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MBE 4000 PISTON, PISTON RING, AND CONNECTING ROD

The pistons are made of aluminum alloy with ring carriers and a shallow combustion chamber recess. The pistons are cooled by oil spray nozzles. See Figure 41980 for an exploded view of the piston and connecting rod assembly. ‪

1. Piston and Rings ‪

5. Bearing Cap ‪

2. Wrist Pin ‪

6. Connecting Rod Stretch Bolt ‪

3. Snap Ring ‪

7. Bearing Shell ‪

4. Connecting Rod ‪

Piston Assembly (exploded view)

Piston Removal

Remove the piston assembly as follows: ‪

  1. Remove the engine from the vehicle.

    Note: The MBE 4000 engine has individual heads for each cylinder. To remove one piston, do these procedures step by step. To remove all the pistons, repeat each step in these instructions, as applicable, for all six pistons.

  2. Remove each cylinder head, as required. Refer to section .
  3. Remove the oil pan. Refer to section .

    NOTICE:

    Do not damage the piston travel surface of the cylinder.

  4. Using a plastic scraping tool, carefully scrape off any combustion residues from the combustion area in the cylinder in order to avoid damage to the piston rings when the piston is removed.
  5. Install the engine cranking tool (J 46167 or 407 589 00 63 00) . Refer to section .
  6. Be sure the connecting rods and the bearing caps are marked so that they can be matched for installation. See Figure 41981 .

    1. Bearing Cap ‪

    2. Connecting Rod ‪

    Checking Rod and Bearing Cap Markings

  7. Remove and inspect the oil spray nozzles. See Figure 41982 . Refer to section . Replace them if damaged.

    1. Oil Spray Nozzle ‪

    2. Cylinder Liner ‪

    Location of Oil Spray Nozzle

  8. Remove the connecting rod stretch bolts and bearing cap. See Figure 41983 .

    Removing the Bearing Caps

    Note: If the bearing shell halves are removed from the rods and caps, be sure to mark them so they can be matched for installation.

  9. Remove the bearing shell halves from the bearing cap and connecting rod.
  10. Push the piston and connecting rod out of the cylinder, and remove them both from the cylinder block.
  11. Secure the connecting rod in a vise with protective jaws.

    NOTICE:

    Be sure the vise jaws are adequately lined to prevent the rod surface from being nicked or marred in any way. Such surface damage could lead to later rod cracking or breaking.

  12. Remove the piston rings from the piston. Refer to section .
  13. Remove the wrist-pin snap rings. Push the wrist pin out and remove the piston from the connecting rod.

Piston Installation

Install the piston assembly as follows: ‪

  1. Position the connecting rod in the piston so that the longer end side is on the unit pump side (left side), and the arrow on the crown of the piston points toward the front of the engine.
  2. Install the wrist pin in the piston. See Figure 41984 .

    1. Piston ‪

    2. Wrist Pin ‪

    Installing the Wrist Pin

    1. Lubricate the wrist pin with a light coating of clean engine oil.
    2. Insert the wrist pin into the wrist pin bore.
    3. Secure the wrist pin with the two snap rings.
  3. Install the piston rings on the piston. See Figure 41985 . Refer to section .

    1. Piston ‪

    Ring Gaps Offset 120 Degrees

    1. Lubricate the piston with a light coating of clean engine oil.
    2. Install each piston ring in the appropriate groove on the piston.
  4. Offset the ring gaps alternately by 120 degrees.
  5. Position a ring compressor loosely over the piston. Tighten the ring compressor on the piston.

    NOTICE:

    The half of the bearing shell installed in the connecting rod (rod half) has a specially-treated friction surface that allows it to bear higher loads. It cannot be interchanged (swapped) with the other half of the bearing shell installed in the bearing cap (cap half).

