Dodge Nitro. Manual - part 522

2. Install shroud mounting bolts tighten bolts to 10 N.m (89 in. lbs.).  

3. Connect fan motor wire connector to harness connector, and attach connector to shroud.  

4. Connect battery negative cable.  

5. Start engine and check fan operation.  

FAN-VISCOUS RADIATOR 

DESCRIPTION 

DESCRIPTION 

Fig. 55: Identifying Viscous Fan Drive, Thermostatic Spring, Mounting Nut To Water Pump Hub 
Courtesy of CHRYSLER LLC 

1 - VISCOUS FAN DRIVE
2 - THERMOSTATIC SPRING
3 - MOUNTING NUT TO WATER PUMP HUB

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

The thermal viscous fan drive (1) is a silicone-fluid-filled coupling used to connect the fan blades to the water 
pump shaft. The coupling allows the fan to be driven in a normal manner. This is done at low engine speeds 
while limiting the top speed of the fan to a predetermined maximum level at higher engine speeds. See Fig. 55. 

OPERATION 

OPERATION 

A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit. This spring coil 
reacts to the temperature of the radiator discharge air. It engages the viscous fan drive for higher fan speed if the 
air temperature from the radiator rises above a certain point. Until additional engine cooling is necessary, the 
fan will remain at a reduced RPM regardless of engine speed. Normally less than 800 RPM.  

Only when sufficient heat is present, will the viscous fan drive engage. This is when the air flowing through the 
radiator core causes a reaction to the bimetallic coil. It then increases fan speed to provide the necessary 
additional engine cooling. 

Once the engine has cooled, the radiator discharge temperature will drop. The bimetallic coil again reacts and 
the fan speed is reduced to the previous disengaged speed. 

DIAGNOSIS AND TESTING 

VISCOUS RADIATOR FAN 

If the fan assembly free-wheels without drag (the fan blades will revolve more than five turns when spun by 
hand), replace the fan drive. This spin test must be performed when the engine is cool. 

For the following test, the cooling system must be in good condition. It also will ensure against excessively high 
coolant temperature. 

1. Drill a 3.18-mm (1/8-in) diameter hole in the top center of the fan shroud.  

2. Obtain a dial thermometer with an 8 inch stem (or equivalent). It should have a range of -18° to 105°C (0° 

to 220°F). Insert thermometer through the hole in the shroud. Be sure that there is adequate clearance 
from the fan blades.  

3. Connect a tachometer and an engine ignition timing light (timing light is to be used as a strobe light).  

4. Block the air flow through the radiator. Secure a sheet of plastic in front of the radiator (or air conditioner 

CAUTION: If the viscous fan drive is replaced because of mechanical damage, the 

cooling fan blades should also be inspected. Inspect for fatigue cracks, 
loose blades, or loose rivets that could have resulted from excessive 
vibration. Replace fan blade assembly if any of these conditions are found. 
Also inspect water pump bearing and shaft assembly for any related 
damage due to a viscous fan drive malfunction.

WARNING:

Be sure that there is adequate fan blade clearance before drilling.

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

condenser). Use tape at the top to secure the plastic and be sure that the air flow is blocked. 

5. Be sure that the air conditioner (if equipped) is turned off. 

6. Start the engine and operate at 2400 RPM. Within ten minutes the air temperature (indicated on the dial 

thermometer) should be up to 93°C (200°F). Fan drive engagement should have started to occur at 
between 91° to 96°C (195° to 205°F). Engagement is distinguishable by a definite increase in fan flow 
noise (roaring). The timing light also will indicate an increase in the speed of the fan.  

7. When the air temperature reaches 93°C (200°F), remove the plastic sheet. Fan drive disengagement 

should have started to occur at between 62° to 85°C (145° to 185°F). A definite decrease of fan flow 
noise (roaring) should be noticed. If not, replace the defective viscous fan drive unit.  

REMOVAL 

REMOVAL-3.7L/4.0L 

1. Partially drain the cooling system. See STANDARD PROCEDURE.  

2. Remove the upper radiator hose.  

3. Remove the air filter housing assembly. Refer to REMOVAL . 

Fig. 56: Using Tool 6958 And Adapter Pins 8346 To Remove Fan/Viscous Fan Drive Assembly 
From Water Pump 
Courtesy of CHRYSLER LLC 

4. Using Tool 6958 and adapter pins 8346 (1), remove fan/viscous fan drive assembly from water pump. Do 

not attempt to remove fan/viscous fan drive assembly from vehicle at this time.  

WARNING:

Use extreme caution when the engine is operating. Do not stand in a 
direct line with the fan. Do not put your hands near the pulleys, belts 
or fan. Do not wear loose clothing.

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

5. Position the fan/fan drive assembly in the radiator shroud.  

6. Remove the two shroud mounting screws.  

7. Remove the radiator shroud and fan drive assembly.  

8. After removing fan blade/viscous fan drive assembly, do not place viscous fan drive in horizontal 

position. If stored horizontally, silicone fluid in the viscous fan drive could drain into its bearing assembly 
and contaminate lubricant.  

9. Remove four bolts securing fan blade assembly to viscous fan drive.  

REMOVAL-2.8L DIESEL 

Fig. 57: Identifying Special Tool 6958 Spanner Wrench & Fan 
Courtesy of CHRYSLER LLC 

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro