Valve Guide: Service and Repair

REPLACING VALVE GUIDES

1. Clean and inspect cylinder head. Cylinder heads, the valve seats or sealing surfaces of which can no longer be machined, are not suitable for replacement of valve guides.

2. Grind off enough of valve guides protruding from the camshaft end with a spot facer that guides are flush with the cylinder head.

Note: Be careful not to damage guide collar for spring retainers.





3. Place cylinder head on Special Tool 9220.





4. Loosen valve guides from the camshaft end with Special Tool 9224 by applying brief knocks and press out rest of guides toward combustion chamber end in a press.





5. Measure bores in cylinder head with an internal gauge.





6. Grind off a service valve guide, Part No. 928 104 328 52 (13.27 mm outside diameter), accordingly.
The press fit for intake and exhaust valve guides must be 0.06 to 0.08 mm.

Example: Cylinder head bore measures 13.01 mm. Service valve guide ground off to outside diameter of 13.07 to 13.09 mm.

7. Coat valve guides with talcum powder, insert with a light knock, align and press into cylinder head against stop from the camshaft end with Special Tool 9221.





Note:
- If appropriate workshop equipment is available, cool valve guides in liquid air and press into cylinder head heated to 190 °C.
- Cylinder head must not be kept in heated state (190 °C) longer than 90 minutes.

8. Correct valve guides to size 9.00 to 9.015 mm (9 H 7) with a broach.





9. If necessary, valve guides could be reamed out with Special Tool 3015.

Procedures: Always rub down valve guides with "petroleum" lube. Run out ream frequently to remove burrs. Check reamed out bore with Special Tool P 206 and, if necessary, ream out bore again with a dry ream.





10. Valve seat inserts must also be machined after replacing valve guides. Grinding in valves with grinding paste would not be sufficient.