Belt area grinding noise

SONJUSTIN

MEMBER
2009 SCION XB
4 CYL
2WD
AUTOMATIC
200,000 MILES

At first, it was just a squeaking noise on first start up of the day for briefly 2 seconds. Then only later in the day if I had my AC or heat on. I'd turn the AC or heat off and the squeak would cease to exist. Only while slowing down too the squeak would come back. I was driving the other night and hit a puddle in a Taco Bell parking lot going no faster than 5. It was a pretty big puddle though since it was raining the past couple of hours. Immediately after a grinding noise came about. Now there's no more squeaking at all so the problem got worse. I ended up changing the alternator, AC pulley, and the belt. Power was flickering at night and no more now, the AC blows cold now with out it going straight to warm so I know I did something good. The grinding noise is still there and I can't tell which pulley to get because I need a labeled diagram that's no longer on my hood. May I have a diagram that has labels so I can figure his out?

Wednesday, December 10th, 2025 AT 9:17 PM

1 Reply

STEVE W.

MECHANIC
15,268 POSTS

Intermittent squeak like that would commonly be from the belt and tensioner assembly. Grinding noises are typically bad bearings. The fastest way to find those is with an automotive stethoscope. Very inexpensive tool shown in the image. To locate the offender you just start the engine and move the tip of the probe to each rotating parts bolts or the retainer bolt and listen. A good bearing will just have a light hum. A bad one will sound like a mixer filled with gravel! The diagram will show the various parts but the stethoscope would tell you which is the problem as they all have bearings. The letters indicate the item driven. A-Alternator, I-Idler pulley, T-Tensioner, P-Water Pump, C-Crankshaft, AC-Compressor. The idler and tensioner pulleys are common items for failure but the stethoscope would pinpoint the issue in seconds.

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