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Checking valve guides > < Camshafts: checking axial clearance

Leon Mk2

Machining valve seats
Machining valve seats
Special tools and workshop equipment required
   
t  Ruler -T40100-
t  Gauge
t  Valve seat refacing tool
  Note
t  When repairing engines with leaking valves, it is not sufficient to rework or renew valve seats and valves. The valve guides must also be checked for wear. This is particularly important on high mileage engines → Chapter.
t  Valve seats are only to be reworked to the extent required to yield a proper surface appearance. Before beginning to rework valve seats, calculate the maximum permissible reworking dimensions. If the reworking dimension is exceeded, hydraulic valve compensation can no longer be guaranteed and the cylinder head should be renewed.
Calculate the maximum permissible reworking level as follows:
–  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.
  W00-10297
–  Measure distance between end of valve stem and upper edge of the measuring guage -T40100-.
–  Calculate maximum permissible machining dimension from measured distance and minimum dimension.
Highest dimension: Inlet valve 1.0 mm, Outlet valve 0.9 mm
Maximum dimension minus measured distance of the valve protrusion = max. permissible reworking dimension.
  Note
Material thickness measuring ruler -T40100- = 7.7 mm.
Example for intake valve:
   Material thickness -T40100- - measured protrusion = valve protrusion dimension
   7.7 mm - 7.2 mm = 0.5 mm
   Maximum inlet valve dimension - valve protrusion = max. permissible machining dimension.
   1.0 mm - 0.5 mm = 0.5 mm → Remark
Max. permissible reworking dimension of the inlet valve = 0.5 mm
1)  The max. permissible reworking dimension is shown as dimension „b“ in the illustrations for reworking valve seats.
  N15-10641
Reworking inlet valve seat
  N15-0096
a
b
c
Z
α
β
γ		= Ø 34.8 mm
= maximum permitted reworking dimension1
= 1.3 - 1.9 mm
= cylinder head lower edge
= 45° valve seat angle
= 30° upper correction angle
= 70° lower correction angle

2)  Calculating max. permissible reworking dimension → Chapter.
Reworking exhaust valve seat
   
a
b
c
Z
α
β
γ		= Ø 29.0 mm
= maximum permitted reworking dimension1
= 1.9 - 2.0 mm
= cylinder head lower edge
= 45° valve seat angle
= 30° upper correction angle
= 70° lower correction angle

3)  Calculating max. permissible reworking dimension → Chapter.
   

Checking valve guides > < Camshafts: checking axial clearance