Anyone ever have this happen?

MadMikeyL

SCCoA Member
I'm driving into work today, going down the highway about 75-80mph, and all of a sudden the car loses power and starts slowing down. My first thought is the engine stalled, but no idiot lights on the dash, and the AFR gauge is bouncing between 14 and 15. Push the clutch in and hit the gas, and it revs freely, and settles to an idle right around 1000rpms while coasting in neutral. Put it back in gear, and I can maintain about 60mph tops at part throttle, but if I try to go over that, it just falls on its face. Aha! I know what that means, I must have snapped a supercharger belt. No big deal, I have zip-ties in the trunk to tie the bypass open for the drive home, and then I'll just buy another belt. Meanwhile I'm thinking this is weird because the belts are only about 6 months old. Well I get to work, pop the hood, and here is what I see.



Both belts look to be in good shape, no glazing or cracking, but both are popped off their tensioners! Anyway, anyone ever have that happen, and if so, what is the solution so it doesn't happen again? FYI, the car is running a 10% SC pulley and a 5% JS pulley, MP springs in both tensioners, and both tensioners were clocked to keep them within their normal range. The car has been my daily driver the last 6 months and I have been beating on it regularly with no signs of belt slip or any problems until now.
 
Anyone running 10% pulley on the SC and thinks its not slipping is a king of wishful thinking.

Yes, this has happened to many before. Easiest fix is to put a 5% or stock SC pulley on.
 
I had trouble throwing my belts off. I checked everything. Turned out that the tensioners were wore out. they were deflecting as the moved. New tensioners and problem was fixed.
 
Anyone running 10% pulley on the SC and thinks its not slipping is a king of wishful thinking.

Yes, this has happened to many before. Easiest fix is to put a 5% or stock SC pulley on.

Trust me, it doesn't slip. It pulls 18psi up to 6000rpms. It took clocking the tensioners AND the MP springs to get it to not slip, but it doesn't slip.

I had trouble throwing my belts off. I checked everything. Turned out that the tensioners were wore out. they were deflecting as the moved. New tensioners and problem was fixed.

When you say they were worn out, was it the springs worn out, or is there something else that wears? I rebuilt this motor and put it in about 6 months ago, and I installed the new MP springs at the same time. I think I have another set of tensioners somewhere that I could swap the springs into if you think that would solve the problem.
 
Years ago when I actually had a M90 I made a bracket to install an idler pulley to give a lot more wrap to the SC pulley. I beleive one of the local guys, Sam down in Lincoln NE still has his on. Worked great as it gave a bigger contact patch on the small pulley.

Ken
 
Years ago when I actually had a M90 I made a bracket to install an idler pulley to give a lot more wrap to the SC pulley. I beleive one of the local guys, Sam down in Lincoln NE still has his on. Worked great as it gave a bigger contact patch on the small pulley.

Ken

Interesting idea. Have any pics? I assume it would attach to some of the water pump bolts to pull the belt in on the other side of the blower? Would you be willing/able to make another one?
 
Interesting idea. Have any pics? I assume it would attach to some of the water pump bolts to pull the belt in on the other side of the blower? Would you be willing/able to make another one?

Actuall I still have mine sitting at home in my garage. It was very simple. No one seemed interested in it at the time. Might have to make a pattern for it should I sell it. I will see if I can get a picture of it

Ken
 
Anyone running 10% pulley on the SC and thinks its not slipping is a king of wishful thinking.

Yes, this has happened to many before. Easiest fix is to put a 5% or stock SC pulley on.

I have been running a 10% pulley for years and I never had a belt jump off!

Very odd. Did you check the blower to be sure it's not locked up? (Unlikely, but worth looking at.)
 
I had trouble throwing my belts off. I checked everything. Turned out that the tensioners were wore out. they were deflecting as the moved. New tensioners and problem was fixed.

I had the same problem with the accessory belt tensioner several years ago and solved it by installing a new one. On mine the arm/pulley wasn't staying parallel to the belt because tensioner had too much slop/wear and was causing the belt to walk off the alternator pulley. On this car either of the blower belt tensioners could be causing the same problem. One belt coming off probably got tangled up with the remaining belt and knocked it off.

Another possibility is bad balancer and wobbling crank pulley.

David
 
I have been running a 10% pulley for years and I never had a belt jump off!

Very odd. Did you check the blower to be sure it's not locked up? (Unlikely, but worth looking at.)

I can't right now because the way the belt is half on and half off, and I don't have any tools with me. I will check that when I get home. The blower is a MP2 case, and I installed a low-mileage set of 94/95 coated rotors and fresh fluid when it was installed 6 months ago, so hopefully it is OK. What is really weird about it is how it failed while cruising on the highway, not even under any boost.
 
I can't right now because the way the belt is half on and half off, and I don't have any tools with me. I will check that when I get home. The blower is a MP2 case, and I installed a low-mileage set of 94/95 coated rotors and fresh fluid when it was installed 6 months ago, so hopefully it is OK. What is really weird about it is how it failed while cruising on the highway, not even under any boost.

Are you using a stock balancer ?

David
 
Problem found!








That is the jackshaft belt and tensioner. The split was down by the crank pulley, so I didn't see it this morning when I first looked. I'm pretty sure the belt split as a result of tensioner bearing seizing up, and not the other way around. What is weird though is that it didn't make a single squeak or hum or grinding noise or anything. Anyway, I started looking around because I know I had another pair of tensioners with the steel idlers. I wasn't able to find them, but I did find another plastic idler with a good bearing.



That is the new one installed on the tensioner with th old one on top for comparison. The new one looks to be slightly larger, but it doesn't hit on anything, so I guess that's a good thing. Everything else spins freely, and the SC belt is OK, so I'll order up a new jackshaft belt and be back on the road, and once the weather gets warmer, I'll have to look for those other tensioners with the steel idlers.
 
When you say they were worn out, was it the springs worn out, or is there something else that wears? I rebuilt this motor and put it in about 6 months ago, and I installed the new MP springs at the same time. I think I have another set of tensioners somewhere that I could swap the springs into if you think that would solve the problem.

to follow up, wore out means that the two piece tensioner has sufficient clearance worn inside that when the arm moves it can deflect enough to cause the pulley to push on the belt only on one side causing it to walk off the pulleys.

That failure is pretty cool. When I had a pulley seize up it was the top one and that went flying out from under the car and the belt flew around and knocked all the belts off.
 
Back
Top