Overhaul

Cylinder head, disassembly/assembly

Special tools:
998 6052 VALVE SPRING B21 D16 D24 998 6052 Valve Spring B21 D16 D24
999 5219 GRIP TOOL 999 5219 Grip Tool
999 5748 Valve compressor B 4164-B 6304 999 5748 Valve Compressor B 4164-B 6304
999 7012 Drift valve stem seal diesel 999 7012 Drift Valve Stem Seal Diesel

Note! The illustrations in this service information are used for different model years and / or models. Therefore there may be some variation. However, the essential information in the illustrations is always correct.

Removing tappets





Note! Magnets must not be used when lifting out the tappets.

Lift out the tappets. Mark up the tappets so that the original positions can be established.
Use a suction cup to remove the tappets.
Check for wear on the tappets.

Removing valves




Use valve spring compressor 998 6052 VALVE SPRING B21 D16 D24 998 6052 Valve Spring B21 D16 D24 with attachment claw 999 5748 Valve compressor B 4164-B 6304 999 5748 Valve Compressor B 4164-B 6304.

Remove:
- the valve locks
- the upper valve collars
- the valve springs
- the valves.

Note! Keep careful track of the position of the moving parts.

Removing valve stem seals




Use tool 999 5219 GRIP TOOL 999 5219 Grip Tool.
Remove the valve stem seals and the lower valve collars.

Clean the cylinder head:
- the gasket faces
- the combustion chambers
- the inlet and exhaust ports
- the valve seats.

Checking the cylinder head




Clean the spark plug threads (tap M14 x 1.25).
Clean the valves, valve springs and collars.
Visually check for damage.
If you are unsure, replace the cylinder head.

Checking for wear in the valve guides




Measure the wear in the valve guides. Use a dial indicator and magnetic holder. Lift the valve approximately 2-3 mm from the seat when carrying out the check.
Clearance between the valve and valve guide:
Clearance between new components: Inlet/Exhaust: 0.03 -0.06 mm.
Maximum play for used components: Inlet/Exhaust: 0.15 mm.

Installing valve stem seals





Lubricate:
- the upper end of the valve guides
- the valve stem seal.

Install:
- the lower valve spring collars
- the valve stem seal.
Press down the seal. Use tool 999 7012 Drift valve stem seal diesel 999 7012 Drift Valve Stem Seal Diesel. Press with hand force until the tool stops against the lower valve spring washer. Remove the tool.
Repeat the procedure with the remaining valve stem seals.

Installing the valve / valve springs




Lubricate the valve stem.

Install:
- the valve
- the valve spring
- the upper valve spring washer.

Caution! Do not compress more than is absolutely necessary, the valve stem seal may be damaged.

Compress the valve spring so that the three valve lock tracks are visible.
Use valve spring compressor 998 6052 VALVE SPRING B21 D16 D24 998 6052 Valve Spring B21 D16 D24 and press foot 999 5748 Valve compressor B 4164-B 6304 999 5748 Valve Compressor B 4164-B 6304. Install the valve collets. Check that valve collets are in the correct position when the spring is not loaded.
Repeat the procedure with the remaining valves.