Extraneous noises can often be heard when the engine is running. Very often problems are caused by belt drives of attachments. Squeaking (whistling) occurs as a result of belt wear or contamination (oiling). In addition, old belts can dry out and lose elasticity or become damaged. microcracks form on it, which, in turn, become clogged with accumulated dirt. This will cause the belt to slip on the pulley.
A defective belt must be replaced.
If the belt is dirty or no longer sufficiently elastic, use Verylube V-belt spray - spray for the care of drive belts on engine parts.