Design and specification of the cooling system (Mercedes-Benz E-Class W123)

The liquid cooling system includes a radiator, expansion tank, centrifugal water pump and thermostat.

Water pump

The water pump is mounted on the right side of the cylinder block. On cars manufactured before 1985, the water pump is driven by a V-belt, which also drives the generator. On cars manufactured since 1985, it is driven by a multi-ribbed belt, which also drives other auxiliary engine units.

V-belt for generator drive

The belt tension is adjusted by moving the generator.

The belt tension is adjusted automatically by moving the tension roller. On M 102 engines, to ensure the initial belt tension, it is necessary to align the adjusting protrusion with the 7th mark (or from 5th for cars without power steering) on the tension roller.

Characteristic	Meaning
Belt tension when measured using the "Krikit" device, kgf
for a new belt	50
when reusing the belt	40—45
Belt type	Continental 9,5 1005La, Dayco 9,5 1000
Recommended Bosch belts (catalog number in brackets)
M 102	9,5x1005 (№ 1.987.947.625)
M 115	9,5x940 (№ 1.987.947.600)
M 123	9,5x940 (№ 1.987.947.600)
M 110	9,5x930 (№ 1.987.947.609)

Fan

Engine M 102

The fan is driven by the water pump shaft and switched on and off by an electromagnetic clutch controlled by a temperature sensor or a thermodynamic clutch.

Electromagnetic clutch

Characteristic	Meaning
Temperature,°C
inclusions	98—102
shutdowns	93—98
Distance between radiator and fan, mm	36
Radial clearance between fan and guide casing, mm
in the vertical plane	25
in the horizontal plane	20
Fan diameter, mm	380

Expansion tank

Characteristic	Meaning
Pressure in the cooling system, kg/cm², no more than	1,0—1,2
Opening pressure of the plug valve, kg/cm²
at intake	0,1
upon release
m 102 engines
valve marked "100"	1,0 ^+0,15 _–0,1 / 1,0 ⁺⁰ _–0,2 *
valve marked "120"	1,2 ⁺⁰ _–0,1 / 1,0 ⁺⁰ _–0,2 *

Material based on data from the portal MERCEDESMAN

* The numerator indicates the value for a new valve, the denominator indicates the value for a reused valve.

Thermostat

Characteristic	Meaning
Temperature of the beginning of opening of the main valve,°C	87
Temperature of full opening of the main valve,°C	102
Main valve stroke at 102°C, not less than, mm	8

Radiator

The radiator is aluminum, with horizontal tubes.

Characteristic	Meaning
Brand	Bechr.

Coolant

Characteristic	Meaning
Cooling system capacity, l	8,8
Coolant used	a mixture of distilled water and antifreeze recommended by Mercedes Benz (at temperatures down to -30°C)
Replacement frequency	every three years of operation