Cooling system - Service Procedures
Speed check, fan disengaged 1 Run the engine at idling speed for 5 minutes. Air temperature in front of the fan must not exceed +30°C (+86°F).
Checking revs of thermostatically controlled cooling fan Warning! Keep your hand and the measuring instrument at a safe distance from the blades of the fan when checking revs.
The silicone fluid which, when the engine is switched off, ran into the drive chamber, is now pumped back to the storage chamber.
Faulty cut-in temperature 2 Increase engine speed to max rpm. Fan speed should now be 6.1–13.7 r/s (370–820 r/min). If the fan speed is not as specified above, the fan should be changed. Note! The fan must not be topped up with silicone fluid if the speed is too low.
If, despite the fact that the fan cut-in speed is correct, high coolant temperatures are suspected when driving, and also the fact that the fan cannot be heard engaging as coolant temperature rises, the fan cut-in temperature is probably incorrect. Fan cut-in temperature cannot be adjusted or checked in the vehicle since special instruments are required. If the cut-in/cut-out temperatures are suspected as being incorrect, the fan must be changed.
Checking revs of engaged cooling fan 1 The engine operating temperature should be high enough for the fan to be fully engaged.
Thermostatically controlled cooling fan, changing
2
A thermostatically controlled fan contains an accurately adapted amount of silicone fluid in order to function reliably.
Increase engine speed to max rpm. Fan speed should exceed 29 r/s (1740 r/min). If fan speed is lower, the fan should be changed.
For this reason, such a fan must always be stood vertically when out of the vehicle. If positioned horizontally, the silicone fluid may leak out, resulting in the fan losing its properties.
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