Removing and Installing Chain Tensioner

35 Cylinder heed
75 Closing plug
76 Sealing ring
77 Compression spring
78 Detent spring
79 Pressure bolt
83 Chain tensioner housing
84 Gasket
85 Tensioning rail

a Throttle bore 1.5 mm dia.
b Throttle bore 1.3 mm dia.

NOTE: This engine is provided with a hydraulic detent chain tensioner without valve.

During assembly and test jobs on chain drive, the chain tensioner need not be removed. In such cases it will be enough to remove the compression spring (77) (steps 3, 4, 11 and 12).

If, on the other hand, parts of the chain drive are renewed, remove chain tensioner and set pressure bolt into assembly position.






A Chain tensioner in assembly position
B Chain tensioner in operating position

When installing a new chain tensioner, also pay attention to assembly position (A). If the pressure bolt is too far forward (in last detent), the timing chain is extensively tensioned or the detent spring (78) is stuck in detent.






A 1st version
B 2nd version

On engine 617.950 starting with engine end No.006223, the chain tensioner gasket (B) has been installed for reasons of standardization with engines 615, 616 and 617.912. On engines 617.951/952 from start of series.

Removal
1 Drain coolant.






2 On engines with EGR (USA), remove pipe line between EGR valve and exhaust manifold (arrow). For this purpose, unscrew shielding plate (10).






3 On model 123 with level control, unscrew line holder on thermostat housing (arrow).






4 Remove thermostat housing.






5 Unscrew closing plug (75) of chain tensioner.

Attention! Closing plug is under pressure of compression spring (77).






6 Remove compression spring (77).
7 Unscrew chain tensioner housing and pull out.






8 Pull out pressure bolt (79) in forward direction.
9 Thoroughly clean all parts.


Installation






NOTE: Prior to installing chain tensioner, the chain drive must be completely mounted.

10 Rotate engine with tool combination in direction of rotation once, so that timing chain is under tension.






75 closing plug
76 Sealing ring
77 Compression spring
78 Detent spring
79 Pressure bolt
83 Chain tensioner housing

11 Insert chain tensioner housing (83) with new gasket (84) and tighten.






12 Place pressure bolt (79) on assembly detent.
13 Insert compression spring (77).
14 Position closing plug (75) with new sealing ring (76) and tighten to 90 Nm.
15 For further installation proceed vice versa to removal.