VW Golf GT TDi 140 - Tensioner stud shears in VW Golf - any recompense?

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Fri 24 Jan 2014 12:35
VW Golf GT TDi 140 - Tensioner stud shears in VW Golf - any recompense? - AZL

Got "persuaded" to have cambelt and tensioner changed at 80,000mile service of 07 reg Golf at VW garage. Had been done at 57,000 miles 20 months earlier at a different VW garage.

14 months and 20,000 miles later, car breaks down; rescue service suggest fault is cambelt component.

VW garage who did most recent change say the tensioner stud has sheared off, likely caused by driving through floods, which I didn't. I organised to get Dekra engineer out, VW revised this preliminary diagnosis of damage by water.

Dekra confirm tensioner stud sheared off. Hadn't been replaced by garage when cambelt and tensioner had.

VW have introduced a replacement stud into their kits as of August 2013. Garage say not their fault. £70 for tow truck, £195 for Dekra, ~£500 to check engine, need new cylinder head, so further cost just over £3k in car worth max £4,500.

Any point taking this further with VW given previous posts on this on HJ? Got 3 other VWs....

Thanks a lot.

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Fri 24 Jan 2014 14:36
VW Golf GT TDi 140 - Tensioner stud shears in VW Golf - any recompense? - 659FBE

I have contributed to this topic on previous threads (sorry) and there is clearly a design problem here.

My view is that the VAG recommended tightening specification for the tensioner retaining nut (20Nm + 45 deg) is excessive and will stretch the stud beyond its elastic limit. Experience suggests that if the stud is not over tensioned at the first belt change, it will generally survive, but if it is tightened to VAG's spec on the first belt change, it will sometimes let go shortly after the second.

It's interesting to hear that VAG now include the stud in their kit. I buy Continental kits which include the proper Litens tensioner and until recently, the kit has always included a stud. The last two I have fitted were supplied without a stud. Clearly some muddled thinking in the Fatherland.

My view based on experience is that the stud is fit for re-use as long as it is tightened to 20Nm + 20 deg, and no more. This is entirely sufficient to provide enough locking tension within the stud. Interestingly, the advice from Litens is to tighten to 23 Nm only. I have checked, and this value corresponds almost exactly to 20Nm + 20 deg.

This is a really nasty failure - the tensioner is secured by the "Jesus nut" (helicopter gearbox terminology) of the engine. You are very unlikely to get anywhere with VAG given their record. There are other tightening specifications on these engines which do not align with my engineering experience. The 4 harmonic damper bolts are specified to 10 Nm + 90 deg. As they are set bolts running in threads up to the head, this torque causes them to shear off when removed as they are of 8.8 material specification.

To summarise with the tensioner - replace the stud if it has been tightened more than once to the VAG spec, then consider my suggestion of 20Nm + 20deg. PSA specify 20Nm only for the same nut on the same size of stud (M8) in their diesels. I've not heard of any coming loose.

659.

Edited by 659FBE on 24/01/2014 at 14:38

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Fri 24 Jan 2014 14:52
VW Golf GT TDi 140 - Tensioner stud shears in VW Golf - any recompense? - AZL

Thanks 659. Have read previous threads and found it all very helpful - in a "I'm not the only one" way. Yeah, VAG not likely to be too interested. Although I see in the States there was a class action law suit. Go the little guy!

AZL.

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