tensioner arm bolt shearing off

[Dark_phiba]

Hey all, first time post, only recently started having issues with my A4

couple of months ago, I had my serpentine belt tensioner arm replaced, as the bolt holding it in place had sheared off, now two and a half months later, it has happened again, new part, same issue, this time, I have the tensioner arm out, and as you can see from the pic, what appears to be a cut in the plastic.  I'm guessing this is what caused the first, I just couldn't get to it to see.

 

anyone seen this before, have an idea what could be causing the damage, I have inspected the belt, seems to be no wear on it at all, no damage not even fraying anywhere?

 

I have it booked in for Monday, but would appreciate any thoughts

[Magnet]

Hello Scott,

To other forum contributors:- Am I right in thinking someone else asked about this type of issue some time ago? 

If so, I think I asked for details of where the fracture occurred ( but we didn't get an answer?). Could you let us know Scott, and ideally post a photo of the point of shear. My guess at it would be at what is call the run out of the thread I.e where the thread ends. 

Another point of interest would be the actual supply source of this part. VAG main dealer, or aftermarket? 

Kind regards,

Gareth.

[Dark_phiba]

Sorry, been a manic weekend, I can't get a shot of the engine placement, though this is a shot of the shear point in the tensioner.

unfortunatly I don't know the source of the parts, I can ask the guy tomorrow

Appreciate the reply

[Trevor]

Not sure, but I wonder if that is the correct bolt for the unit as I would have expected to see a shoulder on the bolt and not threaded all the way up...which could lead to it being overtightened.

[Magnet]

Thanks Scott,

Well Trevor - great minds think alike. Although in my case it could be idiots always agree!

Seriously, this looks more like a B&Q ordinary mild steel rough-as-a-badger's-backside threaded screw rather than a high tensile set bolt. Probably simply sheared at some stress raiser point along the thread where these threads are rough. 

Surely, surely, this is not a VAG sourced part ( please tell me it's not Scott), but looks suspiciously like it may have been made very far east of the English channel and found its way to the local motor factors or an eBay listing. 

Really interested in this, since I'm sure someone else has had a similar experience. 

Kind regards,

Gareth. 

[Dark_phiba]

Thanks for the replies guys, I did some looking around, it may very well be an incorrect bolt, it looks like I'll be taking the day off work tomorrow to go in and chat the the garage that carried out the repairs.

 

i don't know where they source their parts from, I know I stopped using euro car parts a long time ago due to the "quality" of their merchandise.  I'll post an update when new information becomes available

 

again, many thanks

[Magnet]

Hello Scott,

Many thanks for coming back on this, and although you are yet unsure where they sourced this part, I think it's fair to say it is unlikely to be ex VAG dealer, and more likely to be their local motor factors.

Europarts? Any other aftermarket parts supllers? I think it's fair to say some aftermarket parts from any factor can be substandard , but most will usually be cheaper than main dealer full price parts. Critical application parts such as this should not - in my opinion, anyway-  be bought on price, but on understood quality. 

Very often, if you shop around main dealers then you are likely to be able to buy OE parts at discount, (I can recommend one - but I'm sure there are more ) and very often not that much more than what you might pay for the ones the motor factors throw at you from foreign parts. 

Buy once and wisely is good practice certanly if it's DIY, and even where you ad paying labour charges for fitting them

Kind regards,

Gareth.

 

[Trevor]

Bought this tensioner for an Alfa Romeo yesterday and look at the bolt, lol....you couldn't make it up !

Going to substitute it for the original one and nut-lock it into place to avoid loosening off tension but not convinced it looks a quality bolt although the tensioner is okay as have used these loads in the past and never had any problems.

I think also, that if overtighten given that it has a lot of thread area to stretch that this could lead to failure...hence the nut-lock to avoid having to graunch it down.

[Magnet]

Well Trevor, I am amazed, particularly since this is an INA bearing, and they are supposed to be/were very reputable and I believe supply OE to the motor manufacturers. 

A couple of questions:

Did you buy it as part of a kit ( e.g. I know Gates were using INA tensioners for example)? 

Have you checked with INA Technical on this, to confirm it is indeed a genuine INA product? 

Kind regards,

Gareth.

p.s. I still maintain that these at least look similar to a conventional mild steel bolt rather than a high tension one. What are the markings on the head Trev? Our freinds very much far east of the channel are great at replicating what things should look like! 

[Trevor]

I totally share your concerns Gareth, definitely genuine INA, made in Slovakia but not sure about the origins of the bolt.

Although it certainly looks better than Scott's bolt, I still wouldn't say it is a tensile quality bolt and therefore will probably use the original one.