Field Remedy: 2379

Remedy:

These Quick Information shall help to carry out a
correct diagnosis in case of a customer complaint.

A. Check for thermal overload:

    Through friction of clutch plate on the friction surface of
    the two-mass flywheel temperatures up to 200 °C can arise 
    during normal driving. At sliding clutch or through operating
    errors much higher temperatures can arise. These temperatures
    must not cause mandatory a reduced lifetime of the two-mass
    flywheel.

    Possible indications for a high thermal load are:

    - tarnish (bluish) as well as local hotspots on friction surface
    - tarnish (bluish) near of mounting area and riveting area of
      clutch

    If all other checkable features are well, the two-mass flywheel
    can stay in the vehicle.

    Possible indications for a too high thermal load are:

    - cracks
    - fusion zones on friction surface (material smear)
    - scores in friction surface (for example through clutch lining
      riveting at destroyed or worn clutch plate)
    - tarnish (bluish) which reaches up to bearing area of two-mass
      flywheel
    - bluish discoloration of locating pins (3 locating pins in outer
      zone of two-mass flywheel)

    In these cases the two-mass flywheel has to be replaced.

    Overview two-mass flywheel (picture I):

    1 bearing area
    2 mounting area pressure plate
    3 locating pins
    4 friction surface
    5 riveting area

    Exploded view two-mass flywheel with additional mass (picture II):

    1 secondary flywheel mass
    2 additional mass, coupled with cover and pulse-generator ring
    3 flange
    4 primary flywheel mass with bowed springs and plain bearing/
      bearing bolt
    5 toothed ring

B. Check for damaged components:

    All following checking procedures have to be carried out
    at installed two-mass flywheel. For visual check at vehicle
    very bright light and a additional bright and small pocket
    lamp is necessary. Damages like grease on primary flywheel
    and loose ore missing balance weights cannot be checked at
    installed condition. During visual check material alteration
    can be stated which eliminate a further operating suitability.

    For comparison different damages at two-mass flywheel with the
    corresponding further procedure are presented here.

 1. Inspect plain bearing for damages (picture III)

    Dependent of the manufacturer damages can be detected through
    ventilation openings of secondary flywheel. Parts of the bearing
    (1) are detached or lie loose around the bearing bolt.

    Note:
    In case of mechanical damages at plain bearing the two-mass
    flywheel has to be replaced.

 2. Inspect toothed ring for damages (picture IV)

    The toothed ring is needed to start the engine. Through
    a lot of starting procedures and/or an incorrect engaging
    starter signs of abrasion can occur on teeth of the
    toothed ring. The profile of damages can reach from only
    low signs of abrasion up to heavy material removal. The
    installation of a pulse-generator ring depends on the 
    manufacturer.

    Image IV shows signs of abrasion and mechanical damages at
    toothed ring (1), they occur through abrasion due to a lot
    of starting procedures. In this case the two-mass flywheel
    has to be replaced.

    Note:
    Light abrasion on frontal areas of teeth is allowed. If
    problems occur during starting the engine the two-mass
    flywheel has to be replaced.

 3. Inspect tilt clearance

    At two-mass flywheel the additional-mass ring looms over
    the gap between primary and secondary flywheel. It is not
    possible to carry out just a visual check.

    - Embrace two-mass flywheel and apply thumbs onto the outer
      radius of secondary flywheel
    - Apply pressure onto the secondary flywheel alternating on
      upper, lower, left and right side (picture V).

    During the tilt clearance check a functional metal rattling
    noise may occur.

      Note:
      The check must be carried out only by hand without
      any tools.

    If tilt clearance is higher than 3 mm (should be measured, do
    not make an estimation) (1, picture VI) the two-mass flywheel
    has to be replaced.

    Note:
    An absolute clear measurement is not possible with this check
    due to the different applied forces of the several workshop
    employees during the check.

 4. Inspect clearance angle

    Before the inspection of the clearance angle the two-mass
    flywheel should be rotated several times clockwise and 
    anticlockwise to receive a feeling for the resistance of
    the springs. In addition unusual loud clicking noise or
    possible rattle, crunch, grinding noise can be sounded out
    during rotating the two-mass flywheel.

    If the rotation of the flywheel is impossilbe the flywheel
    is defective and has to be replaced.

    The clearance angle is the angle (1, picture VII) about the
    secondary and the primary flywheel can be turned light against 
    each other. Thereby the flange wings (3) are moved in the duct of
    the bowed springs without adjoining the bowed springs (4). Dictated
    by functional factors the clearance angle is up to 8 teeth.

    Is the secondary flywheel rotated beyond this point the bowed
    springs in the duct are moved to spring arrestor (2) in the primary
    flywheel/cover. First now the spring force of the bowed springs
    is active.

    - Rotate secondary flywheel anticlockwise (arrow, picture VIII)
      until the elastic counterforce (spring force) is clear noticeable 
    - Release secondary flywheel slowly until the bowed springs are
      relaxed, so no counterforce acts onto the springs

    - Mark position with a vertical line by a white pencil
      on secondary flywheel (1, picture IX and X) and on
      toothed ring for starter (2, picture X)
    - Rotate secondary flywheel clockwise until the elastic 
      counterforce is clear noticeable
    - Release secondary flywheel slowly until the bowed
      springs are relaxed

    - Apply new marking on secondary flywheel (1, picture XI)
      on the heigth of the marking on the toothed ring for 
      starter (3)
    - Count amount of teeth on toothed ring for starter from
      marked tooth up to the heigth of the first marking on
      secondary flywheel(2). Dictated by functional factors
      up to 8 teeth are allowed.

    Note:
    The two-mass flywheel has to be replaced if

    - the difference exceeds the amount of 8 teeth
    - the two-mass flywheel cannot be rotated
    - during rotating the two-mass flywheel a hard metallic
      arrestor is audible or noticeable.