A new belt tensioning system for some VAG 1.8/2.0 petrol engines


At OES level, there has been a modification of the tensioning system on some (not all!) VAG 1.8/2.0 petrol engines which use the equivalent of the Gates 5491XS belt in the aftermarket. Let’s take a closer look at this modification and its possible consequences. 

Out with the hydraulic, in with the mechanical 

The modification in question comes down to a shift from a hydraulic tensioning system to a mechanical tensioning system which means – for some applications – that the initial Gates K03/KP3 and K04/KP45491XS kits will be replaced by the new Gates K085491XS kit and the related kits including a water pump: KP85491XS-1 and KP85491XS-2.

To be more precise: what happened is that the hydraulic tensioning system, which consisted of tensioner T43018 and vibration damper T43028, has been replaced by a new mechanical tensioning system featuring a new tensioner T43242 and a new idler bracket T42313.

(Left) Hydraulic tensioning system - (Right) Mechanical tensioning system

The new idler bracket (T42313) looks almost exactly the same as the old vibration damper (T43028), but without the hydraulic element: it’s only a metal bracket with a small touch idler. The reason is that the function which the hydraulic element used to fulfil has now been integrated into the new tensioner itself.

New belt tensioning system: the consequences 

1. Components of two tensioning systems are not interchangeable

The separate components of the old, hydraulic tensioning system are not compatible with the components of the new, mechanical tensioning system:
  • The new tensioner (T43242) cannot be used in combination with the old hydraulic element (T43028).
  • The new bracket (T42313) cannot be used in combination with the old tensioner (T43018).
N.B.: failure to comply with these instructions will result in serious engine damage

2. The modification does not affect all applications

Second, it is important to note that the modification affects only some VAG 1.8/2.0 petrol engines. This means that the K03/KP3 and K04/KP4 kits will remain valid for some applications, as still prescribed by OE. We strongly recommend that you check the Gatesautocat online catalogue to determine which tensioning system or kit you should use, and to always follow the tensioning procedure given in the installation instruction.