  6. Install the rod half of the bearing shell in the connecting rod, as marked on removal. See Figure 41986 .

    1. Connecting Rod ‪

    3. Bearing Cap ‪

    2. Bearing Shells ‪

    Installing the Bearing Shells

    1. Be sure that the locking lug in the bearing shell is fully seated in the groove of the rod.
    2. Lubricate the bearing surface with a light coating of clean engine oil.
  7. Lubricate the cylinder liners with a light coating of clean engine oil.

    NOTICE:

    Be careful not to scratch the crankshaft journals with the connecting rod. This can lead to premature wear of the crankshaft.

  8. With the piston arrow pointing toward the front of the engine, push the piston into the cylinder until the rod bearing rests on the crankshaft journal. See Figure 41987 .

    1. Ring Compressor ‪

    3. Cylinder Block ‪

    2. Piston ‪

    Installing a Piston

  9. Install the cap half of the bearing shell in the bearing cap, as marked on removal. See Figure 41986 .
    1. Be sure that the locking lug in the bearing shell is fully seated in the groove of the cap.
    2. Lubricate the bearing surface with a light coating of clean engine oil.
  10. Measure the connecting rod stretch bolts. Replace any bolts that exceed the maximum length of 68.5 mm (2.70 inches). See Figure 41988 . Lubricate the stretch bolt threads with a light coating of engine oil.

    1. Shank ‪

    Measuring a Stretch Bolt

  11. Install the bearing cap on the connecting rod and hand-tighten the stretch bolts. Be sure that the marks on the cap and the rod match. See Figure 41981 .
  12. Tighten the M16 x 1.5 connecting rod stretch bolts alternately. Tighten each one in turn to the first stage and then go on to the next stage. Listed in Table .

    Max. Shaft Length ‪

    Tightening Stage ‪

    Torque Value ‪

    68.5 mm (2.70 in.) ‪

    Stage 1 ‪

    100-115 Nm (74-85 lbft) ‪

    Stage 2 ‪

    additional 90-100 ‪

    Tightening Stages, Connecting Rod Stretch Bolts
  13. Check the connecting rod end play (axial play). Refer to section .
  14. Rotate the crankshaft to make sure it turns freely.

    Note: If it is necessary to turn the crankshaft and the flywheel has been removed, install the flywheel guide studs in the crankshaft gear.

  15. Using a dial gauge and holder, measure the piston projection relative to crankcase top dead center at all the pistons. See Figure 41989 .

    1. Piston ‪

    2. Cylinder Liner ‪

    Piston Projection at Top Dead Center (TDC)

  16. If the piston projection dimensions are not between 0.244 and 0.715 mm (0.0096 and 0.0281 inch), replace the piston. Listed in Table .

    Description ‪

    mm (in.) ‪

    Piston Projection (from TDC) ‪

    0.244 to 0.715 (0.0096 to 0.0281) ‪

    Piston Projection Specifications
  17. Remove the engine cranking tool (J 46167 or 407 589 00 63 00) .

    NOTICE:

    Be careful not to damage the oil spray nozzles. Damaged oil spray nozzles could result in a loss of oil pressure and cause engine damage.

  18. Install the oil spray nozzles, as removed. Be sure they are seated and aligned correctly. Refer to section .
  19. Install the oil pan. Refer to section .
  20. Install each cylinder head, as removed. Refer to section .
  21. Install the engine in the vehicle.

Piston Ring Replacement

Replace the piston ring as follows: ‪

  1. Remove the piston. Refer to section .
  2. Remove the rings, using suitable ring pliers.

    Remove the rings in order, starting from the top of the piston down. See Figure 41990 . See Figure 41991 . ‪

    1. Keystone Piston Ring (Groove I) ‪

    3. Double Chamfered Oil Control Ring with Garter Spring (Groove III) ‪

    2. Taper Face Ring with Internal Angle (Groove II) ‪

    4. Piston ‪

    Piston Rings

    1. Piston ‪

    2. Ring Pliers ‪

    Removing the Piston Rings

  3. Clean all the carbon from the ring grooves. Be sure the grooves are not damaged, and that there are no burrs or combustion residue in the grooves.
  4. Before installing the new rings, check the end gap. The correct end-gap measurements are listed in Table .

