSEMBLY
1. Install rings with manufacturer's I.D. mark facing up, toward the top of the piston. Install piston rings in the following order:
a. Oil ring expander.
b. Upper oil ring side rail.
c. Lower oil ring side rail.
d. No. 2 intermediate piston ring.
e. No. 1 upper piston ring.
2. Install the side rail by placing one end between the piston ring groove and the expander. Hold end firmly and press down the portion to be installed until side rail is in position.

CAUTION: Do not use a piston ring expander.

3. Install upper side rail first and then the lower side rail.





4. Install No. 2 piston ring and then No. 1 piston ring.





5. Position piston ring end gaps as shown.
6. Position oil ring expander gap at least 45° from the side rail gaps but not on the piston pin center or in the thrust direction. Staggering ring gap is important for oil control.

INSTALLATION
1. Before installing pistons and connecting rod assemblies into the bore, be sure that compression ring gaps are staggered so that neither is in line with oil ring rail gap.





2. Before installing the ring compressor, make sure the oil ring expander ends are butted and the rail gaps located as shown.





3. Immerse the piston head and rings in clean engine oil and slide the ring compressor over the piston. Be sure that position of rings does not change during this operation.





4. The arrow should face toward the front of the engine. Install the pistons.
5. Rotate the crankshaft so that the connecting rod journal is on the center of the cylinder bore. Insert the rod and piston assembly into cylinder bore and guide rod over the crankshaft journal.
6. Tap the piston down in cylinder bore, using a hammer handle. At the same time, guide connecting rod into position on connecting rod journal.





7. Install connecting rod bearings selected based on the obtained connecting rod bearing clearance.
8. Install each bolt finger tight, then alternately torque each nut to assemble the cap properly.
9. Tighten the bolts to 27.0 Nm plus 1/4 turn (20 ft. lbs. plus 1/4 turn).

NOTE: Do not use a torque wrench for last step.





10. Using a feeler gauge, check connecting rod side clearance.
Standard value: 0.13 - 0.38 mm (0.005 - 0.015 inch).
Limit 0.37 mm (0.015 inch).

NOTE: If burr or scratch is present on the crankshaft edge (chamfer), cleanup with 400 grit sand paper to prevent seal damage during installation of new seal.





11. Place oil seal installation tool No. MB995059, or equivalent, on crankshaft. This is a pilot tool with a magnetic base.





12. Position seal over pilot tool. Make sure you can read the words "THIS SIDE OUT" on seal. Pilot tool should remain on crankshaft during installation of seal.

NOTE: When installing seal, no lube on seal is needed.





13. Drive the seal into the block using seal tool installer MB995060 and handle C-4171, or equivalent, until the tool bottoms out against the block.

CAUTION: If the seal is driven into the block past flush, this may cause an oil leak.