Sequence of works
1. Mark the direction of travel on the outside of the belt with a felt-tip pen. If you put the accessory drive belt on incorrectly, it will wear out quickly. When installing the belt, make sure that the belt grooves fit exactly into the pulley grooves.
Fig. 4.26. Auxiliary drive belt tensioner: 1 – tensioner lever with hole; 2 – lock nut; 3 – tension spring; 4 – pulley; 5 – pulley lever; 6 – vibration damper
2. On all engines except CDI: unscrew the lock nut 2 (Fig. 4.26) at the spring attachment point.
3. Insert the crowbar from above into the spring tension lever 1 and press it back enough to remove the fixing bolt.
4. Remove the lever.
5. Move pulley 4 back slightly and remove the accessory drive belt.
Fig. 4.27. Loosening the belt tension
6. On CDI engines: Place a Torx key (E10) on the pulley and turn it counterclockwise (Fig. 4.27) until the belt loosens. Remove the accessory drive belt.
7. Pass the belt between the impeller and the fan shroud and remove it. You can detach the fan shroud from the radiator and remove the belt.
8. Check the condition of the pulleys and clean them. Pay attention to the play of the guide and tension pulleys.
9. Check the belt for wear and clean it from dirt.
Auxiliary drive belt breakage
If the red battery charge indicator light comes on while driving, the belt may be broken. Often, when the belt breaks, you can hear a dull thud on the metal in the engine compartment.
You cannot continue driving, because the coolant pump will not work. Otherwise, the coolant will quickly boil, the engine will overheat and get seriously damaged. Do not risk driving even at low speed with stops. If you do not have a spare belt in your car, it is better to tow the car to the parking lot.
Fig. 4.28. Installing the accessory drive belt on the tensioner pulley: 1 – cooling system pulley; 2 – tensioner pulley (removed); 3 – crankshaft pulley
Fig. 4.29. Location of the auxiliary drive belt for engines 220 D, 290 TD, 300 D: 1 – coolant pump; 2 – tensioner pulley; 3 – servo drive hydraulic pump pulley; 4 – three-phase current generator; 5 – crankshaft pulley; 6 – air conditioning compressor
10. Thread the new accessory drive belt through the fan blades (fig. 4.28, 4.29).
11. Pass the belt through the pulleys, observing the order of its installation.
12. On all engines except CDI: tighten the belt. To do this, use the lever to pull the tensioner spring until you can put the tensioner bolt on the lever.
13. Tighten the nut.
14. On CDI engines: To install the belt, tighten the tensioner pulley with a Torx key.
15. Slowly loosen the pulley until the accessory drive belt can be put on.
Fig. 4.30. Mutual position of pulleys: 1 – body; 2 – pulley lever; 3 – pulley; 4 – Torx screw; A – area of location of marking "B"; B - marking
16. Check that the belt is correctly positioned in the pulley grooves (Fig. 4.30).