Valve Seats, Reworking

WARNING: This page is about a different car, the 2015 Volkswagen Jetta. 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

NOTE:

Cylinder heads with cracks between the valve seats, or between the valve seat and the spark plug threads, can continue to be used without reducing the service life, as long as the cracks have a width of max. 0.3 mm, or only the first 4 threads of the spark plug threads are cracked.

After installing new hydraulic valve lifters, the engine may not be started for approximately 30 minutes. Otherwise the valves will impact the pistons.

Turn over the engine carefully at least two turns after working on the valvetrain. This assures the valve do not strike the piston when starting the engine.

Perform the Following Work

NOTE:

When repairing engines with leaking valves, it is not sufficient to rework or replace valve seats and valves. It is particularly important to check valve guides for wear on engines with longer running times.

Only reface valve seats enough until a perfect contact pattern is obtained. The maximum permissible reworking dimension must be calculated before work is carried out. If the reworking dimension is exceeded, the function of the hydraulic lifters can no longer be guaranteed. Then replace the cylinder head.

Calculate the Maximum Reworking Dimension

-- Insert valve and press firmly against seat.

NOTE:

If the valve was replaced during a repair, a new valve must be used to measure.

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

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Calculate maximum permissible reworking dimension from measured distance -a- and minimum dimension.

Minimum Dimensions

Intake valve: 33.8 mm

Exhaust valve: 34.1 mm

Measured distance -a- minus minimum dimension

= Max. permissible reworking dimension

Example

Measured distance -a-

35.1

Minimum dimension

34.1

maximum permitted reworking dimension ⁽¹⁾

1.0

⁽¹⁾	Maximum allowable refacing dimension is represented in illustrations for refacing valve seats as dimension "b".

Reworking Intake Valve Seat

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

Dimension		Intake Valve Seat
Diameter a	mm	39.2
b	mm	Maximum permissible reworking dimension
c	mm	1.8 to 2.2
Z		Cylinder Head Lower Edge
45°		Valve seat angle
30°		Upper correction angle

Reworking Exhaust Valve Seat

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

Dimension		Exhaust Valve Seat
Diameter a	mm	32.4
b	mm	Maximum permissible reworking dimension
c	mm	2.2 to 2.6
Z		Cylinder Head Lower Edge
45°		Valve seat angle
30°		Upper correction angle