    Ring Designation

    Groove

    Gap When New, mm (inch)

    Maximum End Gap, mm (inch)

    Keystone ‪

    I ‪

    0.45 to 0.60 ‪

    (0.018 to 0.024) ‪

    1.0 (.039) ‪

    Taper-Faced with Internal Angle ‪

    II ‪

    0.40 to 0.55 ‪

    (0.016 to 0.022) ‪

    1.0 (.039) ‪

    Double-Chamfered Oil Control with Garter Spring ‪

    III ‪

    0.40 to 0.55 ‪

    (0.016 to 0.022) ‪

    1.0 (.039) ‪

    Piston Ring End-Gap Dimensions

    Note: Check the end gap of the upper two piston rings first. The garter spring must be removed from the third (lowest) piston ring before you can measure its end gap.

    1. Place each ring squarely into the combustion area of a cylinder liner or cylinder, then measure the end gap, using a feeler gauge. See Figure 41992 .
    2. Checking the Ring End Gap

    3. Remove the spring garter from the third (lowest) ring, then measure its gap in the same way as the other two rings.
    4. Install the spring garter into the ring. The garter spring joint should be positioned 180 degrees from the gap in the piston ring. See Figure 41993 .
    5. 1. Garter Spring ‪

      3. Garter Spring Joint ‪

      2. Piston Ring ‪

      Installing the Garter Spring

  5. Using ring pliers, install the rings.

    Make sure the word "TOP" on each ring is facing toward the crown of the piston. Install the rings in the reverse order of their removal; from the bottom to the top of the piston. ‪

  6. Offset the ring gaps alternately by 120 degrees. See Figure 41994 .

    Piston ‪

    Piston Rings Offset 120 Degrees

  7. Install the piston. Refer to section .
Piston Inspection

Inspect the piston as follows: ‪

  1. Remove the piston. Refer to section .
  2. Check the diameter of the wrist pin and the wrist pin bore. See Figure 41980 . Specifications are listed in Table .

    1. Piston and Rings ‪

    5. Bearing Cap ‪

    2. Wrist Pin ‪

    6. Connecting Rod Stretch Bolt ‪

    3. Snap Ring ‪

    7. Bearing Shell ‪

    4. Connecting Rod ‪

    Piston Assembly (exploded view)

    Description

    Dimensions: mm (inch)

    Piston Compression Height ‪

    79.50-79.55 (3.130-3.132) ‪

    Wrist Pin Bore Diameter ‪

    52.03-52.04 (2.0484-2.0488) ‪

    Wrist Pin Diameter ‪

    51.992-51.998 (2.0469-2.0472) ‪

    Piston Inspection Specifications
  3. Inspect the cylinder liner and piston for damage and signs of wear. Replace any piston with damage to the snap ring grooves, cracks in the piston wall, or signs of seizing and/or erosion.
  4. Check the tolerance code on the piston and compare it to the tolerance code on the cylinder liner. See Figure 42005 .

    1. Piston ‪

    2. Cylinder Liner ‪

    Tolerance Codes

  5. Check the condition of the piston rings. Replace any worn, damaged, or chipped rings. Refer to section .
  6. Check the connecting rod for any unusual condition. Refer to section .
  7. Measure the diameters of the bearing shell bore and crankshaft journals. Refer to section for instructions.
  8. Check the length of the connecting rod stretch bolts. See Figure 41988 . Replace any bolts that exceed the maximum length of 68.5 mm (2.70 inches).

    1. Shank ‪

    Measuring a Stretch Bolt

Connecting Rod End Play Measurement

Measure the connecting rod end play as follows: ‪

  1. Remove the piston. Refer to section .
  2. Inspect the connecting rod for blue discoloration (indicates bearing damage), scoring, notches, and cracks. If any of these conditions are found, replace the connecting rod.
  3. Measure the inside diameter of the bushing in the small bore of the connecting rod. Use a quick-release caliper (internal measurement, 40 to 60 mm), with a dial gauge and holder.

