Jeep: Tapping Sound After Engine Warm Up

Jeep: Tapping Sound After Engine Warm Up

Some customers may ­experience a tapping sound from the engine compartment after ­engine warm up. This bulletin involves the ­installation of a serpentine drive belt and a new design idler pulley using a revised belt routing. MODELS: 2007–'08 (KA) Nitro

MODELS: 
2007–‘08 (KA) Nitro
NOTE: This bulletin applies to models equipped with
the 4.0L engine.
Some customers may ­experience a tapping sound from the engine compartment after ­engine warm up. This bulletin involves the ­installation of a serpentine drive belt and a new design idler pulley using a revised belt routing.

Fig. 1 Revised Belt Routing 1 - Upper Idler Pulley 2 - Driver Side Idler Pulley 3 - Passenger Side Idler Pulley

Diagnosis:
1. Start engine and allow it to idle for five minutes in order to bring the accessory drive components to operating temperature.
2. Set the HVAC to windshield defrost mode. Set the temperature to its coldest setting, and turn on the A/C. While maintaining an engine speed ­between 1,800 and 2,000 rpm, listen for tapping sound. If a tapping sound is evident, shut the engine off. Remove the serpentine drive belt following procedures found in DealerCONNECT. Do not let the tensioner arm snap back to the free position as damage may occur to the tensioner.
3. Restart the engine and listen for a tapping sound. If there is a tapping sound, this bulletin does not apply and additional diagnosis is required. If there is not a tapping sound, perform the repair procedure.
Repair Procedure:
1. Remove idler pulley (No. 1 in Fig. 1).
2. Install the new idler pulley and serpentine drive belt using the ­revised routing (Fig. 1).
Courtesy of Identifix

You May Also Like

Alternator Testing For No Charge Conditions

Many alternator problems turn out to be nothing more than a bad connection at the alternator or a bad wiring harness.

If only battery voltage is present at the battery on a running engine, does this mean the alternator is “bad?” No, it does not. It only means that the alternator is not charging, but does not reveal why. Therefore, it does not point to a faulty alternator. All too often, the alternator is condemned by technicians due to this test alone. The cause could instead be a module that distributes the power to the vehicle and regulates the alternator.

Understanding Coolants

All-season coolant used inorganic acid technology and worked great for almost 30 years.

Ignition System Do’s and Don’ts

Why do ignition systems give technicians problems when diagnosing ignition-related misfires? The answer is that some technicians use tests that might give inconclusive results or do damage to the coil or drivers inside a module.

Tools To Service Serpentine Belts

Servicing the serpentine belt on some vehicles is a tough task.

Battery Charging and Diagnostics

Here are six tips to use when diagnosing a vehicle with a dead battery. 

Other Posts

Why Does Engine Coolant Need Replacement?

Two specifications can be used to justify replacement — the condition of the additive package & the freezing point.

Engineering Better Belt Systems

An accessory drive belt is always both speeding up and slowing down.

Why Do Timing Chains Stretch?

As the timing chain wears, it can change the timing of the camshaft and crankshaft.

Carbon Deposits and Direct Injection Engines

The primary cause of these problems is that fuel and added detergents are not hitting the back of the intake valves.