Fan belt squeak - allegedly

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Posting for my daughter so the details are a bit sketchy ............

Her MK has a squeak that appears to be belt/pulley origin.

She tells me that "three pulleys and the belt have been changed" but that the squeak persists. Apparent at idle and upon acceleration.

Any words of wisdom to help resolve the issue?

[Kingbrown]

Alternator bearings &/or brushes ?
IIder or tensioner bearings ?
Airconditioner clutch bearing ?

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Rub a little bar soap on the belts this will take any belt squeak away do it one at a time till you find the squeaky belt.
This may fix the problem for a while

[Kingbrown]

Try loading up the alternator by switching on lots of electrical load (fan on high, aircon, headlights, brake lights). If the squeak changes tone with the extra load then it could help in narrowing down the source of the squeak.

To deliver a particular amount of power from driven equipment at low engine speed will require more torque (belt load) than it does at high speed. Hence why loose belts often squeal when starting the engine or when accellerating (ie alternator and aircon belts).

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Thanks for the replies. I've passed them on.