Mercedes-Benz E-class W123 - Repair manual and operation

2.1.4. Krivoshipno-shatunny mechanism

Pistons

The piston from aluminum alloy with the flat bottom.

The tag of diameter of the piston and the shooter for orientation of the piston at its installation in the cylinder which has to be directed towards the camshaft drive are specified the bottom of the piston. On weight pistons of one engine should not differ from each other more than on 4,9 g.

Characteristic	Value
Gap between the piston and the cylinder, mm
nominal
M 102	0,016 — 0,040
for other models	0,025 — 0,035
maximum permissible in operation	0,10

Diameter of pistons *

Parameter, mm	Engine model
	M 115.938	M 102.920, M 102.939	M 102.980, M 102.982	M 115.954
nominal
class 1	86,98	88,968 — 88,982	95,468 — 95,482	93,73
class 2	—	88,978 — 88,992	95,478 — 95,492	—
class 3	—	88,988 — 89,002	95,488 — 95,502
1st repair size
class 1	87,48	89,468 — 89,482	95,968 — 95,982	94,13
class 2	—	89,478 — 89,492	95,978 — 95,992	—
class 3	—	89,488 — 89,502	96,988 — 96,002	—
2nd repair size
class 1	87,98	89,968 — 89,982	96,468 — 96,482	94,53
class 2	—	89,978 — 89,992	96,478 — 96,492	—
class 3	—	89,988 — 90,002	96,488 — 96,502	—
3rd repair size
class 1	88,48	—	—	—
Parameter, mm	M 123.920, M 123.921	M 110.923	M 110.984, M 110.988
nominal
class 1	85,98	85,98
class 2	—	—
class 3	—	—
1st repair size
class 1	86,48	86,48
class 2	—	—
class 3	—	—
2nd repair size
class 1	86,98	86,98
class 2	—	—
class 3	—	—
3rd repair size
class 1	—	—

* The difference of sizes is caused model year of release.

Piston fingers

Piston finger steel, polished, floating. From axial shift the finger is kept by lock rings.

Characteristics of piston fingers

Parameter, mm	Engine model
	M 102.920, M 102.939	M 102.980, M 102.982
Diameter
external	23,995 — 24,000
internal	15,5
Length	—
Gap between a finger and the plug of the top head of a rod	0,007 — 0,02
Gap between a finger and a lug of the piston	0,002 — 0,012

Piston rings

On the external surface of the piston three flutes for installation of rings are pierced. Situation at assembly: the tag of "Torahs" has to be directed up. On engines M 102 piston rings of Goyotze or TRW can be established.

Features of a design of piston rings of Goyotze

The top compression ring cylindrical, with a facet on an internal surface, with porous chromium plating of an external surface. The lower compression ring conical, with a fillet. An oil scraper ring with two facets, a razzhimny twisted spring and the chromeplated external surface.

Features of a design of piston rings of TRW

The top compression ring cylindrical, with a facet on an internal surface, with the chromeplated polished barrel-shaped external surface. The lower compression ring conical, with a fillet and the barrel-shaped chromeplated external surface. An oil scraper ring with two facets, with a razzhimny twisted spring and the chromeplated external surface.

Characteristic of piston rings

Parameter, mm	Engine model
	M 115.938	M 102.920, M 102.939	M 102.980, M 102.982	M 115.954
Gap on height
top compression ring	0,05 — 0,08	0,05 — 0,085	0,050 — 0,085
lower compression ring	0,03 — 0,06	0,01 — 0,03	0,03 — 0,06
oil scraper ring	0,01 — 0,04	0,01 — 0,045	0,01 — 0,04
Limit gap on height in operation
top compression ring	0,15
lower compression ring	0,10
oil scraper ring	0,16	0,10		0,16
Gap in the lock
top compression ring	0,30 — 0,55
lower compression ring	0,25 — 0,45
oil scraper ring	0,25 — 0,50
Limit gap in the lock in operation
top compression ring	1,0	1,0		1,0
lower compression ring	0,8	0,8		0,8
oil scraper ring	0,8	0,8		0,8
Parameter, mm	M 123.920, M 123.921	M 110.923	M 110.984, M 110.988
Gap on height
top compression ring	0,050 — 0,085
lower compression ring	0,03 — 0,06
oil scraper ring	0,01 — 0,04
Limit gap on height in operation
top compression ring	0,15
lower compression ring	0,10
oil scraper ring	0,16
Gap in the lock
top compression ring	0,30 — 0,55
lower compression ring	0,25 — 0,45
oil scraper ring	0,25 — 0,50
Limit gap in the lock in operation
top compression ring	1,0
lower compression ring	0,8
oil scraper ring	0,8

Rods

Double-T section rod steel, shod with replaceable inserts. Cover of the lower head of a rod of direct section. For an oil supply to the rubbing surfaces in a core of a rod the opening is drilled. On weight rods of one engine should not differ from each other more than on 5 g.

