Valve Seat: Testing and Inspection

Valve seats, reworking

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

Special tools and equipment
^ Depth gauge
^ Valve seat machining device

Note:
^ When servicing engines where valves are leaking, it is not sufficient to machine/replace valve seats and valves. Particularly in the case of high-mileage engines, it is necessary to check the valve guides for wear.
^ Valve seats are only to be reworked to the extent required to yield a proper surface appearance.
^ The maximum permissible reworking dimension is to be calculated before starting work.
^ If reworking dimension is exceeded, proper hydraulic valve filter operation can no longer be guaranteed and cylinder head is to be replaced.

Calculating max. perm. reworking dimension
- Insert valve and press it firmly against valve seat.

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





- Measure distance -a- between end of valve stem and center axis of camshaft (center axis of camshaft is on a level with top edge of cylinder head).
- Calculate maximum permissible reworking dimension from distance measured and minimum dimension.





Minimum dimensions





Measured distance minus minimum dimension max. perm. reworking dimension

Note: If maximum permissible 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.

Part 1:

Part 2:

Reworking valve seats