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A too slack a belt produces a belt rattling sound but often only at very specific engine speed.

A belt set too tightly produces a slight whine or hum from the belt.

I'm struggling to explain the noise only when cold before. A faulty tensioner making a sound only when cold I think must have had an issue with the tensioning spring somehow. As the tensioner pulley will be metal, I cannot see how an issue with that or the bearing could be at fault or how it could be poor fitting (misalignment).

A really good garage or dealership would still be able to find out exactly what the fault was and be happy to tell you.
 

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Take the aux belt off and briefly run the car. Does the sound go? If so I'd guess it's a pulley or the tensioner. If the sound persists then look at the earlier suggestions in this thread. Mine was the clutch pulley on the alternator. It turned smoothly by hand but is only supposed to turn in one direction. I'm not sure of the physics behind this but although the bearings seemed good the ability to spin in both directions caused a tapping.

Don't be too hard on your garage because a diagnosis if difficult and just swapping all the parts is expensive.
 

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Discussion Starter #24
yes, I know and no, I won't. the lady in reception is too competent, is not her fault for sure, and I understand that in the end they might have not failed with me either. but it's frustrating when you choose the brand dealer to do a major job by the book (all belts, cam and aux, all tensioners and pulleys, engine oil and filter, coolant), pay big money, specially when I'm not swimming on that, and the car returns with issues...
 

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I now also have a new ticking noise.
The cambelt was done recently, to a poor standard in Royston, all the plug wells were left with water in them. The car was then SORNed as it was a MOT failure due to rusty sills. I've disconnected the battery, and been starting it up every month or so and letting it warm up followed by a bit of movement on the driveway to ensure the brakes aren't locked up. I will fix the sills at some point. Then, one time it started making this noise after it warmed up. Yes it does have oil in it. Sounds like excessive tappet clearances to my untrained ear. The car 55k on it, and with this new noise I am considering scrapping it, which is a shame as the gearbox is great, and it drives really nicely.
 

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I changed the oil and filter today, and the noise is still present. It comes in after about 30 seconds of idling, and sounds like it could be a bad tappet follower, but certainly something in the upper cylinder head. I have some time to fix this car, so I also replaced the front brake flexis. Anyone got any idea what it could be?
 
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