Dodge Durango (DN) 1998-2003 Service Manual » Cooling System » Diagnosis and testing »

Viscous fan drive. Accessory drive belt diagnosis

Viscous fan drive

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.

WARNING: BE SURE THAT THERE IS ADEQUATE FAN BLADE CLEARANCE BEFORE DRILLING.

(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 105C (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 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.

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.

(6) Start the engine and operate at 2400 rpm.

Within ten minutes the air temperature (indicated on the dial thermometer) should be up to 88 C (190 F).

Fan drive engagement should have started to occur at between 74 to 82 C (165 to 180 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 88 C (190 F), remove the plastic sheet. Fan drive disengagement should have started to occur at between 57 to 79 C (135 to 175 F). A definite decrease of fan flow noise (roaring) should be noticed. If not, replace the defective viscous fan drive unit.

Accessory drive belt diagnosis

VISUAL DIAGNOSIS

When diagnosing serpentine accessory drive belts, small cracks that run across the ribbed surface of the belt from rib to rib (Fig. 23), are considered normal.

These are not a reason to replace the belt. However, cracks running along a rib (not across) are not normal.

Any belt with cracks running along a rib must be replaced (Fig. 23). Also replace the belt if it has excessive wear, frayed cords or severe glazing.

Refer to the Accessory Drive Belt Diagnosis charts for further belt diagnosis.

NOISE DIAGNOSIS

Noises generated by the accessory drive belt are most noticeable at idle. Before replacing a belt to resolve a noise condition, inspect all of the accessory drive pulleys for alignment, glazing, or excessive end play.

Fig. 23 Belt Wear Patterns Fig. 23 Belt Wear Patterns

1 - NORMAL CRACKS BELT OK

2 - NOT NORMAL CRACKS REPLACE BELT

ACCESSORY DRIVE BELT DIAGNOSIS CHART

CONDITION POSSIBLE CAUSES CORRECTION
RIB CHUNKING (One or more ribs has separated from belt body) 1. Foreign objects imbedded in pulley grooves.

2. Installation damage

 1. Remove foreign objects from pulley grooves. Replace belt.

2. Replace belt
RIB OR BELT WEAR 1. Pulley misaligned

2. Abrasive environment

3. Rusted pulley(s)

4. Sharp or jagged pulley groove tips

5. Belt rubber deteriorated

 1. Align pulley(s)

2. Clean pulley(s). Replace belt if necessary

3. Clean rust from pulley(s)

4. Replace pulley. Inspect belt.

5. Replace belt
BELT SLIPS 1. Belt slipping because of insufficient tension

2. Belt or pulley exposed to substance that has reduced friction (belt dressing, oil, ethylene glycol)

3. Driven component bearing failure (seizure)

4. Belt glazed or hardened from heat and excessive slippage

 1. Inspect/Replace tensioner if necessary

2. Replace belt and clean pulleys

3. Replace faulty component or bearing

4. Replace belt.
LONGITUDAL BELT CRACKING 1. Belt has mistracked from pulley groove

2. Pulley groove tip has worn away rubber to tensile member

 1. Replace belt

2. Replace belt
9GROOVE JUMPING" (Belt does not maintain correct position on pulley) 1. Incorrect belt tension

2. Pulley(s) not within design tolerance

3. Foreign object(s) in grooves

4. Pulley misalignment

5. Belt cordline is broken

 1. Inspect/Replace tensioner if necessary

2. Replace pulley(s)

3. Remove foreign objects from grooves

4. Align component

5. Replace belt
BELT BROKEN (Note: Identify and correct problem before new belt is installed) 1. Incorrect belt tension

2. Tensile member damaged during belt installation

3. Severe misalignment

4. Bracket, pulley, or bearing failure

 1. Replace Inspect/Replace tensioner if necessary

2. Replace belt

3. Align pulley(s)

4. Replace defective component and belt
NOISE (Objectionable squeal, squeak, or rumble is heard or felt while drive belt is in operation) 1. Incorrect belt tension

2. Bearing noise

3. Belt misalignment

4. Belt to pulley mismatch

5. Driven component induced vibration

 1. Inspect/Replace tensioner if necessary

2. Locate and repair

3. Align belt/pulley(s)

4. Install correct belt

5. Locate defective driven component and repair
TENSION SHEETING FABRIC FAILURE (Woven fabric on outside, circumference of belt has cracked or separated from body of belt) 1. Tension sheeting contacting stationary object

2. Excessive heat causing woven fabric to age

3. Tension sheeting splice has fractured

 1. Correct rubbing condition

2. Replace belt

3. Replace belt
CORD EDGE FAILURE (Tensile member exposed at edges of belt or separated from belt body) 1. Incorrect belt tension

2. Belt contacting stationary object

3. Pulley(s) out of tolerance

4. Insufficient adhesion between tensile member and rubber matrix

 1. Inspect/Replace tensioner if necessary

2. Replace belt

3. Replace pulley

4. Replace belt

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