Cylinder head (2.2/2.5L engine) (Mercedes-Benz C-Class W202)

Cylinder head bolts (2.5L engine)

Note! The illustration applies to a 2.5L engine (22 bolts). For a 2.2L engine with 18 bolts in the cylinder head, the sequence of actions is the same.

The cylinder head is disassembled only on a cooled engine. The outlet and intake pipe branches remain connected. The signs of a defective cylinder head gasket are the same as described for the 2 liter engine.

Removal

1. Lift the engine hood.

2. Disconnect the battery ground (–) cable.

Attention! This will erase the radio's anti-theft code.

3. Raise the vehicle from the front and remove the lower engine compartment cover.

4. Drain the coolant.

5. Unscrew the front exhaust pipe from the exhaust manifold.

6. Unscrew the exhaust pipe from the side bracket.

7. Unscrew the fan hydraulic coupling.

8. Loosen and remove the V-ribbed belt.



9. Disconnect the vacuum hoses (2, 3) from the vacuum pump (5) and the distributor part (arrow). If necessary, first loosen and move back the hose clamps.



10. Remove the cooling system air bleed hose (1) and the coolant hose, after loosening the hose clamps.

11. Remove the hose connecting the air filter.



12. Disconnect the vacuum hoses (7) and (8) from the vacuum tank, the pressure regulator valve and the outlet device recirculation valve.

13. Disconnect the wires from the temperature switches on the left side of the cylinder head and the cooling system flange.

14. Remove the camshafts.



15. Remove the upper pins (14) of the steering chain guide bar (15) using a puller (2) and an M6 pin. If such a tool is not available, the pins can be removed using a ten-tooth chain sprocket (square length = 1/2 inch) and an M6 bolt, which is approximately three times the length of the sprocket, and a lock nut. To do this, screw the lock nut onto the M6 bolt and insert a spacer washer on top of the bolt. Place the sprocket on the pin, screw the M6 bolt into the pin thread and tighten the lock nut until it touches the surface of the sprocket. The spacer washer serves to improve surface contact. Pull out the pin while holding the bolt head with a wrench and simultaneously turning the lock nut with a wrench relative to the sprocket.



16. Also remove the lower pins of the guide rail located below the coolant connection element.



17. Unscrew the camshaft housing (10) and remove it. There is no need to remove the plate tappets: they will not fall out, thanks to the lower projections.

Caution! Pay attention to the two mounting sleeves (13). The O-ring (12) must be replaced with a new one when re-installing.

18. Remove the injectors with fuel lines.



19. Unscrew the oil level dipstick guide tube (10) for the automatic transmission (if there is one) from the cylinder head at the back right.

20. Unscrew the oil dipstick guide tube (11) from the cylinder head.

21. Unscrew the shock absorber (13) of the ribbed V-belt tensioner from the cylinder head.





22. Disconnect the fuel lines (90/1) and (90/2) from the fuel preheater.

Attention! To facilitate subsequent installation, mark the fuel lines with adhesive tape. Collect spilled fuel with a rag.

23. Disconnect the cable channel (22) from the fuel preheating device.



24. Unscrew the electrical wires from the glow plugs (R9), having previously marked the wires with adhesive tape.

25. Disconnect the plug connections from the coolant temperature sensor for the air conditioner (B10/8), the indicator instrument (B11/4) and the glow plug (B11/8).

26. Unscrew the cable channel (1) from the fuel heat exchanger (60).

27. Disconnect the thick coolant hose from the rear of the cylinder head by fully opening the retaining clamp.



28. Unscrew the mounting bolts, remove the fuel filter with the holder from the cylinder head and put it aside together with the connected fuel lines.

29. Remove the guide bar in the chain case in the same manner as the top bar.



30. Remove the two M8 cylinder head bolts using a long SW socket wrench.

31. Unscrew the cylinder head bolts in the reverse order of their numbering, i.e. from 22 to 1 (see Fig. Cylinder head bolts (2.5L engine)). In this case, first loosen all the bolts by 1/2 turn, and then completely unscrew them using a socket wrench, for example, HAZET 2751.

32. It is better to lift the cylinder head with two people. In repair shops, they screw on the holder (17) instead of the outer cover of the camshaft bearing and hang a pulley block to lift the cylinder head.

