300SD (126.120) L5-3.0L DSL Turbo (617.951) (1982)
This condition remains in force as long as the engine maintains its normal operating temperature.
If the coolant temperature increases as the result of the higher load or higher outside temperatures, the air which flows through the radiator and actuates
the bimetallic strip will become warmer. The bimetallic strip (69) changes its shape under the increasing heat and opens at approx. 73 °C a valve by
means of a control pin (68) and thereby the path of the oil from reservoir (74) into working chamber (75), so that the fan will be additionally engaged.
During this control operation, the coolant temperature is between 90 and 95 °C.
With the clutch engaged, the fan Speed in lower speed range will increase approximately proportional with increasing engine speed, but will not exceed
3500/min in upper speed range.
Checking connecting temperature
Run engine at 4000 - 4500/min. As soon as a coolant temperature of 90 to 95 °C is attained1 the fan speed should increase by approx. 1000/min, which
can be clearly noticed acoustically.
Reconditioning
A defective coupling cannot be repaired with workshop equipment and a new coupling should therefore be installed.
Transportation and storage
Temperature-controlled viscofan couplings should be transported and stored vertically. For short periods - e.g. during assembly - the coupling may rest
on its flange, but never on front end.