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Timing belt replacement

Here you will find useful basic information and handy tips for replacing the toothed belt in vehicles.

Primarily, the toothed belt drives the camshaft(s) and ensures the correct valve timing. In many cases, it also drives ancillary units, such as the coolant pump. The toothed belt is a wearing part and must be replaced at regular intervals. On this page we will show you the causes that may lead to premature failure of the toothed belt, and provide practical tips for professional toothed belt replacement.

Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle garages in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.

 

TIMING BELT KIT: BASIC PRINCIPLES

During replacement of the toothed belt, all belt drive components should be replaced, too. For this, Behr Hella Service provides complete kits incl. coolant pump, toothed belt, as well as any tensioner pulleys, deflection rollers, guide pulleys, shock absorbers, and seals required. Through this, the time-consuming search for individual components is not necessary.

 

Completely replacing all components provides the best possible protection against subsequent repairs and warranty claims. All parts are perfectly coordinated with each other and meet the high Behr Hella Service quality demands.

Structure and function

The toothed belt, also called the timing belt, is a drive belt with toothing. It drives the toothed pulley of the crankshaft and camshaft in an interlocking way, and is responsible for adherence to the valve timing.

 

For many vehicles the coolant pump and other ancillary units are also driven via a toothed belt. Different tensioner pulleys and guide pulleys are responsible for the tensioning and guiding of the belt. The actual power transfer of the belt is realised by an embedded tensile belt which is generally composed of aramid or glass fibres. To protect the teeth, which are made of elastomer, against wear, the inside of the belt is made of a wear-resistant textile.

 

For special forms, teeth are affixed to both the inside as well as outside of the belt.

FAULTY TIMING BELT: CAUSE OF FAILURE

The belt must be replaced in intervals specified by the vehicle manufacturer. If the replacement intervals or installation instructions are not complied with, there is the risk of damage to components and the engine.

DAMAGED TEETH:

  • Toothed belt is too loose
  • Impact of foreign bodies
  • Tension too high
  • Tensioner pulley that is stuck

CRACKS ON THE BACK OF THE BELT

  • Toothed belt is tensioned too tightly
  • Guide pulley is stiff
  • Belt is too old

WEAR AT THE EDGES OF THE TOOTHED BELT

  • The belt is in contact with the pulley
  • Belt is not aligned
  • Faulty pulley

TOOTHED BELT FLUTTERS/MAKES CONTACT

  • Belt is too loose
  • Faulty tensioner pulley adjustment

CRACKED TOOTHED BELT

  • Tension too high
  • Foreign bodies in the belt drive
  • Toothed belt kinked during mounting
  • Excessive aging

BROKEN BASE PLATE

  • Faulty tensioner pulley basic setting

VARIOUS NOISES

  • Whistling noises due to belt tension being too high
  • Grinding noises due to bearing damage
  • Load reversal noises due to faulty torsional vibration dampers
  • Toothed belt makes contact with cover

REPLACING TIMING BELTS: WORKSHOP TIPS

When replacing the toothed belt kit, the specifications on the product instruction leaflet and the installation instructions of the vehicle manufacturer must be noted. The required special tools should also be used for correct assembly.

 

During replacement of the toothed belt, pay attention to the functional capability and the state of any alternator freewheel clutch (Figure 5, item A) and torsional vibration damper (Figure 6) installed. Furthermore, the components of the power take-off should also be checked (flat belt with tensioner pulleys and rollers, tensioning element). If, during the replacement of the coolant pump, it becomes evident that the cooling system is contaminated, it should be flushed. The HELLA cooling system cleaner is suitable for this, for example. The cooling system should only be filled with a coolant which meets the specifications of the vehicle manufacturer. The system should be filled and bled in accordance with the specifications of the vehicle manufacturer.

 

Information on the use, specifications and change intervals of coolant can be found in the corresponding technical information on coolant.

 

Information on the correct installation of coolant pumps can also be found in the applicable technical information.

 

Once the work is complete attach the service sticker, which documents the replacement of the belt, in a visible place in the engine compartment and also document the toothed belt replacement in the vehicle service book.

HOW TO REPLACE A TIMING BELT: VIDEO

Toothed belt replacement

Replacement of the toothed belt on the example of a VW Golf V with 1.6 litre petrol engine.

 

04:35 min