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Engine Cooling Fans - Except Dakota Dodge Cab & Chassis R2500

Cooling Fan 3 illustrations ~1277 words

DESCRIPTION & OPERATION

WARNINGVehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article in RESTRAINTS.
CAUTIONWhen battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

VISCOUS FAN DRIVE

CAUTIONSome engines equipped with serpentine drive belt have rotating fans and viscous fan drives. They are marked with the word REVERSE to designate their usage. Installation of the wrong fan or viscous fan drive can result in engine overheating.
CAUTIONIf 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 is any of these conditions are found. Also inspect water pump bearing and shaft assembly for any related damage due to viscous fan drive malfunction.

The thermal viscous fan drive is a silicone-fluid-filled coupling used to connect the fan blades to the water pump shaft. (Scheme 1)and (Scheme 2). 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.

A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit. (Scheme 3) 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.

Only when a 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.

Scheme 1

Scheme 1
Scheme 1

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

RADIATOR FAN

CAUTIONIf fan blade assembly is replaced because of mechanical damage, water pump and viscous fan drive should also be inspected. These components could have been damaged due to excessive vibration.

Note. For additional information, see VISCOUS FAN DRIVE .

Inspection

The fan cannot be repaired. If fan is damaged, it must be replaced. Inspect fan as follows

  1. Remove fan blade and viscous fan drive as an assembly from the engine. See «COOLING FAN (GASOLINE)»(/dodge/cab-chassis-r2500/1996-2002/remont/cooling-fan/#engine-cooling-fans-except-dakota__cooling-fan-gasoline) .
  2. Remove fan blade assembly fro viscous fan drive unit (four bolts).
  3. Lay fan on a flat surface with leading edge facing down. With tip of blade touching flat surface, replace fan if clearance between opposite blade and surface is greater than .090" (2.0 mm). Rocking motion of opposite blades should not exceed .090" (2.0 mm). Test all blades in this manner.
  4. Inspect fan assembly for cracks, bends, loose rivets or broken welds. Replace fan if any damage is found. WARNING: DO NOT attempt to bend or straighten fan blades if not within specifications.

Noise

It is normal for fan noise to be louder (roaring) when

  1. The underhood temperature is above the engine component point for the viscous drive coupling. This may occur when ambient (outside air temperature) is very high.
  2. Engine loads and temperatures are high such as when towing a trailer.
  3. Cool silicone fluid within the fan drive unit is being redistributed back to its normal disengaged (warm) position. This can occur during the first seconds to one minute after engine start-up on a cold engine.

Leaks

Viscous fan drive operation is not affected by small oil stains near the drive bearing. If leakage appears excessive, replace the fan drive unit.

CAUTIONSome engines equipped with serpentine drive belt have reverse rotating fans and viscous fan drives. They are marked with the word REVERSE to designate their usage. Installation of the wrong fan or viscous fan drive can result in engine overheating.
CAUTIONIf 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 results 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.

If the fan assembly free-wheels without drag (the fan blades will revolve more than 5 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 will also ensure against excessively high coolant temperature.

  1. Drill an 1/8' ('3.18 mm) diameter hole in the top center of the fan shroud.
  2. Obtain a dial thermometer with a 8.0" stem (or equivalent). It should have a range of 0-220°F (-18-105°C). Insert thermometer through the hole in the shroud. Be sure that there is adequate clearance from the fan blades.
  3. On gasoline models, connect a tachometer and an engine ignition timing light. The timing light is to be used as a strobe light.
  4. On all models, block the air flow through the radiator. Secure a sheet of plastic in front of the radiator (or air conditioner 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 10 minutes, the air temperature (indicated on the dial thermometer) should reach 190°F (88°C). Fan drive engagement should have started to occur at 165-180°F (74-82°C). 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 (non-diesel only).
  7. When the air temperature reaches 190°F (88°C), remove the plastic sheet. Fan drive disengagement should have started to occur at between 135-175°F (57-79°C). A definite decrease of fan flow noise (roaring) should be noticed. If not, replace the defective viscous fan drive unit.

