My 57,000 mile 2004 Sport Tdi 130 has started to make bearing failure noises at idle. It manifests itself as a rumbling noise. I first noticed it about a month / 1,500 miles ago (normally do about 10,000 pa but just back from long trip) and now my wife has commented, so I guess its getting worse. With an engine stethascope it is not clear whether the noise is coming from the drive belt idler pulley (the plastic one) or the viscous fan one. Neither feels loose when levered with a bar. Local garage advice (I live in South West France) is to leave the noise insulation cover off the engine and closely monitor both components until one is clearly the culprit.
The cambelt and kit of parts were replaced last year, but the garage didn't replace anything to do with the aux drive belt (no reason to I guess and I didn't ask them to).
So, what experience does anyone have with either of these items? Obviously replacement is expensive as the front has to come off the car (again!!). Unless I can clearly identify which is failing, my inclination is to replace both whilst the front is off. Any comments? (I can no longer do jobs like this myself due to arthritis).
Thanks in advance for any help.
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Take a look to see if the belt tensioner is not bouncing at idle where you appear to report the noise. If it is and a sligh increase stopd the noise and bounce then I suspect the Spragg clutch has seized in the alternator pulley. Quite common. Regards Peter
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Good advice above - the alternator one way drive pulley is a favourite failure point, although your car is a bit young for this (80k miles to failure is about average). The drive will oscillate at idle when this seizes and other drive components will be quickly damaged if it is not replaced.
Of the two other wheels you mention, the tensioner is the more likely to fail as it's a plastic wheel with a rather insubstantial bearing within it. The fan bearing is a much more solid affair. You could get your garage to release the aux drive belt and slip it off the pulleys (this can be done in situ if you leave it hanging around the crank pulley), then you can assess these bearings individually. The fan assembly is held in by a single bolt (internal 8AF hex head) which is accessible through two holes in line at the back of the bracket. Releasing this bolt (you need a means of holding the fan pulley drum - there are 2 holes in it for a special VAG tool) allows the entire viscous fan assembly including bearing to be slid forwards - but you would probably need to move the front panel to get it right out.
Another way of holding the fan pulley whilst releasing the retaining bolt (RH thread) is to wind a double sided strip of glass paper between the belt and the drum, then use a 19AF OE spanner to increase the belt tension on the hex provided on the tensioner and use the belt itself as a strap wrench with the vehicle in gear. This is as good as the VAG tool.
659.
Edited by 659FBE on 27/01/2010 at 14:09
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What a great, detailed response. Many thanks 659
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