Alt and PS belts

[Mustang]

Ok my car has just gobbled up it's second set of belts in about 8 months
Had new belts fitted about a year ago. All was fine until about 8 months ago it gobbled up the alt and ps belts, (granted It was at~8000rpm at the time). One of the tensioners seemed a bit slack, so I replaced bothe tensioners and belts, they were slipping a bit recently with the cold wet weather. So tighened them up recently. This morning (on my way to the airport) and another 8000rpm blast, it's gobbled the belts again. Thoughts please?

[Gwyn]

Shift Up

[Myfeckin FTO]

Why is the push to 8000rpm causing them to shred?
Is there an imbalance there somewhere between the pulleys and tensioners - perhaps there are bearings gone on a pully thats causing the belt to jump at high RPM.

When you say you tightened them - to what tension? You should just be able to twist the belt to a max of around 45 degrees.
What belts did you use?

Anymore damage than just belts? - count yourself lucky if not - a loose belt can take out a lot of ancilaries when it starts to flail.

[Muad_dib77]

Check the edges of the pulleys Musty..

Also - I last I put new belts on - I tightened them ALOT - but after about 3 day of driving..I though - "aaah I'd better check.." as I was checking oil levels anyways.. As I prodded the belts they definately more slack than previous.. so I tightened them again..only a few turns on the tensioner bolts - but that can make a difference between having powersteering and not having powersteering..

Since that I've had no problems..


Oh and isn't it a "great" feeling when the PS belt jumps off mid turn?? Sure got my heartrate up a bit.

[Daz]

When you say you tightened them - to what tension? You should just be able to twist the belt to a max of around 45 degrees.
What belts did you use?

Its not often i disagree with you mffto but thats too tight mate, i've worked on machines that use drivebelts of all shapes and sizes for years and years and the max tension on a belt should have a twist of 90deg, but prefareably closer to 180 deg having them too tight is almost as bad as too loose, when too tight the pick up on inbalances quicker and will wonder at the slightest ofset and in somecases snap under duress of high torque.

But in any case check this out it might help

http://moodle.student.cnwl.ac.uk/moodle ... ebelt.html

Daz...

[Myfeckin FTO]

Its not often i disagree with you mffto but thats too tight mate, i've worked on machines that use drivebelts of all shapes and sizes for years and years and the max tension on a belt should have a twist of 90deg, but prefareably closer to 180 deg having them too tight is almost as bad as too loose, when too tight the pick up on inbalances quicker and will wonder at the slightest ofset and in somecases snap under duress of high torque.

But in any case check this out it might help

http://moodle.student.cnwl.ac.uk/moodle ... ebelt.html

Daz...

Hmmm! I'm just going on what a couple of mechanics have told me. Perhaps 45degrees is not absolutely correct but appartently you should be just barely able to twist them enough to see the underside of the belt - so I guess somewhere between 45 & 90 degrees. I would have thought that if you can twist a belt 180 degrees then its too loose.

The tension range at which belts should be installed depends on the drive components, and the load and speed of the drive. - the ideal tension for a belt would be the lowest tension at which the belt will not slip at the highest load condition. Therefore what has worked on machines in your workshop may not work on a 200bhp FTO revving at 8000rpm.

I had my belts changed twice on the last FTO over 50K miles of driving and had no problems having fitted them with somewhere between 45 and 60 degree tension. I guess its also important to examine the pulleys and make sure the alignment is correct and theres no sign of wear or vibration on any pulley and ensure the tensioner is not vibrating badly while running.

[Daz]

Hmmm! I'm just going on what a couple of mechanics have told me. Perhaps 45degrees is not absolutely correct but appartently you should be just barely able to twist them enough to see the underside of the belt - so I guess somewhere between 45 & 90 degrees. I would have thought that if you can twist a belt 180 degrees then its too loose.

The tension range at which belts should be installed depends on the drive components, and the load and speed of the drive. - the ideal tension for a belt would be the lowest tension at which the belt will not slip at the highest load condition. Therefore what has worked on machines in your workshop may not work on a 200bhp FTO revving at 8000rpm.

I had my belts changed twice on the last FTO over 50K miles of driving and had no problems having fitted them with somewhere between 45 and 60 degree tension. I guess its also important to examine the pulleys and make sure the alignment is correct and theres no sign of wear or vibration on any pulley and ensure the tensioner is not vibrating badly while running.

i wouldn't go beyond 180 deg i usually settle for between 110 and 150 deg, and some of the belts i fit are fitted to machines that pull a hell of a lot more torque than any car would, think of the power required to turn a 1 foot diameter shaft with stirers on it in a silo 150-200 ft high full of either flour or sugar as you can imaging thats serious power required to do that. granted we use reinforced belts too but the principle is the same.