Characteristic	Value
Not parallelism and not planeness of openings of heads at measurement at distance of axes of 100 mm from a rod core, no more, than a mm
M 102	0,045
M 115	0,030
M 110	0,040
M 123	0,040
Roughness of a surface of connection of the piston with a rod, micron	0,002
Beating of openings of the lower head of a rod, no more, than a mm	0,02

Characteristics of rods

Parameter, mm	Engine model
	M 115.938	M 102.920, M 102.939	M 102.980, M 102.982	M 115.954
Diameter of the lower head of a rod	55,60 — 55,62	51,60 — 51,619		55,60 — 55,62
Diameter of the top head of a rod	29,00 — 29,02	27,00 — 27,021		29,00 — 29,02
Internal diameter of the plug of the top head	26,012 — 26,018	24,007 — 24,015		26,012 — 26,018
Distance between axes an opening of heads	148,95 — 149,05	144,95 — 145,05		148,95 — 149,05
Width of the lower head	32.08 — 32,10	27,857 — 27,90		32.08 — 32.10
Parameter, mm	M 123.920, M 123.921	M 110.923	M 110.984, M 110.988
Diameter of the lower head of a rod	51,60 — 51,62
Diameter of the top head of a rod	26,00 — 26,02
Internal diameter of the plug of the top head	23,007 — 23,013
Distance between axes an opening of heads	130,95 — 131,05
Width of the lower head	27,86 — 27,89

Rod cover bolts

Bolts with the extended core.

Characteristic	Value
Diameter of a carving	M9x1
Diameter of a core, mm
M 102
new bolts	8,3 — 8,4
maximum permissible	8,0
M 115
new bolts	8,3 — 8,4
maximum permissible	8,0
M 110
new bolts	7,3 — 7,4
maximum permissible	7,1
M 123
new bolts	7,3 — 7,4
maximum permissible	7,1
Bolt head height (M 102), mm	5,0 — 5,2
Length of a carving part (M 102), mm	40,0
Length to a head (M 102), mm	51,7 — 52,0

Bent shaft

Bent shaft steel, shod four - (engine M 123), five -  (engines M 102, M 115) or seven-basic (engine M 110).

The bent shaft of 4-cylinder engines (M 102, M 115) has eight counterbalances, 6-cylinder (M 110, M 123) — 12 counterbalances.

Characteristic	Value
Admissible face beating of cheeks of the radical bearing, mm	0,02
Radiuses of galitel of radical and conrod necks, mm	2,5 — 3,0
Diameter of the forward end of a bent shaft, mm	29,987 — 30,000
Admissible beating of the forward end of a bent shaft, mm	0,030
Diameter of a basic surface of a back epiploon, mm	92,874 — 92,928
Non-cylindricity of a flange, to, mm	0,02
Flange beating, to, mm	0,012
Beating of radical necks (the bent shaft is established on prisms of necks 1 and 5), to, mm
necks 2 and 4	0,07
necks 3	0.10

Gaps of a bent shaft of the engine M 102

Characteristic	Value
Diametrical gap between a radical neck and inserts, mm
nominal	0,025 — 0,045
extreme wear in operation	0,070
Diametrical gap between a conrod neck and inserts, mm
nominal	0,030 — 0,050
extreme wear in operation	0,070
Axial gap of a bent shaft, mm
nominal	0,06 — 0,22
extreme wear in operation	0,30
Axial gap between a rod and a bent shaft, mm
nominal	0,11 — 0,23
extreme wear in operation	0,50
Admissible ovality of radical and conrod necks in operation, mm	0,025
Admissible conicity in operation, mm
conrod necks	0,010
radical necks	0,015
Admissible imbalance of a bent shaft in operation, cm	15

