Crankshaft assembly,  OM617

Checking and correcting adjustment of TDC transmitter



03—345 Checking and correcting adjustment of TDC transmitter


Valve clearance
With engine
20 °C)
With engine warm
°C ±
15 °C)

















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


Tightening torque


Nuts for cylinder head cover


Special tools
om617 - 0122-1.jpg
001 589 65 09 00
Socket 27 mm, 1/2″ square for rotating engine
Measuring extension
123 589 09 63 00
Locating device for adjusting slide
116 589 19 21 00
Assembly mandrel for valve stem seals
617 589 00 43 00
Valve adjusting wrench 14 mm (2 each)
615 589 00 01 00
Holding wrench for valve spring retainer
615 589 00 03 00
Dial gauge holder
121 589 00 21 00
Magnetic dial gauge holder
116 589 12 21 00


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Conventional tool


Dial gauge A 1 DIN 878
e.g. made by Mahr, D-7300 Esslingen order no. 810


om617 - 0123-1.jpg
The pin in vibration damper should be accurately under TDC transmitter at crankshaft position 20° after TDC.
Check adjustment of TDC transmitter and make corrections, if required.
a)  When renewing TDC transmitter adjusting slide.
b)  When renewing crankshaft with balancing disc and vibration damper.
c)   When completing basic engines.
With the cylinder head removed, the measuring pin of the dial gauge can be set directly on piston crown. For this purpose, place magnetic dial gauge holder on cylinder crankcase parting surface.
For adjusting TDC transmitter, proceed in this case according to item 7, 14 and 17—24.
om617 - 0123-2.jpg




1    Remove fan cover. For this purpose, disconnect upper coolant hose on radiator.
2    Remove fan.
3    Remove V-belt of power-steering pump and refri­gerant compressor (13—340).
4    Remove double diaphragm or piston-vacuum pump.


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5 Disconnect regulating linkage to remove cylinder head cover. Pull out locking eye of longitudinal regulating shaft (arrow).
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.
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Model 116.120


Model 123
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On models 123 with automatic transmission 722.303 (W4A 040) and 126.120, pull off 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 - 0124-3.jpg
Model 126.120


6 Remove front rocker arm group.
For this purpose, set camshaft in such a manner that
the rocker arms are not under load.
Do not rotate engine on camshaft, but on crankshaft by means of tool combination.
om617 - 0124-4.jpg


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7 Set piston of 1st cylinder to TDC. Rotate crank­shaft with tool combination.
om617 - 0125-1.jpg




8 At intake valve of 1st cylinder, place holding wrench on hexagon of valve spring retainer.
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9    Unscrew cap nut (63) with valve adjusting wrench. For this purpose, apply counterhold to counternut (63a) by means of second valve adjusting wrench.
10    Unscrew counternut (63a).
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11    Remove valve spring retainer and valve spring.
12    Push off valve stem seal by means of a screw­driver or pull off by means of pliers.
Do not damage valve stem and valve guide.
13   Push valve on piston crown.
om617 - 0126-1.jpg


14    Reverse crankshaft for approx. 10 by means of tool combination.
15   Screw dial gauge holder with threaded sleeve to stud in cylinder head.
16    Insert dial gauge and screw measuring extension to dial gauge.
om617 - 0126-2.jpg


17    Place measuring arm on valve stem with 2 mm preload.
18   Slowly rotate crankshaft with tool combination in direction of rotation of engine until the large needle of the dial gauge stops (TDC position).
om617 - 0126-3.jpg


19   Unscrew TDC transmitter and pull out.
20    Loosen dial gauge and place measuring extension on valve stem at 5 mm preload. Rotate dial gauge scale until large needle points to zero.
21    Slowly rotate crankshaft with tool combination in direction of ratation of engine until dial gauge has moved back by 3.63 mm.
om617 - 0126-4.jpg


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22 Place locating device without handle (arrow) into adjusting slide.
Pin in balancing disc should enter groove of locating device.
If pin is not engaging, correct position of adjusting slide.
om617 - 0127-1.jpg


om617 - 0127-2.jpg
23    Loosen adjusting slide and displace until pin in balancing disc enters groove of locating device.
24   Screw down adjusting slide and remove locating device.


25    Insert TDC transmitter and tighten.
26    Remove dial gauge and unscrew dial gauge holder.
27    Lubricate new valve stem seal and mount with assembly mandrel. For this purpose, place an assembly sleeve on valve stem.
28    Install valve spring and rocker arm group.
om617 - 0127-3.jpg


29   Check valve clearance (05-210).
30   Mount cylinder head cover.
31    Install double diaphragm or piston-vacuum pump with new gasket.
32    Mount V-belt of powersteering pump and refri­gerant compressor and tension (13-340).
33   Attach fan and fan cover.


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