Removal and Replacement
L 19 mm
L1 22.5 mm
NOTE: Remove cylinder head only from cooled-down engine. Remove together with exhaust manifold and boost air pipe.
On engine 617.950 (USA) starting 1980, threaded bore(G) and seat bore in cylinder head for quick-start pencil element glow plugs have been extended by 3 mm (L and L1).
This cylinder head has been installed on engines 617. 951/952 from start of series.
In the event of repairs, the head can also be installed on engines 617.950 made at an earlier date. On the other hand, the cylinder head with shorter thread and seat bores should not be installed on engines with quick-start system, since a part of the quick-start effect will be lost.
For these engines the cylinder head gaskets require no retightening. As a result, no retightening of cylinder head bolts is required during 1st inspection (1000 - 1500 km) and in the event of repair, after driving 1000 - 1500 km.
The cylinder head gaskets welded in-between sheeting may be removed from package only directly prior to assembly, since they are sensitive to light and ozone.
Removal
Drain plug on cylinder crankcase
1 Completely drain coolant.
Model 116.120
1 Temperature switch 100 °C
2 Vacuum line
3 Vent line
4 Intake line
2 Remove air cleaner with intake line (4). For this purpose, pull off engine vent line (3) and on model 116.120 with double diaphragm vacuum pump, pull vacuum line (2) and cable from temperature switch (1).
3 On engines with EGR (USA) cover return line from cyclonic oil separator to oil pan (arrow).
4 On model 123 with level control, unscrew line holder from thermostat housing (arrow).
5 Disconnect the three coolant hoses (arrows) on thermostat housing and heater supply hose on cylinder head. Remove upper coolant hose to radiator.
6 Unscrew bleed line between cylinder head and water pump housing.
7 On model 123 with level control, remove hydraulic oil pump with connected lines and put aside.
For this purpose, unscrew screws (arrows).
8 Loosen oil filter cover and pull up for a short distance.
9 Unscrew exhaust on exhaust gas turbo-charger (arrow) and on transmission.
10 Unscrew oil dipstick guide tube of automatic transmission on boost air pipe.
11 Completely unscrew oil feed line for exhaust gas turbo-charger.
12 Unscrew line (a) on boost air pipe.
13 Remove injection line and cover connections.
14 Unscrew or pull off cable harness on pencil element glow plugs, on pressure switch in boost air pipe and on (USA) up to 1980 on temperature switch.
15 Pull fuel return line from 1st injection nozzle.
16 On models 123 and 126.120 with cruise control tempomat, unscrew actuator with holder on power steering pump carrier, disconnect linkage and put actuator aside.
17 Remove power steering pump with bracket and fuel filter and put aside.
For this purpose, unscrew the five screws indicated by arrows.
Do not disconnect hoses and lines.
18 Remove exhaust turbo-charger.
For this purpose, unscrew holder (6) for air filter. Cover oil return pipe (arrow).
19 Unscrew exhaust manifold support on manifold (arrow).
Model 116.120
20 Remove cylinder head cover. For this purpose, disconnect regulating linkage. Pull out locking eye of longitudinal regulating shaft (arrow).
Model 123
On models 116.120 and 123, pull longitudinal regulating shaft out of rubber mount in forward direction and remove in rearward direction.
Model 126.120
On model 126.120, pull longitudinal regulating shaft out of guide lever in rearward direction and remove in forward direction.
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.
21 Loosen necked-down screw for attaching camshaft sprocket, do not screw out.
For loosening camshaft sprocket, apply counterhold with a screw driver or a steel bolt.
22 Remove both rocker arm groups. For this purpose, set camshaft in such a manner that the rocker arms are not under load.
23 Set engine to ignition TDC of 1st cylinder. For this purpose, rotate engine at crankshaft by means of tool combination.
24 Mark camshaft sprocket and timing chain in relation to each other.
25 On engines with EGR (USA) remove pipe line between EGR valve and exhaust manifold (arrow). For this purpose, unscrew shielding plate (10).
26 Unscrew closing screw of chain tensioner and remove compression spring.
27 Remove slide rail in cylinder head. Pull out bearing bolt by means of impact puller.
28 Remove camshaft sprocket.
Tightening Diagram:
29 Loosen cylinder head bolts in reverse order of tightening diagram by means of Allen wrench insert and screw out.
Unscrew the M 8-screws by means of Allen wrench 6 mm, 440 mm long.
30 Remove injection nozzles to remove the 5 screws adjacent to injection nozzles.
Suspension eye front
Suspension eyes rear
31 Lift Out cylinder head. This can also be done by means of a crane and an engine hoist (Motordirigent). Suspend the cables for this purpose at the three suspension eyes.
32 Pull out thrust bolts of installed chain tensioner in inward direction (arrow).
33 Thoroughly clean cylinder crankcase and cylinder parting surface.
Installation
34 Mount new cylinder head gasket.
35 Mount cylinder head while paying attention to hollow dowel pins for locating cylinder head.
36 With double hex. cylinder head bolts, measure length (L) of screws. If the dimension shown in table is exceeded, use new cylinder head bolts. Cylinder Head Bolts and Cylinder Head Bolt Torquing
Tightening Diagram:
37 Lubricate cylinder head bolts on threads and on head contact surface and insert.
38 Tighten cylinder head bolts in steps in sequence of tightening diagram, starting with bolt 1.
Attention! Tighten hex. socket cylinder head bolts to torque and fix double hex. socket cylinder head bolts to initial torque preload and angle of rotation. Cylinder Head Bolts and Cylinder Head Bolt Torquing
Estimate angle of rotation. For this purpose, place adjustable torque wrench in release position (locked) into plug-in ratchet. Position adjustable torque wrench with plug-in ratchet in longitudinal relation to engine and turn until wrench is transverse to engine.
When tightening to angle of rotation torque, do not use bending bar-torque wrench.
When tightening to angle of rotation torque, do not use bending bar-torque wrench.
Hex. socket cylinder head bolts (A)
Step1 170 Nm
Step2 90 Nm
Setting interval 10 min
Step3 100 Nm
Double hex. socket cylinder head bolts (B)
Step 1 40 Nm
Step 2 70 Nm
Setting interval 10 min
Step 3 90°
Step 4 90°
Tighten M 8 bolts by means of Allen wrench with tommy handle.
39 Place camshaft sprocket with timing chain on camshaft. Pay attention to color marks.
40 Position necked-down screw for attaching camshaft sprocket and tighten to 80 Nm (8 kpm).
For this purpose, apply counterhold to camshaft sprocket by means of a screw driver or a steel bolt.
41 Install both rocker arm groups.
42 Rotate engine at crankshaft by means of tool combination and set to ignition TDC of 1st cylinder. Check adjusting marks.
If the cylinder head has been faced, check timing.
43 Install slide rail.
44 Insert thrust bolts and compression spring of chain tensioner from outside.
Position closing plug with new sealing ring and tighten to 90 Nm.
45 Adjust valve clearance. Valve Clearance
46 Install injection nozzles. Insert new nozzle reeds first.
47 Screw-on exhaust manifold support.
48 Install exhaust gas turbo-charger with new gasket. When positioning turbo-charger, pay attention to oil return pipe. Remove cover.
49 Unscrew oil feed line for exhaust gas turbo-charger. Insert new gasket for exhaust gas turbo-charger.
50 For further installation proceed vice versa to removal.
51 Add coolant (20-010) and pressure-test cooling system.
52 Bleed injection system by means of a hand pump.
53 Run engine and check for leaks.
NOTE: Retightening of cylinder head bolts and setup of valve clearance on warm engine not required.