Valve seats, refacing
WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
If a perfect contact pattern is not created after hand-lapping valve seats, reface valve seats.
Special tools and equipment
- Depth gauge
- Valve seat refacing tool
NOTE:
- When servicing engines with leaking valves, refacing or replacing valve seats and valves is not sufficient. It is particularly important to check valve guides for wear on engines with higher running performance. Refer to Valve guides, checking .
- Only reface valve seats enough until a perfect contact pattern is obtained.
- Before refacing, determine maximum refacing dimension.
- If refaced dimension is exceeded, hydraulic valve lifter function is no longer guaranteed and cylinder head must be replaced.
Determining maximum allowable refacing dimension
- Insert valve and press tightly against valve seat.
NOTE:
If valve is replaced during repair, use new valve for measurement.
Fig 1: Measuring Distance Between Valve Stem End (Upper Edge) And Top Surface Of Cylinder Head Using Depth Gauge
- Measure distance -a- between valve stem end (upper edge) and upper cylinder head surface using a depth gauge.
- Determine maximum allowable refacing dimension using distance measured and minimum dimension.
| Minimum dimensions | ||
| Outer intake valves | Center intake valve | Exhaust valves |
| 31.0 mm | 32.2 mm | 31.9 mm |
Measured distance minus minimum dimension = max. permissible refaced dimension.
| Example for outer intake valve: | |||
| Distance measured | 31.4 mm | ||
| - | Minimum dimension | - 31.0 mm | |
| = | Maximum allowable refaced dimension | = 0.4 mm | |
NOTE:
If the maximum allowed refaced dimension is 0 mm or less than 0 mm, repeat measurement using new valve. If measurement result is still 0 mm or less than 0 mm, replace cylinder head.
Valve seats, refacing
| Dimension | Intake valve seat | ||
| Dia.a | mm | 26.2 | |
| b | mm | 1.5 to 1.8 | |
| Z | Lower edge of cylinder head | ||
| α | 45° | Valve seat angle | |
| β | 30° | Upper correction angle | |
| γ | 60° | Lower correction angle | |
| Dimension | Exhaust valve seat | |
| Dia.a | mm | 29.0 |
| b | mm | 1.8 |
| Z | Lower edge of cylinder head | |
| α | 45° | Valve seat angle |
| β | 30° | Upper correction angle |
| γ | 60° | Lower correction angle |