    If the value exceeds 52.07 mm (2.050 inches), replace the connecting rod. ‪

    1. Dial Gauge ‪

    5. Bearing Shell (2 halves) ‪

    2. Dial Gauge Holder ‪

    6. Bearing Cap ‪

    3. Bushing ‪

    7. Stretch Bolt (2 qty.) ‪

    4. Connecting Rod ‪

    Measuring Inside Diameters in the Connecting Rod

    Note: Checking the connecting rod for a twisted or bent condition in the next step requires machine shop equipment such as a caliper gauge with a round scale.

    NOTICE:

    Do not attempt to straighten the connecting rod. This could result in severe engine damage.

  4. Inspect the connecting rod for twisting and dimensional tolerance. see Figure 41996 . If any value exceeds those listed in Table , , replace the connecting rod.

    Connecting Rod Measurements

    Description

    Dimensions: mm (inch)

    Length of Connecting Rod ‪

    255.970-256.030 (10.0775-10.0799) ‪

    Basic Bore Diameter for Connecting Rod Bearings ‪

    99.000-99.022 (3.8976-3.8985) ‪

    Maximum Permissible Out-of-Round in Bearing Bore ‪

    0.01 (0.0004) ‪

    Maximum Permissible Out-of-Round in Bushing Bore ‪

    0.01 (0.0004) ‪

    Maximum Difference in Axial Parallelism Between Bearing Bore and Bushing Inner Surface ‪

    0.030 (0.0012) ‪

    Width of Connecting Rod (at big end) ‪

    44.308-44.370 (1.744-1.7468) ‪

    Width of Connecting Rod Journal ‪

    44.5-44.6 (1.75-1.76) ‪

    Distance from Connecting Rod Center Line for Measuring Parallelism ‪

    50 (2) ‪

    Connecting Rod Dimensional Tolerances
    1. On each side of the connecting rod, measure the length of the connecting rod (Dimension A in see Figure 41996 ) : the distance from the center bearing bore (big-end bore) to the center of the bushing (small-end bore). The measurement must be within 255.970 to 256.030 mm (10.0775 to 10.0799 in.).
    2. Measure the difference in axial parallelism (Dimension B in see Figure 41996 ) between the bearing bore and the inner surface of the bushing, at 50 mm (2 inches) from the connecting-rod centerline (Dimension C in see Figure 41996 ). The maximum allowed difference is 0.030 mm (0.0012 inch).
    3. Measure the diameter of the connecting rod basic bore, with the bearing shells removed. The diameter of the basic bore must be between 99.000 to 99.022 mm (3.8976 to 3.8985 in.).
    4. Measure the maximum permissible out-of-round in the bearing bore, with the bearing shells removed. The maximum permissible is 0.01 mm (0.0004 in.).
  5. Calculate the connecting rod end play, or axial play, (fore-to-aft movement) on the crankshaft.

    If the end play is less than 0.130 mm (0.0051 inch), or more than 0.292 mm (0.0115 inch), replace the connecting rod. Listed in Table . ‪

    1. For each bearing journal, note the width (thickness) of the bearing journal. Example: Wj = 1.8120 inches.
    2. For each connecting rod, note the width (thickness) of the rod. Example: Wr = 1.8050 inches.
    3. From the value for the journal width, subtract the value for the connecting rod width. This result is the end play. Example: Wj Wr = 0.0070 inch.
  6. Remove the bolts and bearing cap when ready to install the piston.
  7. Install the piston. Refer to section .
Connecting Rod Radial Play Measurement

Measure the connecting rod radial play as follows: ‪

  1. Remove the piston. Refer to section .
  2. Using a chamois cloth, clean the bearing bores in both the connecting rod and the bearing cap.
  3. Install the two matched halves of the bearing shell, as marked on removal, into the connecting rod and into the bearing cap. Be sure the locking lugs on the bearing shells fit into the grooves in the rod and cap. See Figure 41997 .

