Audi Workshop Service and Repair Manuals

Note:

If a good seating pattern cannot be obtained by grinding the valve seats (lapping), they must be refaced (reworked):

Special tools and workshop equipment required

• ◆ Depth gauge
• ◆ Valve seat machining tool

Notes:

• ◆ When repairing engines with leaking valves, it is not sufficient to reface the valve seats and renew the valves. The valve guides must also be checked for wear. This is particularly important on high mileage engines => Page 15-123.
• ◆ Only rework the valve seats as far as is necessary to ensure a good seating pattern.
• ◆ Before starting to rework the valve seats, calculate the maximum permissible reworking dimension.
• ◆ If the maximum permissible reworking dimension is 0 mm or less than 0 mm, repeat the measurement with a new valve. If the measured result is again 0 mm or less than 0 mm, renew the cylinder head.

Calculating maximum permissible reworking dimension

• ‒ Insert valve and press firmly against valve seat.

Note:

If the valve must be renewed as part of a repair, use a new valve for the calculation.

• ‒ → Measure distance -a- between valve shaft end (upper edge) and upper cylinder head area with a depth gauge.
• ‒ Calculate max. permissible reworking dimension from measured distance and minimum dimension.

Measured distance minus minimum dimension
= max. permissible reworking dimension.

Note:

If the maximum permissible reworking dimension is 0 mm or less than 0 mm, repeat the measurement with a new valve. If the measured result is again 0 mm or less than 0 mm, renew the cylinder head.

→ Reworking inlet valve seat

Note:

The 30 ° angle on the valve seat is vital for the flow characteristics in the inlet duct.

→ Reworking exhaust valve seat