Timing Components: Service and Repair

Cylinder Head and Valve Drive, Component Layout

NOTE: Cylinder heads with cracks between valve seats or between valve seats and spark plug threads can be used again without reducing service life, provided that the cracks are not wider than 0.5 mm.





1 - Bearing cap
- Installation position Fig. 2 below.
- Installation sequence see below.

2 - 20 Nm (15ft lb)

3 - Camshafts
- Checking axial clearance see Fig. 1 below.
- Removing and installing refer to Camshaft, removing and instaling.
- Radial clearance, checking with Plastigage�

Wear limit: 0-01 mm
Max. runout: 0.001 mm

4 - Camshaft sprocket
- Removing and installing refer to Camshaft, removing and installing.

5 - Trigger wheel
- For Camshaft position Sensor (G40)
- When installing, contact surfaces on timing chain and trigger wheel must be dry.
- Removing and installing refer to Camshaft removing and installing.

6 - 100 Nm (74 ft lb)
- When removing or installing, counter-hold with 24 mm open wrench on camshaft refer to Camshafts, removing and installing.
- Oil bolt head contact surfaces when installing.

7 - Clutch for ignition distributor
- Not for electronic ignition system

8 - Cylinder head minimum height
Minimum height: 139.5 mm

9 - Cylinder head
- See note above.
- Do not reface valve seats, only lapping permitted.

10 - Valves
- Do not reface, only lapping is permitted.
- Valve dimensions see Fig. 3 below.

11 - Valve guide
- Service version with collar.

12 - Valve stem seal

13 - Valve springs
- Removing and installing:
with cylinder head removed use 2037.
with cylinder head installed: refer to "Valve Stem Seals, Replacing". Service and Repair

14 - Valve spring plate

15 - Valve keepers

16 - Hydraulic lifter
- Do not mix up.
- Store with cam contact side downward.
- Before installing check camshaft axial clearance Fig. 1
- Oil contact surfaces.

Camshaft Axial Clearance, Checking





Wear limit: 0.15 mm

Check with hydraulic lifters removed. First and last bearing caps must be installed for applicable camshaft

Camshaft Bearing Caps, Installed Position





You must be able to read bearing cap identifications from the exhaust side of cylinder head with arrow pointing to vibration damper end of engine.

Valve Dimensions

Fig. 3:

NOTE: Do not grind valves. Only lapping is permitted.

Valve Seats, Refacing

NOTE:
When repairing an engine with leaking valves be sure to also check valve guides for wear. This is especially important for high mileage cars.

Only reface valves to get a perfect seat. Calculate the maximum permissible dimension before you start with the repair. If the reworking dimension is exceeded, the functioning of the hydraulic valve lifters cannot be assured. In such case replace the cylinder head.

Maximum Permissible Refacing Dimension Calculating

- Insert valve and press firmly against seat.

NOTE: If you plan to replace the valve use a new valve for the calculation.





- Measure distance -a- between end of valve stem and upper edge of cylinder head.

- Calculate maximum permissible reworking dimension from measured distance -a- and minimum dimension.

Minimum dimension:
Intake valve: 33.9 mm
Exhaust valve: 34.1 mm

Measured distance minus minimum dimension = maximum permissible reworking dimension.

Example:

Valve Seat, Refacing

Intake Valve:

Exhaust Valve: