Unibelt destroyed

[pns0ccc]

While increasing speed the unibelt came apart. Fortunately I made it home with no problems. This is the second belt in the last 9 months to do this. Any suggestions?

 

[JT ZR-Won]

Are you saying the actual belt under the hood snapped? Maybe check the tensioner pulley to make sure there's tension.

Jay

 

[Robertwav1]

Is it the correct belt? I have a 93 and it takes a double sided serpentine belt. Part stores have tried to sell me a one sided belt. The only place I can get the correct belt is Chevy...even with that I have to take the old one with me. Since new only the 2nd belt. Hope this helps!

 

[Ken]

It may not be the cause of the problem you are experiencing, but one of my fellow club members was experiencing tossed belts on his early C4 ('84-'85 I think) and was unable to figure it out until they found a cracked A/C bracket. The bracket only had a hairline crack, and you could just barely see it if you really looked hard, but it would flex at speed and the gap would grow wider causing the pulley to lose the belt.

Just a thought.

 

[pns0ccc]

Since the belt disentegrated I'm leaning toward reply #2.



1. I believe the tensenior provides adequate pressure to maintain correct tension but I have access to a belt tension gauge and will test for correct deflection.
2. The last two belts I replaced were ribbed only on one side. This may be part of my problem and I'm going to purchase the OEM belt from my local Chevy dealer.
3. Ken, thanks for the information on the A/C bracket. The Compressor was replaced the last time the belt failed. It appears the rate of speed and RPM was to much and the system failed. I cannot see any cracks as of yet but will have the bracket NDT by some friends.
Thanks to all of you!

 

[c4cruiser]

The belt tensioner arm has a mark on it that lines up with other marks on the tensioner housing. The marks are use to guage the amount of spring tension left. The spring will lose tension after some point resulting in a loose belt. When the mark on the arm is at the mark on the housing that is at the opposite end of the arm's forward movement (direction that exerts pressure on the belt) it's probably time to replace the tensioner.

There is also an idler pulley below the A/C compressor and P/S pump. That bearing may have worn out. You should have a belt with ribs on one side only. Double ribbed belts were only used on 92 and 93 LT1's.

The A/C bracket (which is big and a real PITA to remove!) is made of aluminum so there is also a possibility that one of the arms that hold the alternator or A/C compressor may be cracked.

 

[Vettelt193]

The two sided belt earlier mentioned is only on 1992-early 1993 cars. The switch to the one sided ribbed belt was a mid year change in 1993, so your 1996 should use a one sided ribbed belt.

 

[pns0ccc]

I appreciate the information about the belts with ribs on one side. The local dealer reported the belt for my car is ribbed on both sides yet when I asked the local NAPA dealer his are ribbed on 1 side.
I've cleaned the brackets with Electra-Clean and will apply the dye with a black light to check for cracks first. Any suggestions are appreciated. After working on everything from computers to Exciters larger than your garage the corvette is always a challenge that keeps my interest.

 

[WhalePirot]

With all that mechanical/electrical know-how, you likely know to check the belt driven accessories for freedom of rotation. A '96 probably has enough miles to be vulnerable to component failures, whether water pump, alternator, idler or A/C compressor.

 

[pns0ccc]

C4 Cruiser was correct about the belt, it is ribbed on one side for the 96. Chevy dealer delivered new belt yesterday and I installed last night in 5 minutes. Tensioner is working properly since belt deflection is minimal (1/4") and stretching the belt over/around the pulleys was quite an effort.
No cracks or defects found on the brackets for A/C or Alternator (inspected in place), but this inspection did turn up an external cut on the radiator hose from the belt failure.
WhalePirot, know-how is helpful but nothing replaces the actual experiences of people like yourself. Your suggestion prompted me to inspect the idler pulley again. Visually it appears to be working but today I will remove it and inspect closely. By the way the car has 65k miles.

 

[billd]

The are only a couple of reasons for one of these belts to come apart like you are describing.

1) (most likely) One pulley is just a little misaligned any of the accesories could provide this opportunity for failure. The most likely cuplrit would be the tensioner pulley and its bracket since these two parts are the most dynamic of all of the pulleys. You also might want to check the status of your smog pump since these are ususally the most neglected accessory on the front oof the engine.

2) too much tension (this is very unlikely unless you have changed pulley diameters)

3) defective belt (extremely unlikely since two have broken)

4) worn out pulleys is any of the pulleys are worn out they could cause the belt to track to one side or the other. This will eventually cause to belt to ride up onto the edge of the pulley thus causing failure.

 

[pns0ccc]

The belt appears to have split before breakage occurred as if the ribs separated. I've sent the old belt to the corporate lab for failure analysis. The first belt lasted 63,000 miles and the second lasted 2k. Also the second belt was an off brand I purchased from a local auto parts store and not an OEM from the dealer.
The misaligned idea is quite possible. Due to the location of the pulleys a straight edge is possible but I do have access to a laser alignment tool that can shoot an edge across the faces and give a correct deflection. I'm with you on this one since the pulleys are original but the A/C compressor is new and may have been installed without checking for alignment.
I've road tested the new belt with no noticeable problems. Results will follow
.

 

[WhalePirot]

Thank you

pns---
It feels real good to help and thanks so much for the compliment. At times I feel like the odd-guy, as I decry some of the tweaks so many here speak of. Ken has urged me to continue to share the lessons I have learned through trying things and listening to those in the trade, with truthful insight and experience, based upon years of success with our marque. I have had a number of Corvettes since 1972 and have worked on nearly all of them, in serious fashion. It'd like to think that some know-how has rubbed off and I intend to speak the truth, not regurgitate some marketing hype.

Now, it seems the A/C may be the culprit as things seemed to be okay before it was changed. Hopefully you got a quality replacement and it was installed and aligned properly.

Thank you for your follow-ups with this issue. I envy your access to some of those tools.

I truly hope your problem is resolved so you can enjoy the car, unfettered.

 

[RonV87]

I have a 1990 Trooper with a GM V6 engine and it has in the last year destroyed 3 belts well before their time. They separated at the ribs and were thrown off. For two of these I was actually able to put back on the belts minus 2 ribs and limp home. After much troubleshooting and replacement of the tensioner pully it turned out to the tensioner (also a GM product) itself. It was "catching" somehow inside so it was intermittently putting additional tension (and stress) on the belt. A tensioner isn't ok just because it causes the right amount of belt deflection. Just a thought.

 

[billd]

I still think it was probably the tensioner. The reason I think this is because if the tesnioner wheel is not just right it will exert a point load on one side of the belt and will cause it to pull to one side or the other. You can try an experiment with the wheel by purchasing a new one at a parts house. they only cost about $10.00 and who knows it might be your solution.