Drive Belt Noise/Flutter

Drive belt chirp occurs due to pulley misalignment or excessive pulley runout. It can be the result of a damaged pulley or an improperly aligned pulley.

To correct, determine the area where the noise comes from. Check each of the pulleys in that area with a straightedge to the crankshaft pulley. Look for accessory pulleys out of position in the fore/aft direction or at an angle to the straightedge.

Drive belt squeal is an intermittent noise that occurs when the drive belt slips on a pulley during certain conditions, such as: engine start up, rapid engine acceleration, or A/C clutch engagement.

Drive belt squeal can occur:
- if the A/C discharge pressure goes above specifications:
- The A/C system is overcharged.
- The A/C condenser core airflow is blocked.

- if the A/C off equalized pressure (the common discharge and suction pressure that occurs after several minutes) exceeds specification. Turn the A/C on for a few seconds and then off after the engine cooling fan motors begin to cool the A/C condenser core.
- if any of the accessories are damaged, or have a worn or damaged bearing or internal torsional resistance above the normal.
- Using a technician's stethoscope, check for noise at the idler pulley (4.0L Explorer, at the tensioner pulley bearing).

WARNING: DO NOT RUN THE ENGINE FOR MORE THAN 30 SECONDS WITH THE DRIVE BELT REMOVED.

- Remove the drive belt and start the engine. With the engine running, check to see if the noise is still present. If the noise is not present, replace the idler pulley.
- if fluid gets on the drive belt . This includes power steering fluid, engine coolant, engine oil or air conditioning system lubricant. If fluid does get on the drive belt during repair, clean the drive belt with soap and water and thoroughly rinse with clean water. Do not install a new drive belt if no apparent damage has occurred.

NOTE: The drive belt tensioner arm should rotate freely without binding.

- if the drive belt is too long. A drive belt that is too long will allow the drive belt tensioner arm to go all the way to the arm travel stop under certain load conditions, which will release tension to the drive belt. If the drive belt tensioner is resting on the stop. replace the drive belt.
- if the drive belt tensioner is worn or damaged.