Accessory Drive Belts — Checking, Replacing and Adjusting (Mercedes-Benz C-Class W201)

Checking the drive belt - the basics

1. Due to their application and design, belts have a limited service life and to avoid problems, belts should be checked periodically.

2. The number of belts is determined by the number of additional systems (units) installed. The water pump, alternator, hydraulic pump for the power steering/suspension system, air conditioning compressor and air injection pump have a belt drive

3. To improve access for belt inspection, if desired, remove the viscous cooling fan and shroud as described in Chapter 3.

4. With the engine off, use your fingers (and, if necessary, a flashlight) move along the belts, checking for cracks and belt delamination. Also check for belt fraying and glaze, which gives the belt a shiny appearance. Both sides of the belts should be checked, which can be done by turning the belt. If necessary, turn the crankshaft with a wrench on the crankshaft pulley hub bolt so that the entire belt can be checked.

4 Cylinder Engines with Single Belt - Belt Replacement

5. Remove the cooling fan blades and cover as described in Chapter 3.

6. Loosen the tensioner bolt by a quarter to half a turn (if necessary, remove the plastic plug to gain access to the bolt) (see fig. 8.6).



7. Loosen the adjusting nut (counterclockwise), to move the adjuster back and remove the belt from the pulleys.



8. Route the new belt in the order shown around the pulleys, starting with the tensioner pulley (see Fig. 8.8, a-c). Make sure the belt is properly positioned on the pulleys.







9. Tighten the belt as follows.

Models with a graduated scale applied to the tensioner

10. On vehicles without power steering, turn the adjusting nut clockwise until the tensioner pointer is aligned with the 5th division of the scale (on the left side, looking at the scale at the front of the engine compartment) (see fig. 8.10).



11. On models equipped with power steering, turn the adjusting nut clockwise until the tip of the pointer is positioned between the 8 and 9 marks on the scale (on the left side, looking at the scale at the front of the engine compartment).

12. Tighten the tensioner bolt to the required torque and install the cover (where provided).

13. Install the radiator fan blades and shroud as described in Chapter 3.

Models with thick mark (and a cast triangle) on the tensioner scale

14. Turn the adjusting nut clockwise until the pointer tip aligns with the thick line (on the thicker edge of the triangle) on the scale (see fig. 8.14).



15. Tighten the tensioner bolt to the required torque and install the cover (where provided).



16. Install the radiator fan blades and shroud as described in Chapter 3.

4 Cylinder Engines with Multiple Belts - Belt Replacement

Alternator/Water Pump Drive Belt

17. If necessary, remove the shields from underneath the vehicle to improve access as described in Chapter 11.

18. Loosen the upper and lower generator mounting nuts and the adjusting lever mounting bolt to the camshaft drive chain housing (see fig. 8.18).



19. To move the alternator forward toward the engine to remove the belt from the pulleys, turn the adjusting bolt (see fig. 8.19).



20. Route the new belt around the pulleys, then turn the adjusting bolt to tension the belt so that with moderate pressure the belt can be deflected approximately 12 mm at the midpoint between the alternator and tensioner pulleys.



21. Hold the adjusting bolt in this position, then tighten the upper and lower generator mounting nuts in the following order. Then tighten the adjusting lever bolt.

22. Check the belt tension after a few minutes of engine operation, then, where provided, install the engine protection from below.

Power steering pump drive belt

23. Remove the alternator belt as described earlier in this paragraph.

24. Working from the opposite side of the power steering pump mounting bracket, loosen the governor mounting bolt furthest from the engine and the two mounting bolts closest to the engine (see fig. 8.24).



25. Turn the timing belt adjuster bolt with an open-end wrench, move the pump forward toward the engine, then remove the belt from the pulleys.

26. Fit the new belt onto the pulleys, then turn the adjusting bolt to tighten the belt so that with moderate finger pressure it can be deflected approximately 12 mm at the midpoint between the two pulleys.



27. Tighten the fixing bolt, then the two mounting bolts.

28. Install the alternator belt as described in this paragraph.

29. Check the belt tension after a few minutes of engine operation, then, where provided, install the engine protection from below.

Air conditioning compressor drive belt

30. Remove the alternator drive belt and the power steering pump belt as described in this paragraph.

31. Loosen the compressor mounting bolt, unscrew the tensioner bolt to move the compressor forward toward the engine and remove the belt from the pulleys (see fig. 8.31).



32. Fit the new belt onto the pulleys, then tighten the adjusting bolt, tensioning the belt so that with moderate thumb force it can be deflected approximately 10 mm at the midpoint between the pulleys. When the tension is adjusted, tighten the mounting bolt.

33. Install the alternator and power steering pump belts as described in this paragraph.

34. Check the belt tension after a few minutes of engine operation, then, where provided, install the engine protection from below.

6-cylinder engines - replacing the drive belt

35. Remove the cooling fan blades and shroud as described in Chapter 3.

36. Loosen the tensioner bolt by a quarter to half a turn (if necessary, remove the plastic plug to gain access to the bolt) (see fig. 8.36).



37. Loosen the adjusting nut (counterclockwise) to move the adjuster back and remove the belt from the pulleys.

38. Route the new belt around the pulleys in the order shown, starting with the tensioner pulley (see Fig. 8.38, a. b). Make sure the belt is properly positioned on the pulleys.





39. Tighten the belt as follows.

Models with a graduated scale applied to the tensioner

40. Move the tensioner pointer until it is aligned with the right end of the scale (looking at the scale at the front of the engine compartment) (see fig. 8.40).



41. On vehicles without air conditioning, turn the adjusting nut clockwise until the tensioner pointer aligns with the 5th mark on the scale.

42. On models equipped with air conditioning, turn the adjusting nut clockwise until the tip of the pointer aligns with the 7th mark on the scale.

43. Tighten the tensioner bolt to the required torque and install the cover (where provided).

44. Install the radiator fan blades and shroud as described in Chapter 3.

Models with thick mark (and a cast triangle) not on the tensioner scale

45. Move the tensioner pointer so that it aligns with the right narrower end (looking at the scale at the front of the engine bay) triangle cabinets.

46. Turn the adjusting nut clockwise until the pointer tip aligns with the thick line (on the thicker edge of the triangle) on the scale (see fig. 8.46).



47. Tighten the tensioner bolt to the required torque and install the cover (where provided).

48. Install the radiator fan blades and shroud as described in Chapter 3.