Belt noises

well, about 1000 miles ago I replaced belts, pulleys, etc.
Now, it's making screeching / squealing noises.

Was fine until recently.
It's not constant, just random. Every time I drive it happens though, but it isn't a constant noise it stops and comes back. It's only when I accelerate, have foot on gas, or let off the gas as well.
Any ideas on what it could be?
Thanks.

 

belts are too loose.... I would start there.

 

How tight / loose are these belts supposed to exactly be? I'll start from there.

 

I would make them just tight enough to stop the squeaking.

 

Yes but how do I know if they're too loose? I don't want to make the belts too tight either.

 

If you hear squealing, then at least one is too loose. The dealers use a special tool to measure tightness. You're right about not being too tight, that could eventually cause bearing damage.

I would check each belt to determine the loosest one, then tighten that a bit.
Test it.
Repeat until squeals are gone.

Or, take it to a shop ($90 per hour labor charge), and have them do it.

 

I wasnt paying enough attention at the aftermarket shadetree parts counter and the kid gave me the right size belts but wrong pitch for the grooves. Some belts have 5 or even 7 grooves , mine have 4, he gave me the five.
I kept trying different adjustments for weeks until I finally noticed it
changed back the right belts and it has been solved

 

My standard (which has worked for 40 years) is to push on the belt , it should have about 3/8" to 1/2" slack. 1/2" or more slack is too much,under 1/4" is not enough.
As judged by the "eyeball ruler", "bubble level in butt", "torque intuition wrench" method.
You could put a straightedge across and measure the gap with a ruler but I trust the eyeball ruler just as well myself
Belt slack indicator tools are available but my system has been working for me and I cant justify buying the tool for the amount of belt changing I do.

keep in mind that looser is safer ; the worse can happen is annoying noise
tight can overheat the belt and or cause bearing damage

 

That did not fix it. Any ideas?

 

What exactly did you do, that did not fix it?

Also, are you certain its the belts and not something else?

 

Tried tightening them.

I'm certain it's the belts.

Also, it's only when accelerating / letting off gas (when I hit brakes the noise stops?)
Everything is new as well.

 

have a friend rev engine while you listen for the squeak under the hood. use a paper towel cardboard sleeve as a tube over your ear to pinpoint the noise location. then see if its the belts or the pulleys squeaking. you could have a bad pulley bearing, even on a new one

 

It does not do it while in park.

 

then its not your belts or pulleys, if it were that, then it should do it anytime and not need to be in gear.

it might be your throwout bearing doing it if its a manual tranny or if its an auto, then maybe drivetrain related

 

I have a very similar issue. i hear squeaking when driving from 30-50mph. but the noise isn't consistant with the RPMs, just the velocity. and its kinda random. I greased my u-joints and the noise went mostly away. still slightly there though.

figured this by driving til the squealing started, and putting my truck in neutral and coasting. the engine went idle, the squealing continued. i believe it's my center support. i have a bit of play in it so tomorrow (monday) I'm going to replace it with my buddy.

also, the noise got worse after I changed my tranny mount a couple weeks ago. I guess the tranny sitting lower kept the driveshaft held down so it wouldn't move. but now that it's at the correct ride height, the center support can flop around more, rubbing against it's own metal cage causing the squealing.

luckily I have a 4x4, so peeps tell me I can just remove the rear driveshaft, put it in 4x4, and drive it like it's a front wheel drive truck :-D

 

I can see a tad bit of oil on a pulley. Could this be causing it?

I need to replace valve cover gasket.