new serpentine belt and stretching?

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badtlc

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Sorry for the dumb question, but is it possible for a brand new serpentine belt to stretch a bit after a couple days of first use? The new belt made zero noises after it was first installed for a day. Then after a 2 or so days it started to sound like it was slipping a bit but not a chirping or high pitched squealing sound.

Thanks for any input.
 
Did you replace the belt tensioner pulley? Because belts can/do stretch...thats the job of the tensioner to keep a constant, pre-determined load on the belt. Better for your accessory bearings too.
 
Believe it or not, some newer vehicles have stretch on belts and no tensioner. If they are stretched too far, or are ever taken off, they will come off. They can only be stretched once. Maybe check to see if you have one of these?
 
Does the vehicle in question have manually adjustable belts, or an automatic tensioner? If it's the former, then yes, belts do stretch and break in and need re-tightening. Automatic tensioners do this automatically.
 
I'm not sure on the specifics. It is a 2007 Escape 2.3L and the idler pulley was replaced at the same time.
 
It takes a while for the rubber grooves to settle on the pulleys. More of a break-in than a stretch, but because it fits more snugly, there is a little circumference left over.

I suspect your tensioner. Should be fairly hard to grab a straight stretch of belt and twist it around with your fingers.

Or the belt is too (/properly) tight and you have a bearing complaining.
 
Originally Posted By: eljefino
It takes a while for the rubber grooves to settle on the pulleys.


That's something I was surprised to learn about when visiting the Dayco rubber products site. They said the ribs on the belt are suppose to ride ON the grooves of the pulleys ... not IN the grooves of the pulleys. They said that if the belt rides down IN the grooves, it's worn out. I did a double-take after reading that.
shocked2.gif
 
Originally Posted By: Merkava_4
Originally Posted By: eljefino
It takes a while for the rubber grooves to settle on the pulleys.


That's something I was surprised to learn about when visiting the Dayco rubber products site. They said the ribs on the belt are suppose to ride ON the grooves of the pulleys ... not IN the grooves of the pulleys. They said that if the belt rides down IN the grooves, it's worn out. I did a double-take after reading that.
shocked2.gif



That doesn't quite make sense. The belt rib has to ride in the sheave groove. It is only supposed to have contact on the belt/sheave sides....not the bottom/top.

Someone correct me if I am wrong. The picture on the right is better in that it shows a "gap" at both the top and bottom.


3257.gif
mufp_0711_02_z+engine_belt_fit_and_alignment+belt_diagram.jpg
 
Originally Posted By: doitmyself


That doesn't quite make sense. The belt rib has to ride in the sheave groove. But, I think it is only supposed to have contact on the belt/sheave sides....not the bottom/top.

Someone correct me if I am wrong.

3257.gif



No......I'm talking about ribbed belts. You're taliking about V-belts.
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Isn't a serpentine belt similar in shape to a v belt at the contact areas? The bottom picture (from Dayco)tells all.

belt.jpg
serpentine.gif

dy6071161.jpg
 
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Originally Posted By: doitmyself
Isn't a serpentine belt similar in shape to a v belt at the contact areas?


Yes, but it's not supposed to wedge its way down deep into the pulley like on a V-belt.

They're saying the belt in Figure C is worn out.
21.gif


daycobelts.png
 
Quote:
Yes, but it's not supposed to wedge its way down deep into the pulley like on a V-belt.


My one picture of the V belt is a bit off. V belts are not supposed to touch on the top/bottom either.... in most cases, the top of the V belt should protrude above the pulley and definitely should not bottom out.
pic018.gif



We are in agreement, I think! IMO (vs. their verbage "ON") the belt ribs DO ride IN the sheave groove. They are only supposed to have contact on the sides of the "V", not on the top and/or bottom.

I think the only thing we disagree on is the semantics of "in" vs. "on" regarding how the belt rides on the sheave (pulley).

Now, lets argue about sheave vs. pulley
07.gif


Have a good day.
 
Originally Posted By: justinf89
Believe it or not, some newer vehicles have stretch on belts and no tensioner. If they are stretched too far, or are ever taken off, they will come off. They can only be stretched once. Maybe check to see if you have one of these?


Never seen these,can you provide vehicle make engine? VW used a V belt with no "normal" tensioner but instead used a 2 piece pulley with shims in the middle.
Shims were added or removed to achieve correct tension.

I learned you never pry a belt on or twist it with force as you risk damaging the cords in the belt.
 
Thanks for all the good info. I just wish I knew how to do this myself and use the knowledge. I would use my normal mechanic who installed the belt, idler pulley and alternator but he is about 2 hours away.

The local NTB said they would tighten it if necessary for free. I guess I'll give them a shot. It definitely doesn't sound like a bearing noise or something under stress. It sounds like something is more loose than it was and there is a very faint scent of burning rubber. I really think the belt is just slightly loose now, but it definitely wasn't loose right after the replacement. It was perfectly quite for the first day or 2. But if I do have an automatic tensioner then maybe it needs replaced, too? That probably won't be cheap.
 
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I didn't do the work. I just heard back from my mechanic. He said there is no way the belt stretched. It must have an automatic tensioner. I'm guessing the tensioner is now bad unless it is something completely unrelated to the serp belt, but I can't see that being the case.
 
Mechtech, I've had a belt that stretched after 11 years and 60K, and reached the limit of the tensioner. When I compared the new belt with the old one there was a definite change in length.
 
Originally Posted By: mechtech2

How did you clean the pulleys first? Oh, you didn't?


Mechtech, how do you clean the pulleys? I've got CRC belt dressing
all over mine and I want to get that stuff off before I install a new belt.
 
I don't see actual belt stretch with modern belts. Timing or serpentine.
But sure, of course it can happen.

As to cleaning the pulleys, I was making a point to check them. It often is not necessary to actually clean them..
But a good check [at least] is. Material can build up on smooth pulley surfaces, and grooves can get hard build up as well. This is worse when it is irregular build up.
Wire brushing with a power tool [drill, etc] is easiest, if you need it.
 
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