Late model Kia 3.5L V6 engines such as those in Sedona minivan, Sorendo and other models may develop a buzzing, whining or growling noise from the engine compartment. If the noise is coming from near the serpentine belt and pulleys, the cause is often bad bearings in the serpentine belt idler pulley (color coded orange in the images below).
After tens of thousands of miles of use, the shaft bearings inside the idler pulley become worn causing a vibration that produces a loud noise. Similar noises can also be caused by bad shaft bearings on the water pump, alternator, belt tensioner pulley or power steering pump pulley. But in most cases, the cause of the noise is a bad idler pulley.
Other possible causes of pulley noise can be ruled out by removing the belt and rotating each pulley by hand. If any pulley wobbles, feels loose or feels rough or binds when it is spun by hand, it could also be a source of noise and should also be replaced. Coolant leaks around the water pump would indicate a bad seal and shaft bearings in the pump.
WARNING! Don't ignore the noise because it will progressively get worse, and ultimately the idler pulley may seize or break loose. If this happens, it will throw the serpentine belt off the pulleys or snap the belt causing a loss of engine cooling, alternator output, A/C cooling and power steering assist. Stop driving immediately and have your Kia towed to a service facility for repairs. Driving without the belt in place will cause the engine to rapidly overheat, which may damage the head gaskets or scuff the pistons.
The fix for the idler pulley noise problem is to replace the idler pulley. A new idler pulley will cost you about $40 and can be installed in 15 to 20 minutes.
To replace the idler pulley, use a breaker bar and 19mm socket to rotate the automatic tensioner pulley counterclockwise toward the crankshaft pulley. There is a hex head fitting just under the automatic tensioner pulley for rotating the pulley (color coded green in the illustration).
Once belt tension has been relieved, you can slip the belt off the pulleys. Inspect the belt for wear or damage, and replace as needed. The service life of the original equipment serpentine belt is about 100,000 miles, but some belt may need to be replaced sooner if the V-grooves on the underside of the belt are worn, or the belt has been contaminated with grease or oil.
Remove the black plastic cap that covers the mounting bolt on the idler pulley. This cap snaps into place and can be easily pulled off with channel lock pliers or pried off with a small screwdriver. Once the cap is off, you can loosen and remove the bolt that holds the idler pulley in place.
If the bearings inside the idler pulley are bad, there may be some noticeable wobble in the pulley as it rotates or roughness. The pulley bearings are sealed for life and cannot be disassembled for inspection or relubricated. If worn, the idler pulley must be replaced with a new pulley. It only takes a small amount of wear in the idler pulley bearings to produce a LOT of noise.
Install the new pulley and tighten the mounting bolt (about 43 ft. lbs. is recommended). Then replace the plastic cap because it helps keep dust and water out of the bearing.
Now comes the tricky part. Carefully route the serpentine belt around all of the pulleys as shown in the illustration, leaving the idler pulley for last. Make sure the belt is centered on all of the pulleys and that the V-grooves line up with the grooves in the pulleys. Use the pry bar to rotate the tensioner pulley clockwise toward the crankshaft pulley again so you gain enough clearance to slip the belt over the idler pulley. Once the belt is in place, allow the tensioner to rotate back to its normal position so it can apply pressure to hold the belt tight.
Recheck the alignment of the belt, remove all tools from the engine compartment then start the engine. The noise should be gone and you should be good to go!