Engine timing, valves,  OM617

Removal and installation of valve springs



05—250 Removal and installation of valve springs


Valve clearance
with engine cold (approx. 20
with engine warm (60 °C ± 15






M 0.05 mm higher during lasting outside temperatures below —20 °C.


Tightening torques
Nuts for cylinder head cover
Rocker arm bearing brackets to cylinder head
Special tools



Valve adjusting wrench 14 mm (2 each)
om617 - 0173-1.jpg
615 589 00 01 00
Holding wrench for valve spring retainer
615 589 00 03 00
Socket 27 mm, 1/2″ square, for rotating engine
001 589 65 09 00
Contact handle for rotating engine (component of compression pressure recorder 001 589 46 21 00)
001 589 46 21 08


om617 - 0173-2.jpg
Each valve has one valve spring (64) and one rotocap (69).
On engines with long service life, it is recommended to renew rotocaps at the same time.
23 Valve guide                    66 Valve stem seal
62    Valve spring retainer 69 Rotocap
63    Cap nut                          70 Valve 63a Counternut
64    Valve spring


05.8-250/1 F 2




Valve springs with higher spring tension are installed on engine 617.950 since January 1979 and on engines 617.951/952 since start of series (05-260).
On engine 617.950 (usa) starting model year 1980 with increased output and on engines 617.951/952, do not install valve spring, part No. 180 053 06 20.
On the other hand, on engine 617.950 (usa) up to model year 1980 with increased output, valve spring part No. 615 053 01 20 may also be installed.


Start of series


Starting chassis No.


617.950 617.951/952
006303 start of series


Valve spring, part No. 180 053 06 20, two green or purple-green color dots.
Valve spring, part No. 615 053 01 20, two yellow or purple-yellow color dots.
Renew damaged cap nuts (63).
Cap nuts are available in three versions:


1st version


Cap nut with small supporting surface (A).


2nd version
Cap nut reinforced in upper range, with larger sup­porting surface (B).


3rd version


Cap nut reinforced in upper range and hard-chromed.
om617 - 0174-1.jpg
Identification: silver colored.


05.8-250/2 F 2




On engines with chilled cast iron camshaft and rocker arms with carbide facing, only the hard-chromed cap nut may be installed.
The hard-chromed cap nut can also be installed on engines with chilled cast iron camshafts and rocker arms with inductance-hardened and hard-chromed running surface.
Spare parts (ET) Sindelfingen will keep only hard-chromed cap nuts in stock.


om617 - 0175-1.jpg
1 Disconnect regulating linkage to remove cylinder head cover. Pull out locking eye of longitudinal regu­lating shaft (arrow).
Model 116.120


On models 116.120 and 123, pull longitudinal regu­lating shaft out of rubber mount in forward direc­tion and remove in rearward direction.
On model 126.120 pull longitudinal regulating shaft out of guide lever in rearward direction and remove in forward direction.
om617 - 0175-2.jpg
Model 123


On models 123 with automatic transmission 722.303 (W 4 A 040) and 126.120, disconnect central plug for vacuum lines (71) or vacuum lines. Disconnect Bowden wire, compress black plastic clip (arrow) and pull Bowden wire out of holder in rearward direction.
om617 - 0175-3.jpg
Model 126.120


05.8-250/3 F 2




2 Remove rocker arm with rocker arm bearing brackets (05-235).
om617 - 0176-1.jpg


3 Set piston of respective cylinder to ignition TDC.
For this purpose, rotate crankshaft with tool com­bination.
om617 - 0176-2.jpg




4 Place holding wrench on valve spring retainer.
om617 - 0176-3.jpg


5   Unscrew cap nut (63) by means of valve adjusting wrench.
For this purpose, apply counterhold to counternut (63a) by means of second valve adjusting wrench.
6   Unscrew counternut (63a).
7    Remove valve spring retainer and valve spring.
8   Check valve spring, renew according to condition (05-260).
om617 - 0176-4.jpg


05.8-250/4 F 2




om617 - 0177-1.jpg
9 Insert valve spring with narrow coils toward cylinder head (color dots at top).




10   Mount valve spring retainer.
Lug on valve spring retainer (arrow) should be seated in groove on valve stem.
11    Screw on counternut and cap nut.
12    Install rocker arm with rocker arm bearing brackets (05-235).
13   Adjust valve clearance (05—210).
14   Mount cylinder head cover.
om617 - 0177-2.jpg


Valve timing


om617 - 0177-3.jpg


57    Tensioning spring
58    Rocker arm shaft 58a Rocker arm shaft
59    Rocker arm
59a Rocker arm bearing bushing
62    Valve spring retainer
63    Cap nut 63a Counternut
64    Valve spring
65    Bearing bracket
66    Valve shaft seals
67   Screw 67a  Washer
68    Fitted sleeve
69    Rotocap
70    Intake valve
71    Exhaust valve


05.8-250/5 F 2