Cylinder heads — removal and installation (Mercedes-Benz S-Class W140)

Removal

Attention! Removal of cylinder heads with camshafts and exhaust manifolds is possible only after the engine has completely cooled down!

1. Set the piston of the first cylinder to the position 30° after TDC. In this position, the camshafts can be turned without the valves and pistons colliding.



2. Mark the relative positions of the camshaft sprockets relative to the timing chain.



3. On the left cylinder head: remove the crankcase ventilation tube (5).





4. On the left cylinder head, remove the guide arm pin (1) using a puller and a threaded insert.



5. Unscrew the exhaust air mixing pump filter and remove it.

6. Remove the air supply tubes from the exhaust air mixing pump. On the right cylinder head, there is one bolt on the head, one bolt on the engine bracket, and one bolt on the engine oil pan. On the left cylinder head, there is one bolt on the head, one on the cylinder block below the exhaust manifold, and one on the left engine bracket.

7. Unscrew the oil level indicator guide pipe. On the right cylinder head, unscrew the ATF dipstick guide pipe (7) from the cylinder block and transmission.

8. On the right cylinder head, also unscrew the crankcase ventilation tube (8) from the cylinder head (arrow).





9. Unscrew the exhaust manifold at the rear of the cylinder block.



10. Drain the coolant from the cylinder block. To do this, unscrew the plugs (arrow) with seals. Tightening torque 30 Nm.



11. Following the reverse order to that shown in the illustration, loosen the cylinder head bolts in the reverse order of tightening, starting with bolt 14.





12. Install the lifting eye on the cylinder head. Unscrew the cover of the 1st bearing of the exhaust camshaft on the right cylinder head and install the bracket with guide bushings (18a). Unscrew the cover of the 2nd bearing of the exhaust camshaft on the left cylinder head and install the bracket with guide bushings (18a). Tightening torque 21 Nm.



13. Attach the hoist to the bracket and the rear engine lifting point, lift and remove the cylinder head.

Caution! Do not damage the tension and guide levers!

14. Check the contact surface of the cylinder head.

Installation

1. Install the gasket. Pay attention to the position of the guide pins (1) and guide bushings (2) for the cylinder head position.



2. Check the cylinder head mounting bolts.



3. Lubricate the threaded portion of the bolts and the contact surfaces of the cylinder heads with engine oil and insert them.

4. Tighten the mounting bolts in a strictly defined order.



5. Further installation is carried out in the reverse order of removal. Check the installation of the camshafts. Check the fluid level in the AT and top it up if necessary.