Audi Workshop Service and Repair Manuals

Note:

Rework valve seats if grinding-in does not yield proper surface appearance.

Special tools and workshop equipment required

• ◆ Depth gauge
• ◆ Valve seat grinding tool

Notes:

• ◆ When repairing engines with leaking valves, it is not sufficient to reface valve seats and renew valve. Particularly in the case of high-mileage engines, it is necessary to check the valve guides for wear => Page 15-85.
• ◆ Valve seats should only be reworked just enough to produce a perfect seating pattern.
• ◆ Calculate the maximum permissible reworking dimension before reworking.
• ◆ If max. perm. reworking dimension is 0 mm or less than 0 mm, repeat measurement with new valve. Replace cylinder head if result obtained is still 0 mm or less than 0 mm.

Calculating max. perm. reworking dimension

• ‒ Insert valve and press it firmly against valve seat.

Note:

Use new valve for measurement purposes if valve is replaced as part of repair work.

• ‒ → Use depth gauge to measure distance -a- between end of valve stem (upper edge) and upper surface of cylinder head.
• ‒ Calculate max. perm. reworking dimension from distance measured and minimum dimension.

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

Note:

If max. perm. reworking dimension is 0 mm or less than 0 mm, repeat measurement with new valve. Replace cylinder head if result obtained is still 0 mm or less than 0 mm.

→ Reworking inlet valve seat

Note:

The 30 ° relief-milling of the valve seat is essential because of the flow conditions in the intake duct.

→ Reworking exhaust valve seat