3 Alternator straps in 2 weeks!!

[Pastelweiß]

The mechanic who looks after both my bug and bus is a little stumped so thought I'd see if any of you guys had suffered from the same thing.

Couple of weeks ago took the bus down to T2D to get lowered (super chaps by the way) and en route the alternator strap decided to snap. T2D diagnosed a buggered alternator, and popped a new strap on there to help get me home. Which I did with the aid of the RAC in the end after this one also snapped.

Back in Leeds I had a new alternator fitted complete with strap number three, and everything was fine until we were coming back from Salisbury on Sunday, when it decided to snap again half way up the M1. Not only did that strap go, but also the one that holds the coil to the fan housing also snapped (something that John at Beetle People in Leeds hasn't seen happen in 40 years of working on them apparently!).

Clearly there has to be some crazy level of vibration going on to keep snapping these things, but everything is bolted down nice and secure.

Anyone got any ideas? One of these days I'd quite like the bus to make it home under it's own steam rather than on the back of a recovery truck!!

Cheers,
Jonny

 

[the_troupster]

Very odd. Get your hand around the back of the fan housing and check all the vanes are in place on the fan???

Jim

 

[67panel]

sounds like out of balance fan ,seen them crack from central hole and not allways easy to see even when off.

 

[Pastelweiß]

Thanks guys - much appreciated. Will give the fan a good checking over!

 

[sjc]

I had a strap that came loose that was caused by a cracked fan couldn't tell till it was off the bus though as it was around the centre hole.

 

[krusty]

My strap snapped once, and funny enough it was on my way back from t2d. :lol:
It was because the fan was not spinning with the alternator, because the rectangular cut out that makes the fan spin with the alternator had rounded out, I would say its worth checking that the fan spins properly when you turn the alternator wheel.

 

[Pastelweiß]

Thanks again for all the suggestions guys - turns out it was actually the flywheel that was causing the problem!

Bit of a result too in that my mechanic is only charging me for 3 of the 7 hours of labour!!

Looking forward to having Clarence home again - if it ever stops raining we might actually head out camping again soon!!

 

[Trikky2]

Ok I'll bite - i dont understand - how did the flywheel cause the alternator strap to fail?

 

[68_early_bay]

Ok I'll bite - i dont understand - how did the flywheel cause the alternator strap to fail?

That's what I was just thinking ............

 

[Mr Brightside]

Ok I'll bite - i dont understand - how did the flywheel cause the alternator strap to fail?

Extreme vibration ?

Still don't see how that would break the strap repeatedly though

 

[Pastelweiß]

It was extreme vibration causing the strap to fail - massive difference in how it's running now!

 

[Trikky2]

Are you sure you dont mean the bottom pulley? The flywheel is the other end of the engine between the engine and the gearbox :lol:

 

[Pastelweiß]

Yep, definitely the flywheel! I know which one it is because my bug has a nasty habit of pi**ing oil out of its flywheel oil seal!!

My (limited) understanding of this problem is that the flywheel was out of balance, and what with it being a fairly weighty bit of kit this caused some pretty significant vibration. Over long journeys (Leeds to Cambridge and Leeds to Salisbury), this vibration caused the strap to eventually fail.

If it wasn't that, next time it happens he can fix the bugger for free!!

 

[sjc]

surely if it was vibrating that much everything would be fucked :shock:
its got to be a lot of vibration to cause metal fatigue that quickly and i would have thought everything else must be in pretty bad shape if its truely the cause. can't see it doing the crank a lot of good for example

 

[sparkywig]

I'd hate to think of the battering the case has had as well.
Surely if it was that out of balance you would have noticed as soon as you started the engine.

 

[Pastelweiß]

The case taking a battering does concern me - but I'm (unfortunately!) no mechanic so I guess I have to trust in his knowledge. And of course keep tapping into the huge amount of knowledge on here!!

I'll be trying to keep an eye on things as much as I can over the next few weeks, and see how we go.

 

[sjc]

so what has he done?
changed the flywheel?
it must have been running proper rough if it was that out of balance in fact i am surprised it was still attached to the crank

 

[Trikky2]

Well... dont know what to say really.. - Seems pretty weird to me.

For a flywheel to be out of balance - well thats not something that just "happens". Either its correct or not at the time of manufacture - its not something that develops.

The only cases of flywheel shake I have seen is when it was not torqued up/fitted correctly so it was out of true or coming loose, which always caused ovaling of the locating holes and damage to the locating studs on the end of the crank.

For a flywheel to be so out of balance as to cause an alternator strap to fail, the vibration would be enormous and would violently shake the whole vehicle when you rev it. Additionally the main bearing, the fywheel centre and case close to the flywheel would suffer severe damage and/or fail before long. [puzzled smily]

 

[67panel]

whs^^^^^could understand a clutch cover going out of balance but flywheel?

 

[Pastelweiß]

I'm as confused as you guys! He's replaced the flywheel, and there is a huge difference in how it's running. Problem is that I haven't been able to drive it that much in the few months I've had it to so haven't got much for a basis of comparison.