Under normal use, the serpentine drive belt should be inspected at around 45,000 miles or after 3-4 years of service. If not replaced at this time, the belt should be checked each additional year or 15,000 miles. Under severe and off-road conditions inspect the belt annually. When diagnosing serpentine drive belts, small cracks that run across ribbed surface of belt from rib to rib are considered normal. These are not a reason to replace the belt. However, cracks running lengthwise along a rib (not across) are not normal. Any belt with cracks running lengthwise along a rib should be replaced. Also replace the belt if it has excessive wear, frayed cords or severe glazing.
Warning: Spring tensioners should not be disassembled because of high spring tension. The tensioner unit is serviced as an assembly.
4.0 I-6 Engine:
4.0 Engine belt routing and tensioner release location
4.7 V-8 Engine:
4.7 Engine belt routing and tensioner release location
Belt removal and replacement:
NOTE: If anything differs between the pictures shown above and the Belt Routing Label (located in the engine compartment), use the schematic on the Routing Label.
CAUTION: DO NOT LET TENSIONER ARM SNAP BACK TO THE FREEARM POSITION, SEVERE DAMAGE MAY OCCUR TO THE TENSIONER. SLOWLY RELAX THE TENSION BACK TO THE STOP POSITION.
1. Disconnect negative battery cable from battery.
2. Using a 15mm socket wrench (1/2″ drive breaker bar or ratchet for the 4.0), rotate belt tensioner clockwise until it contacts its stop. Remove belt, then slowly rotate the tensioner into the freearm stop position.
3. Install new belt. Route the belt around all pulleys except the idler pulley. Rotate the tensioner arm clockwise until it contacts its stop position. Route the belt around the idler and slowly let the tensioner rotate into the belt. Make sure the belt is seated onto all pulleys. Inspect the entire belt path to make sure it is seated correctly on the pulleys.
4. With the drive belt installed, inspect the belt wear indicator (see diagram below):
On 4.7L engines, the tensioner is equipped with an indexing tang on back of tensioner and an indexing stop on tensioner housing. If a new belt is being installed, tang must be within approximately 24 mm (.94 inches) of indexing stop. Belt is considered new if it has been used 15 minutes or less.
On 4.0L Engines, the indicator mark must be between the minimum and maximum marks. The tensioner arm has three marks. Upon installation of a new belt, the double line marks close to each other should be very close to the mark on the base. The belt should be replaced if the single line mark lines up with the mark on the base.