Cooling System
11---1
11. COOLING SYSTEM
A. Thermostat
211--- 1
The thermostat is of a two---way type. Its opening temperature
is 79
˚
C. In winter a thermostat can be used with an opening
temperature of 83
˚
C.
Check the function of the thermostat as follows:
--- Lower the thermostat into a vessel of boiling water so that
the thermostat does not touch the sides or bottom.
--- Opening must begin under 20 seconds.
--- The thermostat must be fully open under 50 seconds.
Stroke, see specifications point
thermostat
.
211--- 2
Some 620/634---engines have two separate thermostats.
These are separated from the type of the single thermostat
and they are not interchangeable. To these engine there are
no separate winter thermostats.
Note!
Modification of the by---pass pipe.
320/420---engines from engine number D 3056
620---engines from engine number D 3532
211--- 3
The rubber seal ring between the coolant pump and the ther-
mostat housing has been modified to two o---ring seals.
At the same time also the by---pass pipe is modified. The new
parts can, during a repair, be installed instead of the earlier
used.
B. Reconditioning coolant pump
(320, 420)
1. Drain the engine coolant. Disconnect the water hoses from
the thermostat housing and from the coolant pump. Remove
the thermostat housing and the by---pass pipe.
2. Slacken the alternator fixing bolts. Remove the fan and the
pump belt pulley. Remove the v---belt.
3. Detach the coolant pump. Remove the pump rear plate and
clean the sealing surfaces.
9052 48900
211--- 4
4. Remove the fan hub using puller 9052 48900. Remove the
circlip from the pump body.
