Valve Seat, Refacing

WARNING: This page is about a different car, the 2008 Volkswagen R32. However, it is still accessible from the selected car via links, so may be relevant.

Special tools and workshop equipment required

Depth gauge
Valve seat refacing tool

Procedure

NOTE:

When repairing engines with leaking valves, it is not sufficient to reface or replace the valve seats and valves. It is also necessary to check the valve guides for wear. This is particularly important on high mileage engines. Refer to VALVE GUIDES, CHECKING .

Only reface the valve seats enough until a perfect contact pattern is obtained. The maximum permissible refacing dimension must be calculated before the work is performed. If the refacing dimension is exceeded, the function of the hydraulic lifters can no longer be guaranteed and therefore the cylinder head should be replaced.

-- Remove the camshafts. Refer to CAMSHAFTS .

Maximum Permitted Refacing Dimension is Calculated as Follows:

-- Insert the valve and press it firmly against the seat.

NOTE:

If the valve is to be replaced as part of a repair, use a new valve for the calculation.

-- Measure the distance -a- between the end of the valve stem and the upper edge of cylinder head.

Fig 1: Identifying Distance Between End Of Valve Stem And Upper Edge Of Cylinder Head

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Calculate the Max. permissible refacing dimension from the measured distance -a- and minimum dimension.

Minimum Dimensions

Short intake valve	mm	31.8
Long intake valve	mm	10.2
Short exhaust valve	mm	31.8
Long exhaust valve	mm	10.2

Measured the distance -a- minus the minimum dimension = Max. permissible reface dimension.

Example

	Measured distance	10.6 mm
-	Minimum dimension	10.2 mm
=	Max. permissible refacing dimension*	0.4 mm

Intake Valve Seat Refacing

Fig 2: Identifying Angles And Dimensions To Rework Exhaust Valve Seat

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

a = Diameter 32.8 mm

b = Max. permissible refacing dimension*

c = 0.9 to 1.5 mm

d = Max. diameter 38.0 mm

r2 = Radius 2.0 mm

Z = Cylinder head lower edge

α - 45° valve seat angle

β - 30° upper correction angle

γ - 60° lower correction angle

Exhaust Valve Seat Refacing

Fig 3: Identifying Angles And Dimensions To Rework Exhaust Valve Seat

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

a = Diameter 29.8 mm

b = Max. permissible reworking dimension*

c = 1.2 to 1.7 mm

d = Max. diameter 35.0 mm

r2 = Radius 2.0 mm

Z = Cylinder head lower edge

α - 45° valve seat angle

β - 30° upper correction angle

γ - 60° lower correction angle