Section 12.1 Valve Lash Checking

Section 12.1
Valve Lash Checking

Check and adjust the valve lash as follows:‪

Note: Adjust the valve lash when the engine is cold. Wait at least 30 minutes after shutdown, even if the engine ran only a short time.

Select a method for adjusting the valves. There are two acceptable methods for adjusting the valves, prior to checking the valve lash:‪

  • In order, according to the timing sequence used for fuel injection (see Method One—Adjust Each Cylinder in Firing Order);
  • By type of valve, depending on crankshaft position (see Method Two—Adjust All Valves Using Two Crankshaft Positions).

    See Figure "Cylinder and Valve Layout" for the cylinder and valve layout on MBE 4000 engines.‪

    Click to see this graphic in a separate window

    Figure 1. Cylinder and Valve Layout

Section 12.1.1
Method One — Adjust Each Cylinder in Firing Order

Method one allows you to adjust each cylinder in the order in which fuel is injected. The crankshaft must be repositioned after each cylinder is adjusted as listed in Table "Valve Adjustment (Method One)" .‪

Engine

Crankshaft Position

Cylinders

Cylinders

Cylinders

Cylinders

Cylinders

Cylinders

MBE 4000‪

Ignition TDC‪

1‪

5‪

3‪

6‪

2‪

4‪

MBE 4000‪

Valve Overlap‪

6‪

2‪

4‪

1‪

5‪

3‪

Table 1. Valve Adjustment (Method One)

Note: Clean each cylinder head cover before removing it.

  1. Remove the cylinder head covers. See Figure "Cylinder Head Cover, (exploded view)" .
    Click to see this graphic in a separate window

     1. Socket-Head Bolt‪

     3. Gasket‪

     2. Cylinder Head Cover‪

     4. Cylinder Head‪

    Figure 2. Cylinder Head Cover, (exploded view)

  2. Remove the inspection cover on theflywheel housing.
  3. Fit the engine cranking tool (J 46392) into the inspection hole on the flywheel housing. See Figure "Placement of Engine Cranking Tool" .
    Click to see this graphic in a separate window

     1. Inspection Cover‪

    Figure 3. Placement of Engine Cranking Tool

  4. For each cylinder, use the cranking tool (J 46392) to turn over the crankshaft until the piston is exactly at top dead center (TDC) in the compression stroke. The valves must be closed and it must be possible to turn the pushrods without effort.

    Note: When the piston in cylinder #1 is at ignition TDC, the valves of cylinder #6 will overlap, meaning that both intake and exhaust valves are partially open, and show no measurable play when tested with a feeler gauge.

  5. Check each valve and adjust it (if necessary), using the procedures under the heading "Adjusting Valve Lash."
  6. For each valve, measure the valve lash with a feeler gauge between the rocker arm and valve bridge. It should be possible to pull the feeler gauge through with no more than light resistance.
  7. If the value measured is within the range given in the "Check For" column listed in Table "Valve Lash Checking and Adjustment" , check the next valve.

    Valve Type

    Check For: mm (in.)

    Adjust to: mm (in.)

    Intake‪

    0.30 to 0.60 (0.012 to 0.024)‪

    0.40 (0.016)‪

    Exhaust‪

    0.50 to 0.80 (0.020 to 0.032)‪

    0.60 (0.024)‪

    Table 4. Valve Lash Checking and Adjustment

    If the value measured is outside the range given in the "Check For" column listed in Table "Valve Lash Checking and Adjustment" , adjust the valve lash.‪

Section 12.1.2
Method Two — Adjust All Valves Using Two Crankshaft Positions

Method two allows you to adjust all the valves using just two crankshaft positions.‪

Note: Clean each cylinder head cover before removing it.

  1. Remove the cylinder head covers. See Figure "Cylinder Head Cover, (exploded view)" .
    Click to see this graphic in a separate window

     1. Socket-Head Bolt‪

     3. Gasket‪

     2. Cylinder Head Cover‪

     4. Cylinder Head‪

    Figure 4. Cylinder Head Cover, (exploded view)

  2. Remove the inspection cover on the flywheel housing.
  3. Fit the engine cranking tool (J 46392) into the inspection hole on the flywheel housing. See Figure "Placement of Engine Cranking Tool" .
    Click to see this graphic in a separate window

     1. Inspection Cover‪

    Figure 5. Placement of Engine Cranking Tool

  4. Using the cranking tool (J 46392) , turn the crankshaft until cylinder #1 is at the ignition TDC position (all valves are closed) and cylinder #6 is at the valve overlap position (all valves are open).

    Note: When the piston in cylinder #1 or #6 is at ignition TDC, there will be a small bevelled alignment mark visible through the inspection hole. See Figure "Flywheel Alignment Mark" .

    Click to see this graphic in a separate window

    Figure 6. Flywheel Alignment Mark

  5. Check the valves in the "Ignition TDC" row listed in Table "Valve Adjustment (Method Two)" , and adjust them (if necessary), using the procedures under the headings "Checking Valve Lash" and "Adjusting Valve Lash."

    Engine

    Cylinder #1 Crankshaft Position

    Cylinder Valves/Types*

    Cylinder Valves/Types*

    Cylinder Valves/Types*

    Cylinder Valves/Types*

    Cylinder Valves/Types*

    Cylinder Valves/Types*

    1‪

    2‪

    3‪

    4‪

    5‪

    6‪

    MBE 4000‪

    Ignition TDC‪

    I/E‪

    I‪

    E‪

    I‪

    E‪

    —‪

    MBE 4000‪

    Valve Overlap‪

    —‪

    E‪

    I‪

    E‪

    I‪

    I/E‪

    Table 7. Valve Adjustment (Method Two)

    * I= Intake Valve and E= Exhaust Valve
  6. Using the cranking tool (J 46392) , turn the crankshaft until cylinder #6 is at the ignition TDC position (all valves are closed) and cylinder #1 is at the valve overlap position (all valves are open).
  7. Using the same procedure, check the valves in the "Valve Overlap" row listed in Table "Valve Adjustment (Method Two)" and adjust them (if necessary), using the procedures under the headings "Checking Valve Lash" and "Adjusting Valve Lash."
  8. For each valve, measure the valve lash with a feeler gauge between the rocker arm and valve bridge. It should be possible to pull the feeler gauge through with no more than light resistance.
  9. If the value measured is within the range listed in Table "Valve Lash Checking and Adjustment" in the "Check For" column, check the next valve.

    Valve Type

    Check For: mm (in.)

    Adjust to: mm (in.)

    Intake‪

    0.30 to 0.60 (0.012 to 0.024)‪

    0.40 (0.016)‪

    Exhaust‪

    0.50 to 0.80 (0.020 to 0.032)‪

    0.60 (0.024)‪

    Table 8. Valve Lash Checking and Adjustment
  10. If the value measured is outside the range given in the "Check For" column listed in Table "Valve Lash Checking and Adjustment" , adjust the valve lash.‪


MBE 4000 Service Manual - 6SE412
Generated on 10-13-2008