Installation

1. Before installing, scrape off any remaining sealant from the cylinder head. Make sure that it does not get into the holes.



2. Blow the threaded holes clean of oil and water with compressed air. If there is no compressed air, soak up the liquid in the blind holes with a rag wrapped around a small screwdriver.

3. Check the cylinder head and cylinder block for cracks and flatness using a steel ruler.

4. Be sure to replace the cylinder head gasket (20).

5. Apply a new gasket without sealant so that it does not cover the holes.

6. Install the cylinder head (21).

Caution! Center the cylinder head using the locking sleeves (19) on the engine block.

7. Measure the length (L) of the cylinder head bolts. If the maximum length is exceeded (see table Cylinder Head Bolts), then replace the bolt just in case.

8. Lubricate the threads of the cylinder head bolts and the area where they fit with engine oil, screw in the bolts and tighten by hand (see Fig. Cylinder head bolts (2.5L engine)).

Caution! Cylinder head bolts are installed without spacer washers. Tighten the cylinder head bolts carefully. Check the accuracy of the torque wrench beforehand.

Tighten the cylinder head bolts in sequence from 1 to 22 and, respectively, from 1 to 18, in 4 stages.

Attention! The cylinder head bolts are tightened at each stage in sequence from 1 to 22 or from 1 to 18.

• Step 1: Using a torque wrench with a torque of 15 Nm.
• Stage 2: using a torque wrench with a torque of 35 Nm.
• Step 3: Using an open-end wrench, tighten the bolts in the same direction by 90°. Pause for a minute to allow the bolts to settle. Then tighten the bolts further without loosening them.
• Step 4: Turn the bolts in the same direction by 90° with an open-end wrench.

Caution! When tightening bolts, evaluate the rotation angle. Place the wrench handle along the engine and tighten the bolt with one force until the wrench handle is across the engine (1/4 turn, 90°).

9. Install 2 M8 bolts (a) at the front of the cylinder head with spring washers and tighten with a long socket wrench SW6 to a torque of 25 Nm.

10. Install the fuel filter with the holder and tighten the bolts (b) to a torque of 25 Nm.



11. Install the lower guide bar of the timing chain in the chain case and insert the stop pins. At the same time, install the guide bar so that the installation parts of the upper stop pin (A) and the lower pin (B) are on top.



12. Place the thick coolant hose onto the rear coolant pipe and secure it with a clamp.

13. Connect the electrical wires to the glow plugs and coolant temperature sensors.

14. Screw the cable channel to the fuel preheating system.

15. Connect the V-ribbed belt tensioner shock absorber to the cylinder head with a torque of 25 Nm.

16. Screw the dipstick guide tube in the engine and in the automatic transmission to the cylinder head.

17. Install the injectors.



18. Install the camshaft housing with plate tappets and center with two relief bushings (13).

Caution! The O-rings (12) between the cylinder head and the camshaft housing must always be replaced with new ones. Tighten the two bolts (11) to a torque of 15 Nm.

19. Install the upper guide rail of the control chain, drive in the stop pins.

20. Install the camshafts and cylinder head cover.

21. Install the air filter hose.

22. Attach 2 vacuum hoses to the vacuum tank of the pressure regulator valve and the exhaust gas recirculation valve.

23. Place the wire on the temperature switch on the left side of the cylinder head onto the coolant flange.



24. Place the vacuum hoses (2, 3) on the vacuum pump (5) and the distributor part (arrow), secure the hoses with clamps.

25. Fit the coolant deaeration hose (1) and coolant hose (4) and secure with clamps.

26. Install the ribbed V-belt.

27. Attach and adjust the throttle control cable.

28. Install the fan hydraulic clutch.

29. Bolt the front exhaust pipe to the manifold and side brackets.

30. Fill with coolant.

31. Connect the ground (–) cable to the battery.

Attention! If the cylinder head gasket was defective, the engine oil and oil filter should be replaced.

32. Bring the engine to operating temperature and check the tightness of all connecting elements.

33. Install the lower engine compartment cover and tighten the bolts.

Caution! Tightening the cylinder head bolts is prohibited.

34. To close the engine hood, press the release button on the left bracket.

Cylinder head bolts

Thread diameter	Length in new position	Maximum length
M 10	102.0 mm	104.0 mm
M 10	115.0 mm	117.0 mm