Is there a reason the belt would just pop off?

It was during a “fun run”, I spun out and it just popped off. I put it back on and everything seems to be working fine except for a vibration in the wheel when I turn at low RPM (like when pulling out of a parking spot). Someone told me it was just air in the system from turning when the built was off and that it would go away. Is that accurate? Because I drove 8 miles home and it still does it.

Thanks,
-Jason

 

When I checked under the hood after this month's autocross event, my belt was half way off the pullies. I got lucky. We were 3 hours from home at a road course for a special event. That would have really sucked to shred the belt half way home.

As far as what caused it, I'm still trying to figure that out. The only thing that I can think of is slack in the belt somehow. But the tensioner is directly after the crank pulley. So the rest of the belt would still be under tension because of the crank pully pulling it. I was thinking that the AC compressor might be between the crank and tensioner causing a drag on the belt there causing slack. But that's not the case. Maybe if the engine was spinning at 4500 RPM and suddenly was slammed down to 0 the momentum of one or more of the accessories could make some slack before the next accessory pulley. But that doesn't seem right either. Otherwise they would be throwing belts all the time on the dragstrip.

Funny thing is, in my last fun run I set out to try and drift the back end around 1/4 of a wide figure 8 and spun too. But I down shifted to 2nd half spin and kept my foot in it. So the RPM's never dove suddenly. I'm stumped.

 

Any chance that while you were spinning you didn't have the clutch in, and the engine got spun in reverse direction? I'd think that could be quite exciting, and the belt may want to get away from those pulleys fast... which could be the least of the problems I suppose.

Dave

 

That would definately do it. But I know for a fact my engine never spun backwards. As soon as it started to bog down I hit the clutch and it never stalled.

But that would definately do it.

 

I have an automatic, and the car never really bogged. Infect, I new it was going around and I stayed on the gas to bring her back around.

After a commute to school and back, my vibration problem has not gone away. I think I’m going to post in the Tech forum and see if anyone knows what could be up.

My tensor felt nice and tight when I put the belt back on so I don’t think that’s it.

BTW, I have an LT1, if it makes any difference.

 

Take the belt back off and inspect it to see if you sliced off any of the ridges. That would definately cause a vibration, I'd think. And if the belt is nearer the end than the beginning of its lifespan, it may have stripped off a little bit.

 

Anytime you run a n engine that hard at those RPM you have to worry about the belts. Guys with V-belts throw them all the time. As for what causes it the main theing is pulley alignment is out by a little. Good enough for normal driving or even hard driving but not for racing. I assume you have a 4th gen with a sepentine? most people here do. Check the obvious, GM belt tensioners suck *** so start there. Check the belt and also make sure that your accesories are all working smoothly. If that checks out then start making sure that your pulleys are aligned nice and shim if they are not.
Good Luck
CoryM

 

Just a thought...

Do you guys think the belt tensionor is not picking up the slack on the belt quick enough?

Could one maybe losen the belt tensionor slightly so it moves more freely, seems it does not move real quick, maybe grease the heck out of it?

Jsut a thought.

 

Another thought, even though this thread seems to be dead.

is maybe why it happens autoXing and not drag racing is because the power steering pump isn't pumping hard down the strip but under turns its putting more pressure on the belt.

I am kinda glad i never threw out my old bet I might piut it in my car tool kit to jsut to be safe.

 

Update:

The vibration went away on it's own after a few days.

My belt didn't look too bad, but I put a new one on anyway. I autocrosseed last weekend and the belt never pooped.

I wouldn't be surprised if I have a week tensor though. I am going to see if I can find a spec. as to how many pounds of force it is supposed to be applying.