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Renewing camshaft oil seal > < Repairing valve gear

Golf Mk4

Reworking valve seats
Reworking valve seats
Special tools and workshop equipment required
t  Depth gauge
t  Valve seat refacing tool
  Note
t  When repairing engines with leaking valves, it is not sufficient to reface or renew valve seats and valves. Particularly on high mileage engines, it is necessary also to check valve guides for wear → Chapter.
t  Valve seats should be reworked only enough to produce a perfect seating pattern. Before beginning to rework valve seats, calculate the maximum permissible reworking dimension. If the reworking dimension is exceeded, hydraulic valve compensation can no longer be guaranteed and the cylinder head should be renewed.
Calculating the maximum permissible rework dimension:
–  Insert valve and press firmly against seat.
  Note
If the valve is to be renewed as part of a repair, use a new valve for the calculation.
   
–  Measure distance -a- between end of valve stem and upper edge of cylinder head -1-.
–  Calculate maximum permissible reworking dimension from measured distance and minimum dimension.
Minimum dimension: outer inlet valve: 31.0 mm, centre inlet valve: 32.3 mm, exhaust valve: 31.9 mm.
Measured distance minus minimum dimension = max. permissible reworking dimension.
Example:
  N15-0438
Measured distance31.4 mm
Minimum dimension31.0 mm
max. perm. rework dimension → Note0.4 mm

1)  The max. permissible reworking dimension is shown on illustrations for reworking valve seats as dimension “b”.
   
Reworking inlet valve seat
a = Ø 26.2
b = max. permissible reworking dimension → Note
c = 1.5...1.8 mm
Z = cylinder head lower edge
α = 45 ° valve seat angle
β = 30 ° upper correction angle
γ = 60 ° lower correction angle
2)  Calculating max. permissible reworking dimension → Chapter.
  N15-0096
Reworking exhaust valve
a = Ø 29.0
b = max. permissible reworking dimension → Note
c = approx. 1.8 mm
Z = cylinder head lower edge
α = 45 ° valve seat angle
β = 30 ° upper correction angle
γ = 60 ° lower correction angle
3)  Calculating max. permissible reworking dimension → Chapter.
  N15-0096

Renewing camshaft oil seal > < Repairing valve gear