Reset chain tensioner - AR05.10-P-7800-03MM

ENGINE 152, 157, 276, 278 

Fig 1: Setting Chain Tensioner

Courtesy of MERCEDES-BENZ USA

Chain tensioner in an extended condition 

Chain tensioner in the block position clamped in the vise 

Chain tensioner in the block position with drift 

The chain tensioner (1) may only now be reset and reused if it did not have any noticeable problems during previous use and all components of the chain drive do not show any signs of damage or no components of the chain drive were replaced.

The chain tensioner (1) is pretensioned by an internal spring and moves out autonomously when being removed. If the chain tensioner (1) does not moves out completely autonomously  then the chain tensioner (1) is not suitable for reuse and must be replaced by a new chain tensioner (1).

1. Measure chain tensioner (1) using a vernier caliper The chain tensioner (1) must be extended completely after removal and must reach the extended dimension (a) shown (see Fig 1). Only a completely extended chain tensioner (1) can be reset. If the chain tensioner (1) does not extend autonomously  then it must be replaced by a new chain tensioner (1).
2. Insert, reset and secure chain tensioner (1) in the vise (4) Secure: Use a suitable drift (5) with a diameter of 3 mm to secure the chain tensioner (1).

   Reset: A vise (4) with plastic protective jaws is needed (see Fig 1) to reset the chain tensioner (1). Ensure when inserting the chain tensioner (1) in the vise (4) that the transport hooks (1c), the interference contour (1b), the chain tensioner housing and the plastic cap (1e) on the tensioning cylinder (1d) are not damaged.

   The chain tensioner (1) must be reset back to the block position through turning together of the clamping jaws on the vise (4). Oil leaks out of the high pressure chamber through the leak gap and through the pressure relief valve. The block position is recognizable due to the significant increase in force. In the block position just the groove between the plastic cap (1e) and tensioning cylinder (1d) is visible, in which the drift (5) must be inserted.

   If the block position is reached then the chain tensioner (1) is fixed in this position using a drift (5). The tensioning cylinder (1d) for chain tensioner (1) must pretension the drift (5) (see Fig 1) when releasing the clamping jaws.

   if the drift (5) is removed the chain tensioner (1) should again extend completely on its own. The procedure described above can be repeated. If the block position is not reached then the chain tensioner (1) is arrested in an intermediate position and does not extend completely on its own or does not operate correctly in the engine and must be replaced by a new chain tensioner (1).