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MG MGF Technical - Alternator belt tensioner weakness

Alternator belt needed tightening (squealing on startup), levered the alternator tight & bolted up the adjuster. A few days later the squeal returned and got quickly worse, until finally silence accompanied by a red battery light on the dashboard. Anxious remainder of 120 mile journey home with AA card handy...

Inspection showed pretty quickly that the tensioner bracket had sheared off near the block end of the part with the central cut-out, leaving the belt flapping loosely and some very sharp edges... OK the plastic cover on the timing belt ought to prevent expensive entanglement but it seems these brackets aren't as strong as they ought to be. A new one is only £4.57, I'd recommend anyone finding they need to tighten the belt to consider this possible cause.

Has anyone any suggestions on how to reinstate/replicate the central stud fitting on the insulation panel? Drill in alongside it & machine screw? It sheared off long before my ownership, used best ingenuity but there are some situations not even gaffer tape can deal with ;o)
Mike Hankin

You may be able to drill the remains of the bolt and use a stud extractor. I drilled out the broken bolt and tapped the hole. Good pillar drill and careful clamping is required or just take it to your local machine shop.
Ken Waring

It could well have been the levering that done it. The brackets have a neat tensioning screw arangement which does away with levering.

I'm not sure you should be blaming the bracket - I've never heard of one failing before. Case of RTM?
Will Munns

So that's what the hole at the end of the bracket is for... thanks Will. Seems the screw wasn't re-fitted previously :o( OK maybe I'll accept I contributed to the demise of the bracket with the technique used.
Mike Hankin

Mike
When you wrote 'sheared off' I assumed you meant the adjuster bolt had sheared inside the alternator aluminium end casting not that the bolt was missing.
Ken Waring

I think the tensioner screw will resist in both directions - so it could have been the PO that actually caused the failure - the slackening was a symptom of the bracket failing.

"the central stud fitting on the insulation panel"

I can't quite work out what bit you're talking about. If you have lost the thread into the block then I have heard "lumniweld" (available from frost) is the solution to your problem.
Will Munns

>replicate the central stud fitting on the insulation panel? Drill in alongside it & machine screw?

I think this is regarding the well know _always breaking_ upper RH screw for the alternator cover in the wheel house.

Drill new thread, a bigger one of course. Or drill a 6 to 8mm hole and push in a plastic rivet.

Dieter

Thanks Dieter, hadn't thought of a plastic rivet - good idea. I'm still puzzled as to how the bracket got stressed enough to snap, but I'll assume it was a one-off. And I'll set the new belt tension up without any old-fashioned levering ;o)

I'll try to give better descriptions in future, sorry if I confused anyone!
Mike Hankin

:) No worries.


Dieter

This thread was discussed on 21/07/2005

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