Parameters of bent shafts

Parameter, mm	Engine model
	M 115.938	M 102.920, M 102.939	M 102.980, M 102.982	M 115.954
Diameter of radical necks
nominal
1 class	69,95 — 69,96	57,935 — 57,940		69,95 — 69,96
2 class	*	57,940 — 57,945		*
3 class	*	57,945 — 57,950		*
4 class	*	57,950 — 57,955		*
5 class	*	57,955 — 57,960		*
6 class	*	57,960 — 57,965		*
1st repair size	69,70 — 69,71	57,705 — 57,715		69,70 — 69,71
2nd repair size	69,45 — 69,46	57,455 — 57,465		69,45 — 69,46
3rd repair size	69,20 — 69,21	57,205 — 57,215		69,20 — 69,21
4th repair size	68,95 — 68,96	57,955 — 57,965		68,95 — 68,96
Width of radical necks
nominal	34,00 — 34,03	28,500 — 28,521 or 28,600 — 28,621		34,00 — 34,03
1st repair size	34,00 — 34,03	28,700 — 28,721		34,00 — 34,03
2nd repair size	to 34,60	28,900 — 28,921		to 34,60
3rd repair size	to 34,60	29,000 — 29,021		to 34,60
4th repair size	to 34,60	*		to 34,60
Distance between basic surfaces of persistent half rings
	—	23,979 — 24,000		—
Diameter of conrod necks
nominal	51,97 — 51,96	47,955 — 47,965		51,97 — 51,96
1st repair size	51,70 — 51,71	47,705 — 47,715		51,70 — 51,71
2nd repair size	51,45 — 51,46	47,455 — 47,465		51,45 — 51,46
3rd repair size	51,20 — 51,21	47,205 — 47,215		51,20 — 51,21
4th repair size	50,95 — 50,96	46,955 — 46,965		50,95 — 50,96
Width of conrod necks
nominal	32,0 — 32,1	27,000 — 28,034		32,0 — 32,1
repair size	to 32,30	to 28,30		to 32,30
Parameter, mm	M 123.920, M 123.921	M 110.923	M 110.984, M 110.988
Diameter of radical necks
nominal
1 class	59,95 — 59,96
2 class	*
3 class	*
4 class	*
5 class	*
6 class	*
1st repair size	59,70 — 59,71
2nd repair size	59,45 — 59,46
3rd repair size	59,20 — 59,21
4th repair size	58,95 — 58,96
Width of radical necks
nominal	29,00 — 29,02
1st repair size	29,00 — 29,02
2nd repair size	to 29,60
3rd repair size	to 29,60
4th repair size	to 29,60
Distance between basic surfaces of persistent half rings
	—	—	—
Diameter of conrod necks
nominal	47,95 — 47,96
1st repair size	47,70 — 47,71
2nd repair size	47,45 — 47,46
3rd repair size	47,20 — 47,21
4th repair size	46,95 — 46,96
Width of conrod necks
nominal	28,00 — 28,08
repair size	to 28,30

Inserts of radical and conrod bearings

Color of marking of inserts of bearings: blue or gray.

Characteristic	Value
Width of inserts, mm
Engines M 102 and M 115
nominal	33,80 — 33,90
repair	34,40 — 34,60
Engines M 110 and M 123
nominal	28,78 — 28,90
repair	29,40 — 29,60

Inserts for all steps of repair are delivered with excess on width and have to be finished by the size of the repolished bearing.

Engines of models M 102 releases since July, 1986 have thickness of inserts of radical bearings increased by 0,003 mm for reduction of a gap and noise reduction during the operation of the engine.

Characteristics of inserts of radical and conrod bearings

Parameter, mm	Engine model
	M 115.938	M 102.920, M 102.939	M 102.980, M 102.982	M 115.954
Thickness of an insert of the radical bearing
nominal	2,25	2,25		2,25
1st repair size	2,37	2,37		2,37
2nd repair size	2,50	2,50		2,50
3rd repair size	2,62	2,62		2,62
4th repair size	2,75	2,75		2,75
Thickness of an insert of the conrod bearing
nominal	1,80			1,80
1st repair size	1,92			1,92
2nd repair size	2,05			2,05
3rd repair size	2,17	2,18		2,17
4th repair size	2,30			2,30
Parameter, mm	M 123.920, M 123.921	M 110.923	M 110.984, M 110.988
Thickness of an insert of the radical bearing
nominal	3,50
1st repair size	3,63
2nd repair size	3,75
3rd repair size	3,88
4th repair size	4,00
Thickness of an insert of the conrod bearing
nominal	1,81
1st repair size	1,93
2nd repair size	2,06
3rd repair size	2,18
4th repair size	2,31

Flywheel of the engine M 102

The flywheel fastens eight bolts. The adjusting opening is opposite to drilling in a bent shaft.

Characteristic	Value
Diameter of the aligning fillet of a wreath, mm	275,31 — 275,39
Distance between a working surface of the conducted disk and a basic surface of a casing of coupling, mm	22,5 — 22,6
Distance between a working surface of the conducted disk and a head of a bolt of fastening of a flywheel, mm
nominal	16,6
after grinding, not less	15,5
Not planeness of a working surface of the conducted clutch plate, no more, than a mm	0,05
Outer diameter of a working surface of the conducted clutch plate, mm	222,0
Outer diameter of a basic surface of a casing of coupling, mm	253,0
Diameter of a core of compensation bolts of fastening of a flywheel, mm
for new bolts	8,5
minimum	8,0
Bolt length to a head, mm
for new bolts	22±0,2
maximum	22,5