What causes belt squeal on startup? - Forums at Modded Mustangs
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post #1 of 24 Old September 19th, 2011, 03:59 PM Thread Starter
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What causes belt squeal on startup?

Im sure some of you know, I always have belt issues. I recently put on a Dayco Poly rib 108" belt and a Dayco No slack tensioner. Seems to be working great. Hitting about 10-11psi in the cool weather.

Today I started it up (cold startup) and the belt squealed alittle on startup... Anyone know why? What causes it? Idler pulleys? Other pulleys (alt/water pump/AC?) Im going to check to see if any oil from the blower dripped on the belt. But it seemed to work fine after that, I couldnt really watch the boost gauge and road, but it looked like it was at 9psi before the shiftlight came on.

I just want to get any problems solved. I was going to buy a 3.12 pulley and 4 core intercooler so the blower wouldnt have to spin so fast to make 10psi and reduce the chance of belt slip, but my tuner wants $200 for a re-tune. Which seems like way to much for me. So I can't right now. Ill just save it for the winter.

Also, where can I buy replacement Vortech idlers? The 2 smoothe ones? Can I just buy 2 Ford idlers for a GT? I believe their the same size? I figure I might as well change those just to be safe. I have 18k on the blower setup. And probably 17k with the 2.87 pulley which is like 52,000rpm by 6300rpm.


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post #2 of 24 Old September 19th, 2011, 04:37 PM
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I'm not sure but I've had my share of belt problems and quite a few squeaky belts with my Procharger. The belt on there now likes to squeak until the engine is warm, very annoying.


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post #3 of 24 Old September 19th, 2011, 04:42 PM Thread Starter
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That might be a pulley. Usually the squeak will go away until the bearing warms up. If I had to guess, the tensioner pulley. Mine just squeaks on startup....which tells me its slipping or something. I just dont want to glaze the belt, and get belt slip. Belt slip sucks!


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post #4 of 24 Old September 19th, 2011, 04:44 PM
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When I was having my problems last month, I checked every pulley. All turned freely. When I got the pulleys aligned properly and the new belt on I had bad belt squeal when I first started the car. It went away after a few minutes. Spraying belt dressing on it just made it a lot worse. Operating the throttle from under the hood I noticed the tensioner jumping up and down a little. It never did that before. I changed it with one from Autozone and the belt squeal went away. My theory is that the spring in the stock tensor had gotten weak. It then expanded when it gets hot putting more pressure on the belt. Since you've already changed the tensioner, I don't know. It is possible that you got a bad one.

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post #5 of 24 Old September 19th, 2011, 04:49 PM Thread Starter
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I hope not. If so Ill just buy an OEM one. But like I said its just on startup. Its squeels real quick as the car starts up, but doesnt keep doing it.


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post #6 of 24 Old September 19th, 2011, 04:50 PM
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^ sounds alot like my problem eagle. I might have to swap my tensioner, did you have to grind on the new tensioner? I once ran into a problem where the tensioner had issues hitting the s/c bracket. I thought maybe my belt had glazed from slipping at the track, it's seen more track time this year than road time.


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post #7 of 24 Old September 19th, 2011, 04:52 PM Thread Starter
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Thats a good thought, Ill check to see if the guard is hitting the bracket. I dont think it is, but worth checking it out.


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post #8 of 24 Old September 19th, 2011, 04:58 PM
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Quote:
Originally Posted by MATT02GT View Post
^ sounds alot like my problem eagle. I might have to swap my tensioner, did you have to grind on the new tensioner? I once ran into a problem where the tensioner had issues hitting the s/c bracket. I thought maybe my belt had glazed from slipping at the track, it's seen more track time this year than road time.
Yes. My stock tensioner did not have a belt guard. The new one did and it hit against the ProCharger bracket. I went to four parts stores looking for one without the belt guard. They all had different designs but all had belt guards. I bought the one from Autozone because it looked like it would be the easiest to modify. I took the idler pulley off the tensioner and ground the belt guard down so that it actually is lower then the pulley wheel. It then fit perfect.

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post #9 of 24 Old September 19th, 2011, 07:13 PM
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Quote:
Originally Posted by Shaun03GT View Post
Im sure some of you know, I always have belt issues. I recently put on a Dayco Poly rib 108" belt and a Dayco No slack tensioner. Seems to be working great. Hitting about 10-11psi in the cool weather.

Today I started it up (cold startup) and the belt squealed alittle on startup... Anyone know why? What causes it? Idler pulleys? Other pulleys (alt/water pump/AC?) Im going to check to see if any oil from the blower dripped on the belt. But it seemed to work fine after that, I couldnt really watch the boost gauge and road, but it looked like it was at 9psi before the shiftlight came on.

I just want to get any problems solved. I was going to buy a 3.12 pulley and 4 core intercooler so the blower wouldnt have to spin so fast to make 10psi and reduce the chance of belt slip, but my tuner wants $200 for a re-tune. Which seems like way to much for me. So I can't right now. Ill just save it for the winter.

Also, where can I buy replacement Vortech idlers? The 2 smoothe ones? Can I just buy 2 Ford idlers for a GT? I believe their the same size? I figure I might as well change those just to be safe. I have 18k on the blower setup. And probably 17k with the 2.87 pulley which is like 52,000rpm by 6300rpm.
I've read a few reviews that the Dayco belts squeal. I've got a 107" Dayco Poly that I got with my 3.12 pulley, but still contemplating on if I should use it next year when I through the intercooler and pulley on or get a Gates and keep the Dayco as a spare. The Dayco does seem like it is much harder rubber and not as stickly as the 108" Gates I have on the car now.


