Viscous fan
Pic. 4.50. Viscous coupling in the context: 1 - clutch housing; 2 – housing cover; 3 - pressure washer; 4 - reserve cavity; 5 - working cavity; 6 - pin; 7 - bearing; 8 – bearing axis; 9 - gasket; 10 - bimetallic plates; 11 - valve
viscous coupling (pic. 4.50), filled with silicone oil, is located in the middle of the fan impeller and is controlled by bimetallic plates. The bimetallic plates have a steel pin, which, at an ambient temperature of about +85°C, opens the passage of oil into the working cavity. Viscous silicone oil creates a force circuit between the pulley and the fan, under the influence of which the latter begins to drive air.
When the engine is cold, the clutch is practically disconnected - the oil is in the reserve cavity, so there is no energy consumption for ventilation. Fan RPM stays below 1000 min-1. It changes along with the engine speed, but only at low speeds. When 4500 min-1 is reached, the safety valve is activated, which limits the fan speed to 3300 min-1.
Checking the viscous fan
1. With the engine off, check the fan for ease of movement.
2. Make sure that the fan does not have strong axial and radial play.
3. Make sure that there are no traces of oil on the viscous coupling. If there is oil, then it must be replaced.
4. With the engine warm and the hood closed, set the rpm to 3000 min-1.
Pic. 4.51. Viscous coupling: 1 - impeller; 2 - clutch housing; 3 - impeller mounting bolts; 4 - bimetallic plates
5. Coupling (pic. 4.51) should start working at a coolant temperature of +90...+95°С. Otherwise, replace the clutch.
Electric fan
The electric fan is installed only on 4-cylinder engines. The cooling system of the 4-cylinder engine immediately «loaded» when the engine is idling or, for example, when driving in mountainous terrain. If suddenly the coolant temperature control lamp starts to light up intermittently, this indicates a malfunction of the fan. In this case, you can continue driving to the place of repair, after allowing the engine to cool down. In this case, the engine should not experience heavy loads and idle as little as possible.
Attention! With the engine stopped, but still hot, do not keep your hands in the area of the fan impeller! The fan can start working even when the ignition is off.
Checking the health of the fan
1. Check the fuse.
2. Disconnect the plug from the connector next to the thermostat housing.
3. Wire the plug. If the fan works, then the thermal switch is faulty. If it does not work, the fan is faulty or the cable is broken.
4. To continue driving, bridge the plug and insulate it. Also, insulate the mating part to avoid short circuit and dirt ingress.
5. When stopping or parking for a long time, be sure to remove the jumper wire to prevent battery discharge.