    1. Connecting Rod ‪

    3. Bearing Cap ‪

    2. Bearing Shell (2 halves) ‪

    4. Connecting Rod Bolt ‪

    Bearing Shell Replacement

  4. Install the bearing cap on the connecting rod, pressing it on by hand. Be sure that the marks on the cap and rod match.
  5. Lubricate the threads and the contact surface of the head of each stretch bolt with a light coating of engine oil.
  6. Install the stretch bolts in the connecting rod, and tighten them alternately. Tighten each one in turn to the first stage and then go on to the next stage, listed in Table .

    Max. Shaft Length

    Tightening Stage

    Torque Value

    68.5 mm (2.70 in) ‪

    Stage 1 ‪

    108 Nm (80 lbft) ‪

    68.5 mm (2.70 in) ‪

    Stage 2 ‪

    additional 90 degrees ‪

    Tightening Stages, Connecting Rod Stretch Bolts
  7. Using a micrometer, measure the bearing journal on the crankshaft in both the vertical and horizontal plane and note the measurements. See Figure 41998 to locate the measuring points and listed in Table are the current repair stage specifications.

    Measuring the Bearing Journal

    Repair Stage: mm (in.)

    Diameter: mm (in.)

    Standard ‪

    93.980-94.000 (3.7000-3.7007) ‪

    Undersize - 0.1 (0.004) ‪

    93.880-93.900 (3.6960-3.6968) ‪

    Undersize - 0.25 (0.010) ‪

    93.730-93.750 (3.6901-3.6909) ‪

    Undersize - 0.50 (0.020) ‪

    93.480-93.500 (3.6803-3.6811) ‪

    Undersize - 0.75 (0.030) ‪

    93.230-93.250 (3.6705-3.6712) ‪

    Undersize - 1.00 (0.040) ‪

    92.980-93.000 (3.6606-3.6614) ‪

    Bearing Journal Specifications
    1. Measure the bearing journal in the vertical plane and note the reading.
    2. Measure the bearing journal in the horizontal plane and note the reading.
    3. Calculate the average (nominal) bearing-journal diameter from these two measurements, and determine the current repair stage listed in Table .

      Repair Stage: mm (in.)

      Diameter: mm (in.)

      Standard ‪

      94.054-94.096 (3.7029-3.7046) ‪

      Undersize - 0.10 (0.004) ‪

      93.954-93.996 (3.6990-3.7006) ‪

      Undersize - 0.25 (0.010) ‪

      93.804-93.846 (3.6931-3.6947) ‪

      Undersize - 0.50 (0.020) ‪

      93.554-93.596 (3.6832-3.6848) ‪

      Undersize - 0.75 (0.030) ‪

      93.304-93.346 (3.6734-3.6750) ‪

      Undersize - 1.00 (0.040) ‪

      93.054-93.096 (3.6635-3.6652) ‪

      Bearing Bore Inside Diameter with Bearing Shells Installed

      NOTICE:

      Be sure the vise jaws in the next step are adequately lined to prevent the connecting rod surface from being nicked or marred in any way. Such surface damage could lead to later cracking or breaking of the rod.

  8. Place the connecting rod in a vise with protective jaws. To prevent the rod from twisting excessively, position the rod in the vise as close as possible to the big-end bore.
  9. Set the caliper (internal measurement 80 to 100 mm) to the nominal bearing-journal diameter calculated above. Use a 75 to 100 mm micrometer for the setting. Preload the setting 5 mm (0.2 inch). See Figure 41999 .

    Setting the Caliper

  10. Using a quick-release caliper (internal measurement 80-120 mm), dial gauge, and holder, measure the inside diameter of the bearing bore (with the shells installed) at three points. Measure vertically and about 60 degrees each side of vertical. See Figure 42000 to locate the measuring points, and find the current specifications listed in Table .