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post #10 of 24 Old September 19th, 2011, 09:19 PM Thread Starter
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107" for a 3.12 is way to small. 107.5" will be better, even then I run a 108" on this 2.87.

Thats good to hear though I guess. I just hope it doesnt keep doing it and glaze the belt so it slips.


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post #11 of 24 Old September 19th, 2011, 09:59 PM
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Quote:
Originally Posted by Shaun03GT View Post
107" for a 3.12 is way to small. 107.5" will be better, even then I run a 108" on this 2.87.

Thats good to hear though I guess. I just hope it doesnt keep doing it and glaze the belt so it slips.
The guy I bought the pulley and belt from ran it on his 03 GT without a problem and no belt slip. If I do get a Gates it will probably be a 107.13" part number K061066. I don't know how you run such a big belt on a pulley that small. The 108" K061080 Gates is actually 108.75". I've read of guys just stepping down to a 3.33" and getting one size shorter belt which would be K061075 108.12" and it fit perfectly.


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post #12 of 24 Old September 19th, 2011, 10:41 PM Thread Starter
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Anytime I run smaller then a 108" belt, I toss a rib on the belt. And it wears out the tensioner


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post #13 of 24 Old September 20th, 2011, 10:19 AM
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this is what i did to make sure i was not beating up tensoners and pulleys. i ran the oem tensoner and cut the stop off the back this allowed for the tensoner to get drawn back farther and keep a tighter belt. be sure you dont get to tight of a belt or else the belt will hit the bottom of the tensoner. another thing to try is to start the car with the ac on, sometimes that pulley goes bad.


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post #14 of 24 Old September 20th, 2011, 01:10 PM Thread Starter
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When ever I get on the car with the ac it'll squeal until the car is at full operating temp. I might try cutting the stop on the tensioner. Would that allow me to run a little smaller of a belt? Anytime I run a 107.5 it tears.


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post #15 of 24 Old September 20th, 2011, 01:21 PM
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cutting the stop has always allowed me to run about a 1/2 inch smaller belt without issues. im not sure if it was just my car but the 108 belt was so damn small. i could not get it on a 3.33 pulley without the stop cut. once i got to the 3.0 pulley it was still sitting slightly past the stop once i had cut it. our tensoner relaxes as you rev the motor so the tighter your belt is the less chance for belt slip under load.


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post #16 of 24 Old September 20th, 2011, 03:28 PM
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Had same problem but I'm NA, was my idler and tensioner pulley..cheap, quick fix =]

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post #17 of 24 Old September 20th, 2011, 05:58 PM
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If you're looking for a replacement vortech idler, summit racing is where I got mine cheaper than vortech. You just wanna look at the diagram for it's p/n in the vortech manual to get the right one. Mine was making a horrible noise and the bearing actually wobbled back and forth n side to side.

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post #18 of 24 Old September 20th, 2011, 08:29 PM Thread Starter
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Quote:
Originally Posted by stal94gt View Post
cutting the stop has always allowed me to run about a 1/2 inch smaller belt without issues. im not sure if it was just my car but the 108 belt was so damn small. i could not get it on a 3.33 pulley without the stop cut. once i got to the 3.0 pulley it was still sitting slightly past the stop once i had cut it. our tensoner relaxes as you rev the motor so the tighter your belt is the less chance for belt slip under load.
Cool good info...thanks bro! I dont even know what the stop looks like on the tensioner. Im curious where mine is sitting now. A 108" was tight on my 3.33 setup. For the 2.87 I had a hard time getting a 107.5" on. But this 108" it goes on pretty good, and theres about 1/2" of slack up and down on the belt.

I may try cutting the stop next time to see how that does.

As far as the AC pulley, the belt does screech at WOT or even like 3/4 throttle when the AC is on, and the car isnt fulley warmed up. I think I might change that pulley. Any recomendations on brand? Just OEM?

Off topic, but how do you run a IW 15% OD crank pulley? The waterpump pulley and harmonic balancer are like a 1/2" if that away from eachother. And the oil drain is close too.


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post #19 of 24 Old September 20th, 2011, 09:33 PM
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Quote:
Originally Posted by Shaun03GT View Post
Cool good info...thanks bro! I dont even know what the stop looks like on the tensioner. Im curious where mine is sitting now. A 108" was tight on my 3.33 setup. For the 2.87 I had a hard time getting a 107.5" on. But this 108" it goes on pretty good, and theres about 1/2" of slack up and down on the belt.

I may try cutting the stop next time to see how that does.

As far as the AC pulley, the belt does screech at WOT or even like 3/4 throttle when the AC is on, and the car isnt fulley warmed up. I think I might change that pulley. Any recomendations on brand? Just OEM?

Off topic, but how do you run a IW 15% OD crank pulley? The waterpump pulley and harmonic balancer are like a 1/2" if that away from eachother. And the oil drain is close too.
To run any thing larger than a 7.5 inch crank many have had to trim the lip on the back id the romeo water pumps. Also you will have to grind down the bump on the timing cover where the timing marks stick out and the crank shaft position sensor goes in.


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post #20 of 24 Old September 20th, 2011, 09:36 PM Thread Starter
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Doesnt seem bad. I think Im going to replace my AC pulley. I have a feeling thats what causes it to sometimes squeal only on startup, since it squeals when the AC is on and I go more then 1/2 throttle.


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