Diesel Data: Automotive Repair

Component Tests and General Diagnostics

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 incorrectly 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.

NOTE: Do not apply any fluids or belt dressing to the belt or pulleys.

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, A C clutch engagement, 1-2 shift and power steering loading.

Drive belt squeal can occur under certain conditions:
^ 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 discharged and suction pressure that occurs after several minutes) exceeds specifications.
^ if any of the accessories are damaged, have a worn or damaged bearing, or internal torsional resistance above normal. All accessories should be rotatable by hand in the unloaded condition. If not, inspect the accessory.
^ if fluid gets on the drive belt. This includes power steering fluid, engine coolant, engine oil or air conditioning system lubricant. If excessive fluid does get on the drive belt during repair, install a new drive belt.
^ 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 indicator is outside the normal installation wear range window, install a new drive belt.

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

Install a new drive belt tensioner if the drive belt tensioner is worn or damaged.

Belt Tension

NOTE: Drive belt tension is not adjustable.

The drive belt tensioner automatically adjusts drive belt tension.

Belt Tensioner, Automatic
Check the automatic drive belt tensioner:
1. With the engine off, check for correct drive belt routing. Repair as necessary.
2. Rotate the drive belt tensioner and check for a binding or frozen condition. Install new components as necessary.

Drive Belt Misalignment

CAUTION: Incorrect drive belt installation will cause excessive drive belt wear and can cause the drive belt to come off the drive pulleys.





Non-standard drive belts can track differently or incorrectly. If a drive belt tracks incorrectly, install a new drive belt to avoid performance failure or loss of the drive belt.

With the engine running, check drive belt tracking. If the edge of the drive belt rides beyond the edge of the pulleys, noise and premature wear can occur. Make sure the drive belt rides correctly on the pulley. If a drive belt tracking condition exists, proceed with the following:
^ Visually check the drive belt tensioner for damage, especially the mounting pad surface. If the drive belt tensioner is not installed correctly, the mounting surface pad will be out of position. This will result in chirp and squeal noises.
^ With the engine running, visually observe the grooves in the pulleys (not the pulley flanges or the pulley forward faces) for excessive wobble. Install new components as necessary.
^ Check all accessories, mounting brackets and the drive belt tensioner for any interference that would prevent the component from mounting correctly. Correct any interference condition and recheck the drive belt tracking.
^ Tighten all accessories, mounting brackets, and drive belt tensioner retaining hardware to specification. Recheck the drive belt tracking.