seat Workshop Repair Guides

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Camshaft: removing and fitting > < Hydraulic tappets: checking

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Valve seats: reworking
Valve seats: reworking
t  Calculate the max. permisible reworking dimension → Anchor
t  Intake valve seat: rework → Anchor
t  Exhaust valve seat: rework → Anchor
Special tools and workshop equipment required
t  Depth gauge
t  Valve seat reworker
  Note
t  When repairing engines with non-hermetic valves, it is not enough to rework the valve seats, seat the valves or replace both of them. It is particularly important on high mileage engines to check the valve guides for wear.
t  Valve seats are only to be reworked to the extent required to yield a proper surface. Calculate the maximum permissible reworking dimension before reworking. If reworking dimension is exceeded, proper hydraulic valve lifter operation can no longer be guaranteed, so the cylinder head must be replaced.
Calculate the max. permisible reworking dimension
–  Insert valve and press firmly against valve seat.
  Note
If the valve is to be renewed as part of a repair, use a new valve for the calculation.
   
–  Measure distance between end of valve stem and upper edge of cylinder head.
–  Calculate maximum permissible reworking dimension from measured distance and minimum dimension.
  V15-0640
Minimum dimensions
Inlet valve33.8 mm
Outlet valve34.1 mm

Measured distance -a- minus minimum dimension = max. permissible reworking dimension.
   
Example:
 Measured distance -a-35.1 mm
-Minimum dimension- 34.1 mm
=Max. permissible reworking dim. → Note= 1.0 mm

1)  The max. permissible reworking dimension is shown on illustrations for reworking valve seats as dimension “b”.
  Note
If the max. reworking dimension is 0 mm or less than 0 mm, repeat the measurement with a new valve. If the measured result with a new valve is again 0 mm or less than 0 mm, replace the cylinder head.
   
Intake valve seat: rework
a - Ø 39.2 mm
b - Max. permissible reworking dim. → Note
c - 1.9 … 2.1 mm
Z - Lower edge of cylinder head
45° - Valve seating angle
30° - upper correction angle
2)  Calculating max. permissible reworking dimension → Anchor
  E15-0265
Exhaust valve seat: rework
a - Ø 32.4 mm
b - Max. permissible reworking dim. → Note
c - 2.3 … 2.5 mm
Z - Lower edge of cylinder head
45° - Valve seating angle
30° - upper correction angle
3)  Calculating max. permissible reworking dimension → Anchor
  E15-0265

Camshaft: removing and fitting > < Hydraulic tappets: checking