COOLING FAN (DIESEL)

CAUTIONIf the viscous fan drive is replaced because of mechanical damage, the cooling fan blades should be inspected. Inspect for fatigue cracks, loose blades, or loose rivets that could have resulted from excessive vibration. Replace the blade assembly is any of these conditions are found. Also inspect water pump bearing and shaft assembly for any related damage due to a viscous drive malfunction.
CAUTIONSome engines equipped with serpentine drive belts have reverse-rotating fans and viscous fan drives. They are marked with the word REVERSE to designate their usage. Installation of the incorrect fan or viscous fan drive can result in engine overheating.

Removal

  1. Disconnect both negative battery cables at both batteries.
  2. Remove the fan shroud mounting bolts. Position fan shroud toward engine.
  3. The thermal viscous fan drive/fan blade assembly is attached (threaded) to the fan hub shaft. (Scheme 2) Remove the fan blade/fan drive assembly from fan pulley by turning the mounting nut clockwise (as viewed from front). Threads on the viscous fan drive are LEFT HAND. Using appropriate fan wrench, loosen viscous drive assembly. Place a bar or screwdriver between the fan pulley bolts to prevent pulley from rotating while loosening viscous drive.
  4. Remove the fan shroud and the fan blade/viscous drive as an assembly from vehicle.
  5. Remove fan blade-to-viscous fan drive mounting bolts.
  6. Inspect the fan for cracks, loose rivets, loose or bent fan blades.

Installation

To install, reverse removal procedure. Tighten fan blade assembly-to-viscous drive bolts to specification. See TORQUE SPECIFICATIONS . Install viscous fan drive assembly on fan hub shaft and tighten to specification.

Note. Viscous Fan Drive Fluid Pump Out Requirements: After installing a new viscous fan drive, bring the engine speed up to approximately 2000 RPM and hold for approximately two minutes. This will ensure proper fluid distribution within the drive.

COOLING FAN (GASOLINE)

CAUTIONIf 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 viscous fan drive malfunction.
CAUTIONSome engines equipped with serpentine drive belts have reverse-rotating fans and viscous fan drives. They are marked with the word REVERSE to designate their usage. Installation of the incorrect fan or viscous fan drive can result in engine overheating.
  1. Disconnect negative battery cable from battery.
  2. Remove throttle cable at top of fan shroud.
  3. On models equipped with 8.0L engine, remove 3 coolant reserve/overflow tank mounting screws.
  4. On all other models, unsnap coolant reserve/overflow tank from fan shroud and lay aside. The tank is held to shroud with T-shaped slots. DO NOT disconnect hose or drain coolant from tank.
  5. On all models, the thermal viscous fan drive/fan blade assembly is attached (threaded) to water pump hub shaft. (Scheme 1) Using appropriate fan wrench, remove fan blade/viscous fan drive assembly from water pump by turning mounting nut counterclockwise as viewed from front. Threads on viscous fan drive are RIGHT HAND. Place a bar or screwdriver between water pump pulley bolts to prevent pulley from rotating. (Scheme 1)
  6. DO NOT attempt to remove fan/viscous fan drive assembly from vehicle at this time.
  7. DO NOT unbolt fan blade assembly from viscous fan drive at this time.
  8. Remove 4 fan shroud-to-radiator mounting bolts.
  9. Remove fan shroud and fan blade/viscous fan drive assembly as a complete unit from vehicle.
  10. 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.
  11. Remove 4 bolts securing fan blade assembly to viscous fan drive. (Scheme 1)

Install reserve/overflow tank to fan shroud. On 8.0L models, tighten screws to 50 INCH lbs. (6 N.m). On all other models, snap reserve/overflow tank into position. To complete installation, reverse removal procedure. Tighten fan and viscous drive assembly to specification. See TORQUE SPECIFICATIONS .

Note. Viscous fan drive fluid pump-out requirements: After installing a new viscous fan drive, bring the engine speed up to 2000 RPM and hold for approximately 2 minutes. This will ensure proper fluid distribution within the drive.

TORQUE SPECIFICATIONS

ApplicationFt. Lbs. (N.m)
Fan Blade Assembly-To-Viscous Fan Drive17 (23)
Viscous Fan Drive-To-Hub Shaft42 (57)

TORQUE SPECIFICATIONS