Most of the time squeals are caused by bad pulley bearings and faulty tensioners. Tensioner assemblies themselves do go bad and not just their pullies. Sometimes they get sticky. This prevents them from applying proper tension at times. Sometimes they develop play. This causes the tensioner arm to walk in and out as it articulates back and forth.

However, sometimes belt squeals are caused by pulley misalignment. This will pretty much only be caused by power steering pumps with press on pullies. The pulley needs to be flush with the end of the pump shaft. If it's pressed in a little too far or not far enough then it'll put a lateral tension on the belt. This will cause glazing and a belt squeal. This squeal can be harder to diagnose because typically the noise of the squeal will be away from the power steering pump.




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