Piston: Service and Repair

Piston Assemblies - Engine Set

Service Repair No - 12.17.03.01

Remove
1. Remove cylinder head gaskets.
2. Remove connecting rod bearings.





3. With a socket and bar fitted to crankshaft pulley bolt, rotate crankshaft for access to the lubrication jets.
4. Remove Allen screws securing lubrication jets and remove the jets.

Disassembly





1. Mark connecting rod relative to its fitted position to aid reassembly.





2. Mark piston relative to its fitted position to aid reassembly.





3. Fit guides LRT-12-176 to connecting rod to protect cylinder bore and crankshaft journals.
4. Remove ridge of carbon from top of cylinder bore.
5. Carefully push piston assembly from cylinder bore.
6. Remove guides LRT-12-176 from connecting rod.





7. Hold connecting rods in a soft jawed vice.
8. Carefully remove and discard 2 retaining rings securing the gudgeon pin in the piston.
9. Push the gudgeon pin out of the piston and connecting rod, remove the piston.
10. Repeat for the 7 remaining pistons.

Inspect





1. Clean cylinder bores, pistons, piston rings connecting rods and gudgeon pins.
2. Pistons and cylinder bores: check and record cylinder bore diameters at bottom, centre and top of bore ensuring that measurements are taken at the angle shown.
3. Repeat procedure at angle shown and from the 2 sets of measurements obtained, calculate cylinder bore ovality and taper.





4. Starting with No 1 piston, measure and record piston diameter at right angles to gudgeon pin holes, and 12 mm from bottom of piston skirt:
5. Compare piston diameter with cylinder bore size and determine piston to bore clearance.
6. Using an expander, remove piston rings from piston.





7. Check new ring fitted gap 30 mm from top of bore. Ensure rings are fitted square to bore when checking gap.





8. Fit oil control ring rails and expander, ensuring ends butt and do not overlap.
9. Fit 2nd compression ring with"TOP" marking upwards.
10. Fit 1st compression ring with "TOP" marking upwards.





11. Check piston ring to groove clearance.
12. Check fit of gudgeon pin in piston, pin must be a tight, sliding fit with no perceptible side play.
13. Check small-end bushes for wear, check that gudgeon pin is a sliding fit in the bush with no perceptible side play.
Small end bushes cannot be replaced, a new connecting rod must be fitted.





14. Check parallelism of connecting rods on both sides taking the measurement approximately 150 mm from the centre line of the connecting rod
15. Check for distortion on both sides of connecting rod.

Reassembly
1. Clean cylinder bores, pistons, piston rings and connecting rods.





2. Fit each piston to its connecting rod ensuring that the arrow on the piston which points to the front of the engine is relative to the mark made on the connecting rod during disassembly.
3. Lubricate gudgeon pins and bushes with engine oil, fit gudgeon pins and secure with new retaining rings ensuring that they are fully seated in their grooves.
4. Lubricate pistons, piston rings and cylinder bores with clean engine oil.
5. Check that piston rings are free to rotate, position ring gaps at 120° to each other and away from the thrust side -LH side of piston - viewed from front of piston.





6. Using a piston ring clamp, compress piston rings.





7. Fit guides LRT-12-176 to connecting rod to protect cylinder bore and crankshaft journals.
8. Fit connecting rod and piston into cylinder bore. Ensure arrow on piston is facing towards the front of the cylinder block and dimples on connecting rods that share a journal face each other as shown.
9. Remove guides LRT-12-176 from connecting rod.

Refit
1. Clean lubricating jet and mating face.
2. Fit lubrication jets and tighten Allen screws to 10 Nm (7 ft. lbs.).
3. Fit connecting rod bearings.
4. Fit cylinder head gaskets.