Jeep Tech Tip: Tapping Sound After Engine Warm Up – UnderhoodService

Jeep Tech Tip: Tapping Sound After Engine Warm Up

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


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

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