    1. Bolt ‪

    2. Bearing Cap ‪

    Measuring the Inside Diameter of the Bearing Shell

    1. Measure the bearing bore in the vertical dimension and note the reading.
    2. Mark off a point 60 degrees counterclockwise from vertical. Measure the bearing bore in this dimension and note the reading.
    3. Mark off a point 60 degrees clockwise from vertical. Measure the bearing bore in this dimension and note the reading.
    4. Calculate the average (nominal) bearing-journal diameter from these three measurements, and determine the current repair stage listed in Table .

      If any of the measurements are out of tolerance, replace the bearing shells. ‪

      Note: Connecting-rod bearings for all repair stages are delivered from the factory ready to install. Do not refinish them in any way.

      Note: To obtain a correct value for connecting-rod radial play, the diameters of each bearing bore and its corresponding journal must belong to the same repair stage (both must be "standard," "undersize 0.1 mm," etc.).

  11. Calculate the connecting rod radial play (up-and-down movement) at the bearing journal. If the radial play is less than 0.054 mm (0.0021 in.), or more than 0.116 mm (0.0046 in.), replace the connecting rod. Listed in Table is the radial play.

    Description

    Dimensions: mm (inch)

    Radial Play ‪

    0.054 - 0.116 (0.0021 - 0.0046) ‪

    Connecting Rod Radial Play
    1. For each connecting rod, note the average value for the bearing bore diameter, as calculated. Example: Ds = 3.5421 inches.
    2. For each bearing journal, note the average value for the bearing journal diameter, as calculated. Example: Dj = 3.5391 inches.
    3. From the value for the bearing bore diameter, subtract the value for the bearing journal diameter. This result is the radial play. Example: Ds Dj = 0.0030 inch.

      Note: In the above example, both measurements belonged to repair stage "undersize 0.1 mm."

  12. Remove the bearing cap from the connecting rod.
  13. Install the piston. Refer to section .

Connecting Rod Bushing Replacement

Replace the connecting rod bushing as follows: ‪

NOTICE:

Be careful to avoid damaging the bushing bore when removing the bushing. A damaged connecting rod can seize up suddenly, causing major engine repairs.

  1. Rest the connecting rod on a flat surface. Using an appropriate drift, press the bushing out of the connecting rod. See Figure 42001 .

    1. Bushing ‪

    2. Connecting Rod ‪

    Remove the Bushing

  2. Check the bushing bore in the connecting rod. If surface material is missing from the bushing bore, replace the connecting rod.
  3. Measure the inside diameter of the bushing bore in the small bore of the connecting rod. If the measurement exceeds 57.019 mm (2.2448 in.), replace the connecting rod. Refer to section .

    Note: The inside diameter of the bushing bore and the outside diameter of the bushing must conform to the specifications listed in Table . This is necessary to obtain the required interference fit.

    Description

    Dimensions: mm (in.)

    Inside Diameter of Bushing ‪

    52.05-52.07 (2.049-2.050) ‪

    Outside Diameter of Bushing ‪

    57.080-57.100 (2.2472-2.2480) ‪

    Inside Diameter of Bushing Bore ‪

    57.000-57.019 (2.2441-2.2448) ‪

    Bushing Interference Fit ‪

    0.061-0.100 (0.0024-0.0039) ‪

    Maximum Permissible Out-of-Round in Bushing Bore ‪

    0.01 (0.0004) ‪

    Bushing Specifications
  4. Measure the outside diameter of the bushing. If the measurement exceeds 57.100 mm (2.2480 in.), replace the bushing.
  5. Measure the bushing bore in the connecting rod for deformation. If the bushing bore is out-or-round by more than 0.01 mm (0.0004 in.), replace the connecting rod.
  6. Rest the connecting rod on a flat surface. Using an appropriate drift, install the bushing in the connecting rod.
  7. Measure the inside diameter of the bushing. If the measurement is shorter than 52.05 mm (2.049 in.), machine the inside contact surface of the bushing until the measurement is correct.