Daz...

[AL]

check the Air Con clutch pulley for wear or seizure of the clutch spring, also check crank pulley for wear, both might need replacing for new.

[Mustang]

check the Air Con clutch pulley for wear or seizure of the clutch spring, also check crank pulley for wear, both might need replacing for new.

Thanks AL, that's the type of input I was looking for.
I'll fit the replacement belts myself, keep the revs down, and get it looked at professionally. Thanks.
Just to clarify the original replacement belts were fitted by my mechanic, (just in case the finger of blame is being pointed squarely at me).
Yes I followed the tensioning guidelines when fitting, and only tightened them slightly, there recently.

Well arrived back at the airport yesterday, fortunately the car started.
Drove home in the rain, with no wipers or heater, one hand on the non-power assisted steering, one hand franticly wiping the windscreen, to stop it misting up. One eye on the road, one eye on the volt meter.
Made it home anyway.

[mcgon1979]

this happened me a month or two ago. after some 8000rpm driving... alternator belt and PS belt shredded. my mechanic reckoned a stone hopped up as the belt pulley is not protected from the ground.
Got a new belt, set the tensioner again and been fine ever since...

[Mustang]

this happened me a month or two ago. after some 8000rpm driving... alternator belt and PS belt shredded. my mechanic reckoned a stone hopped up as the belt pulley is not protected from the ground.
Got a new belt, set the tensioner again and been fine ever since...

Thanks for the input Mc but in my case I'd be very unlucky to have two stones hop up on two seperate occassions, both while engine speed is 8000+ rpm. A statistician would call it "statistically significant".

Well I contacted camskill and Mike reckons that more than likely it's the crank pully. http://www.camskill.co.uk/products.php?plid=m3b0s9p5797.

This is the pulley that falls apart and destroys your crank angle sensor and can if it hits the propeller plate hard enough chop right through the cambelt in the process!
The first signs are it throwing belts off and shredding them and this can also wreak havoc on the sensor.

Change it BEFORE it happens!

The first signs are it throwing belts off and shredding them.

[Myfeckin FTO]

...........

Well I contacted camskill and Mike reckons that more than likely it's the crank pully. http://www.camskill.co.uk/products.php?plid=m3b0s9p5797.

This is the pulley that falls apart and destroys your crank angle sensor and can if it hits the propeller plate hard enough chop right through the cambelt in the process!
The first signs are it throwing belts off and shredding them and this can also wreak havoc on the sensor.

Change it BEFORE it happens!

The first signs are it throwing belts off and shredding them.

...............Is there an imbalance there somewhere between the pulleys and tensioners - perhaps there are bearings gone on a pully thats causing the belt to jump at high RPM.

.................

.................. its also important to examine the pulleys and make sure the alignment is correct and theres no sign of wear or vibration on any pulley .................

What did I say on my first and subsequent posts!

[Mustang]

Gold star for myfeckinfto. . And I do appreciate everyones input. However that much is obvious enough, what I was hoping for, was for someone to say exactly what was wrong, as they had seen the fault before. e.g."Yea that would be your triple rotor inverse flux capacitor. Same happened me '95 GPX, common fault, cost me a bleddin' fortune" etc.

[Myfeckin FTO]

Gold star for myfeckinfto. . And I do appreciate everyones input. However that much is obvious enough, what I was hoping for, was for someone to say exactly what was wrong, as they had seen the fault before. e.g."Yea that would be your triple rotor inverse flux capacitor. Same happened me '95 GPX, common fault, cost me a bleddin' fortune" etc.

Well - I can say with some conviction that the problem doesn't lie with your "triple rotor inverse flux capacitor" - these are generally very reliable units and last nearly as well as the G Force meter.

[Sebastian]

did a check on the engine last day after 2 weekends of high revs, long distances and crazy driving .

PS belt is shreddered , only holding on a few bits.
got the belt from camskill ( 1.5 days delivery .. well impressed) so i'm thinking to give it a go in change it myself during the weekend.
is it dificult?

so it's a common problem belts dont last long on a hard driving ?

[Wildhound]

PS/Aircon belt is a very easy swap in itself, there's just not a whole lot of space. It might be easier to jack up the car and do it from underneath. That said I was taking off the PS and Aircon pumps at the time so the belt alone might come out easy enough from the top.

Either way you're looking at 20 mins tops.

[Muad_dib77]

Yeah 20-30min job - it's tight for space under the car - I parked two wheels on a kerb last rather than jacking it up.
I've actually replaced the belts in the company car park - doesn't take long at all once you locate the tensioners.