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Discussion Starter · #1 ·
1995 6.5 in a P30 step van. My serpentine belt squeaks or chirps. It starts chirping when I start it, and it will get quiet after 25 miles, or so. Noise more obvious at idle, but I can still hear it at highway speed. It will go quiet instantly with a tiny squirt of WD40 or silicone spray, but the noise always comes back. Belt has less than 15K miles on it. Old belt did the same thing, and so did the one before that. Current belt is a Dayco, and so was the last one. Will be quiet if I drive next day, but noisy if I let it sit a week.

Everything loos to be lined-up fine, and I see no strange wear patterns on belt. Pretty sure it is the belt slipping on some pulley, and not a pulley bearing because the WD40 makes it quiet with just a small spray.
 

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I apply a bar of soap on the SERP belt edge and it takes away any squeaks..
 

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The tensioner may be weak.
 

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I just went through this with my 4cyl Tacoma. Actually, been going through it. One by one for the past couple of years I have replaced all idler pulleys and the tensioner and the belt. With each replacement the chirp went away. And then came back days, weeks, months later. I've used a stethascope and a megaphone to try and isolate where it is coming from. Placed a straight edge across all pulleys to check for alignment. Washed and dryed all mating surfaces, including the belt. Now, hang on to your hats...

Wife said to me "what if you put oil on the belt." Of course I commenced to instructing her how that is never a fix and don't ever put anything, especially oil, on a belt. And then.... The homemade megaphone of a large screwdriver and the top half of a cut in half washer fluid bottle found the spot. It's the backside of the belt where it meets one of the idlers closest to another pulley, the ps. None of the pulleys are adjustable for alignment. So? You guessed it. With nothing to lose, I coated the backside of the belt and the smooth side of the pulleys with silicone spray from WD40. It stopped chirping. That was months ago. We shall see if and when it comes back.

The reality seems to be that the ps pulley is out of alignment with the idler nearest it causing the belt to slide across the idler enough to chirp. Why does it come and go with each "fix"? Idk. But so far, it has not come back with this greasing of the belt and there is nothing I can do to align the ps pulley. Posts indicate it is pressed on and you either get lucky or you don't that it will be straight. That I can actually cause more harm trying to pull it off and put it back on. I don't even know how I would assure it were perfect if I tried. Toyota didn't.

So, Still Bill, I suggest you replace one by one each ilder and the tensioner. Wait after each. Observe. If this does not do it, go where no man should ever go - lube on the non friction side of the belt. And if you want brownie points, let the wife suggest it first ;-)
 

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Did you check to make sure all the pulleys are good?
Make sure the alternator bearing is good?
Make sure everything sorrounded by the pulley are good?
What belt did you put in 15k miles ago? If it is the belt, buy the green Gates HD belt that is better than most.
 

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W
 

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Alternator pulley might be worn from the tensioner being weak. A serpentine belt is just a series of very belts, once the vee bottoms out and no longer wedges between the grooves, it squeaks. I see it a lot with heavy equipment, the dusty environment eats the grooves away.
 

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Discussion Starter · #9 ·
Haven't had time to work on it yet, since it is (for now) just an annoyance. But, I did say in original post that 1 drop of WD40 shut it right up. Good thought about stethoscope - rubber hose should work for that. Maybe scuff idler or tensioner pulley with 600 grit sandpaper?
 

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Haven't had time to work on it yet, since it is (for now) just an annoyance. But, I did say in original post that 1 drop of WD40 shut it right up. Good thought about stethoscope - rubber hose should work for that. Maybe scuff idler or tensioner pulley with 600 grit sandpaper?
Man, my CRS is bad. Yep, I forgot to mention that. It was actually the rubber hose that nailed it down. The stethoscope indicated the tensioner, but not really. The megaphone indicated near the actual offending pulley and the rubber hose nailed it. Hey, this was months ago and I've been on covid beer time for awhile ;-)
 
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The crank pulley is also a possibility. When the rubber in them starts to go they make noises under load. The alternator will pull for the first 15-20 minutes after startup. My 1st guess would be the tensioner. Thee internal plastic bushings in them wear and bind. That will inhibit the tensioner from doing it's job. Usually by the time the bearing in the tensioner pulley is starting to get loose, the tensioner is shot. If the tensioner gets let go too long it can bind in over tight. That will take out the bearings in all the accessories and the crank pulley.
 
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