Alternator Decoupler Pulley

[Eggman]

Not one time in 30 years including everyone I knew in the industry did a belt spontaneously jump a groove.

This must be a first. Proof is in the photo - that is, presuming the story is not a fabrication.

[deleted user]

The only thing the photo proves is the belt was one groove off on the pully when the photo was taken. I'll take 30 years experience over one opinion backed up by nothing.

regards
mech

[Eggman]

The only thing the photo proves is the belt was one groove off on the pully when the photo was taken. I'll take 30 years experience over one opinion backed up by nothing.

Not sure what you mean by this.

The story says the noise started upon downshift. If the engine was previously running with no abnormal sounds before the downshift, then began making abnormal sounds after the downshift, it must have 'jumped' at that point. The driver pulled over, inspected the engine to find the belt in tatters, going as far as cutting off the loose material. If the belt was off one groove before the downshift, I would expect the noise would have been present then too.

[Mitz]

The only thing the photo proves is the belt was one groove off on the pully when the photo was taken. I'll take 30 years experience over one opinion backed up by nothing.

regards
mech

Not sure what you mean by this.

The story says the noise started upon downshift. If the engine was previously running with no abnormal sounds before the downshift, then began making abnormal sounds after the downshift, it must have 'jumped' at that point. The driver pulled over, inspected the engine to find the belt in tatters, going as far as cutting off the loose material. If the belt was off one groove before the downshift, I would expect the noise would have been present then too.

I agree with old mechanic ..

I don't believe the belt "jumped off" out of its groove. It must be already off its groove (nearer to the compressor housing) even before the engine was run. The rubber won't just tear down right away. It will take a certain time .. it just happened coincidental with the gear shifting.

The guy had his last PMS (10K) last December 2015 and experienced this on 14-Feb.-2016.

[cyclopathic]

Not one time in 30 years including everyone I knew in the industry did a belt spontaneously jump a groove.

regards
mech

That if it was tensioned properly to begin with. But if it weren't it would have been squealing like a pig long time ago. Unless it was tensioned but not tightened and worked itself loose from vibration.

Question to owner would be if belt was slipping and squealing prior to incident.

Also improper insulation usually happens at installing, why would they need to take belt off during simple maintenance? Was it installed improperly from the factory?

[Eggman]

Also improper insulation usually happens at installing, why would they need to take belt off during simple maintenance? Was it installed improperly from the factory?

I thought that the mechanic performing 10k service might have checked the belt tension, perhaps mis-reading the tension. I don't know - do mechanics use a device to check belt tension, or just go by feel? I'm sure professional mechanics always use the right tools for the job...

[cyclopathic]

^^^ The ones I know an trust do the regular half turn twist.

It is possible that some complete n00b started in wrong direction by loosing belt to the point it jumped and then tighten it?

Also haven't look at belt diagram are there any bearing pulleys? If it's gone bad it could shred belt.

[mitsumi]

since this is regarding the belt i just want to ask. i was cleaning my engine bay then i saw this.


is it a sign that i should change it? ODO is almost at 11km

[inuvik]

is it a sign that i should change it? ODO is almost at 11km

It's very easy to over tighten the belt on the Mirage. I'd continue to monitor it. You want the belt just tight enough that it never slips (squeals). Over tightening will result in premature belt failure and puts excessive stress on your alternator and air conditioner which can dramatically shorten their lifespan.

[mitsumi]

It's very easy to over tighten the belt on the Mirage. I'd continue to monitor it. You want the belt just tight enough that it never slips (squeals). Over tightening will result in premature belt failure and puts excessive stress on your alternator and air conditioner which can dramatically shorten their lifespan.

but i havent done anything yet with the belt. is it something i should be worried about or just check it once in a while/;