Serpentine belt squeaking

GAPY1

MEMBER
2004 FORD F-150
5.4L
V8
4WD
AUTOMATIC
121,000 MILES

Replaced numerous pulleys and the belt tensioner. Had to replace the serpentine belt numerous times in the last 6 months due to squeaking. As soon as I put a new belt on the squeaking goes away and then it starts back up within in a couple of weeks and then is awful after a month. The squeaking subsides when the engine gets warmed up if the outside temperature isn't too cold. My mechanic has no clue why it keeps happening.

Monday, November 22nd, 2021 AT 9:05 AM

3 Replies

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

Hi,

If the tensioner is new, the belt is new, and nothing is leaking such as coolant or oil and getting on the belt, chances are one of the belt-driven pullies is dragging when cold.

First, confirm there is no contamination on the belt. If there isn't, before starting the vehicle and when it gets bad, remove the belt and spin each of the belt-driven pullies. See if there is excessive resistance. Also, keep in mind that the alternator places the heaviest load on the belt when first started. So, as a test, when it's making noise, turn all electric accessories on to see if the sound gets worse. If it does, suspect the alternator may be failing.

One last thought. Is there any evidence of damage to the ribs on the belt? Is it running straight fully on each of the pullies?

Let me know.

Joe

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Monday, November 22nd, 2021 AT 9:14 PM

GAPY1

MEMBER
2 POSTS

Thanks for the info. The alternator was replaced as well but it's been a few years. Is there a chance that one of the pulleys that were replaced could actually be the wrong size? If it was would it still fit? If so, maybe that's why each new belt keeps getting stretched out after a few weeks because when the belt is new there is no noise at all.

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Tuesday, November 23rd, 2021 AT 5:35 AM

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

Hi,

Absolutely if parts were replaced that came with a new pulley, it could be different. Remember, the automatic tensioner can only go so far before it bottoms out. After that, it can't tighten anymore. Also, the belt can be too long. I attached the original part number below and specifications for the one it should have. See if you can find your belt's part number and let's cross-reference it.

Also, confirm it is routed properly. See pic two for belt routing.

Let me know what I can do to help.

Take care,

Joe

See pic below.

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