A) Check the outer surface.
b) Use a scraper to remove carbon deposits and other carbon deposits from the piston crown.
V) Clean the piston grooves of deposits with part of the broken ring.
G) Clean the plunger with a thinner with a soft brush.
Note: Do not use a metal brush.
2. Check the piston and piston rings.
A. Check clearance between piston and cylinder.
A) Using a micrometer, measure the piston skirt diameter in a direction perpendicular to the axis of the piston pin as shown in the figure.
- Distance "L" - 20 mm
Piston diameter:
- nominal size - 92.918 - 92.944 mm
repair size:
- (0,25) - 93.153-93.179 mm
- (0,50) - 93.403 - 93.429 mm
b) Find the difference between the piston and cylinder diameters. Determine the size of the gap.
- Nominal clearance - 0.071 - 0.089 mm
- Maximum clearance - 0.15 mm
If clearance is greater than maximum, replace all pistons. Replace the cylinder block if necessary.
Note: When replacing pistons, piston rings must also be replaced.
B. Check end clearance "piston ring - piston groove", by measuring it with a flat feeler gauge as shown in the figure.
Rated Clearance:
- compression ring No. 1 - 0.06 -0.10 mm
- compression ring No. 2 - 0.04 - 0.08 mm
- oil scraper ring - 0.02 - 0.06 mm
Maximum clearance - 0.15 mm
If the clearance is greater than allowable, replace the piston and piston rings.
B. Check the clearance in the piston ring lock.
A) Insert the piston ring into the cylinder.
b) Use the piston to push the ring away from the surface of the cylinder block as shown.
V) Use a flat feeler gauge to measure the gap in the ring lock.
Rated Clearance:
- compression ring No. 1 - 0.22 - 0.32 mm
- compression ring No. 2 - 0.49 - 0.64 mm
- oil scraper ring - 0.22 - 0.52 mm
Maximum clearance - 1.00 mm
If the gap in the lock is greater than the maximum, replace the piston ring and repeat the test again. If the clearance is still greater than the maximum, replace the cylinder block.
3. Check up concentricity of heads of a rod.
A. Using the special tool and a feeler gauge, check the bending of the connecting rod as shown in the illustration.
- The maximum allowable bend per 50 mm length is 0.075 m/m
- The maximum allowable twist per 50 mm length is 0.18 mm
- Connecting rod length - 162.96 - 163.04 mm
If bending or twisting is excessive, replace the connecting rod along with the connecting rod cap.
B. Check the distance between the axis of the piston pin and the axis of the connecting rod journal.
- Center distance - 162.96-163.03 mm
B. Check piston pin oil clearance.
A) Using a micrometer, measure the diameter of the piston pin in the directions "X" And "Y", as it shown on the picture.
- Nominal piston pin diameter - 33.994 - 34.000 mm
b) Using a inside gauge, measure the inner diameter of the upper head of the connecting rod in the directions "X" And "Y", as it shown on the picture.
- Nominal diameter - 34.012 - 34.033 mm
V) Determine the oil clearance: subtract the piston pin diameter from the inside diameter of the connecting rod.
- Nominal clearance —0.012 - 0.039 mm
If necessary, replace the connecting rod or piston pin.
4. Check the piston pin oil clearance and piston pin bores in the piston boss.
A) Measure the diameter of the piston pin hole in the piston boss.
- Nominal diameter - 33.997 - 34.007 mm
b) Find the difference between the diameters of the piston pin and the piston pin hole.
- Oil clearance - 0.003 - 0.013 mm
Replace piston and/or piston pin if necessary.