Broken idler stud

Discussion in 'VW Mk4 Jetta, Golf, New Beetle, Passat TDI forum' started by Fingers, Aug 18, 2011.

  1. Fingers

    Fingers Member

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    I was replacing my timing belt today and when I was torquing the idler nut my torque wrench didn't 'break'. As a result I overtorqued the nut to the point I broke the stud. :eek

    There was some colorful language but in the end I had to remove the freshly installed belt and call my dealer to order a new stud. Of course I don't live anywhere near the dealer and they can't get the part until tomorrow so my work came to an end.

    Has anyone had to replace one of these? I couldn't find any details in the manual but I'm assuming it's a reverse threaded pin into the block. I didn't bother trying to get the old one out until I see the new part for fear of causing more damage.
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  2. Seatman

    Seatman Active Member

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    I would expect it's a standard thread into the block, can't see any reason why it would be reverse but other than that you're the first one I've heard of to break it. That deserves a point :D
  3. chittychittybangbang

    chittychittybangbang Administrator

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    You should also be able to find a stud install tool at a local shop. Or thread 2 nuts against each other on the stud. And be careful with the wrench!
  4. YMZ

    YMZ Super Moderator

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    There's no reason for it to be a reverse thread...

    I'm surprised they can get a replacement in one day... When I ordered spares, several timing belt changes ago, they took about a week to arrive...

    Practice your patience until you get started removing the broken stud... Some people have the knack for getting broken bolts and studs out, others (like me) have a bad time of it...

    Good luck !!!!!!!!!!

    Yuri
  5. Seatman

    Seatman Active Member

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    Also good to sometimes use a short ratchet, that way you can feel when it's getting a bit tight lol:D
  6. Fingers

    Fingers Member

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    I thought about the double nut thing for the install and since I have to buy a new nut for both the idler AND the tensioner (since I had to remove it again), I`ll have two. Of course it`s not a reverse thread or it would twist out when you thread the bolt on it. I think I may have gone slightly insane for a little while after it snapped and I had to pull everything apart again. I quaffed a good portion of a six pack of Sam Adams so I`m okay now.

    I don`t know what the issue was with the torque wrench. I left it on the same setting and tried it on a lug nut and it worked fine. The only thing I can think of is that I wasn`t holding it straight on the bolt from my awkward angle under the car and that may have made a difference.

    The dealer I ordered the part from is in Winnipeg and the part is in Toronto. I`m sure I`ll be paying a premium price for the rush order. Any guesses on how much they can soak me for a threaded pin and new nut.

    So I`ll take my dummy point from Seatman and give it a go again likely on Saturday, weather permitting.
  7. Keithuk

    Keithuk Super Moderator

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    I don't know what happened to your torque wrench unless you have the one where the drive square pushes through to change direction and you knocked it through without knowing, there should be an arrow showing the direction.

    Didn't Jettagirl have a broken stud when she do her timing belt, I think she was using an air wrench to tighten hers?

    You shouldn't need to buy another nut to lock the stud in as there are loads of nuts the same size on your car just borrow one of those to tighten the stud?
  8. YMZ

    YMZ Super Moderator

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    Yes... I believe that the nut that's supposed to hold the tensioner (and idler???) in place is a lock-nut... use a regular threaded nut (or, rather, pair of nuts) to screw in the new stud - unless you happen to own one of those specialized stud fasteners... (I have one left over from my youth... don't think I ever used it...)

    Yuri
  9. Fingers

    Fingers Member

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    I think the mystery has been solved. It wasn't the torque wrench at all. I did a search in my Bentley manual for the torque spec but didn't check that the information it gave me was for a different engine. It told me to torque the nut to 40Nm (~30ft-lbs). I think that's way too high and the torque wrench simply didn't get to the proper torque before the stud failed. Now I'm trying to find the proper spec but I'm having a hell of a time finding it in the manual. Anyone know off the top of their heads?
  10. YMZ

    YMZ Super Moderator

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    On the BEW engine, the idler (13mm nut) is spec'ed at 18 Ft*Lbs...

    (The tensioner is spec'ed at 15 Ft*Lbs plus 45 degrees...)

    Yuri
  11. chittychittybangbang

    chittychittybangbang Administrator

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    All the torque specs are at the end of this article: http://www.myturbodiesel.com/1000q/a4/vw-jetta-tdi-timing-belt-change-replacement-bew-engine.htm, have you reviewd it?
  12. Fingers

    Fingers Member

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    I did review the article, rather extensively. It was an immense help. I thought it was very well written and documented but I still can't see where it indicates the torque on the idler. At the end of the article there is mention of removing it but not of re-installing it. It ends with a link to the installation article. Am I missing something at the end?
  13. chittychittybangbang

    chittychittybangbang Administrator

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    Yes, read the installation article that it links to ;)
  14. Fingers

    Fingers Member

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    Well, I'll be a horse's ass. I didn't think to go beyond the point that the idler would have been installed. I must have looked a half dozen times to the entire first article and only half of the second.

    Now the problem is that the article says 15 ft-lbs and Yuri says 18. Guru fight?
  15. Seatman

    Seatman Active Member

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    16.5 is the right one:D
  16. YMZ

    YMZ Super Moderator

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    ChittyChittyBangBang - please verify torque spec.

    I have 18 Ft*Lbs listed for the idler, as stated above... (in several sources...) - but I have one copy of the Bentley that lists it as 15 Ft*Lbs...

    CCBB has 15 Ft*Lbs in the referenced link...

    I wonder who else can chime in with a number...

    Yuri
    Last edited by a moderator: Aug 20, 2011
  17. chittychittybangbang

    chittychittybangbang Administrator

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    The service manual doesn't even say to replace that idler pulley let alone its torque. Shows you what you get for an $80 manual. However, the service manual for older PD engines with a very similar setup says 15 ft-lb so that's what I put in the article. If someone has a newer official reference I would gladly update what the article says. 18 is also fine, 3 ft-lb on that pulley won't damage it and a torque wrench might even be a little off. 30 ft-lb may damage it ;)
  18. YMZ

    YMZ Super Moderator

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    I'm perfectly OK with Seatman's recommendation...

    However, I was thinking: If Fingers over-tightened that nut enough to break the stud, is there any chance that the bearing in that idler may be damaged? (I know it depends on how it's constructed, but... I'd check over how that idler "feels" when turning, before re-installing it...)

    Yuri
  19. Keithuk

    Keithuk Super Moderator

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    Autodata says

    Tighten tensioner pulley nut. Tightening torque: 20 Nm + 45° which is 14.7 lbs/ft so 15 lbs/ft + 45° is close.
  20. Fingers

    Fingers Member

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    I doubt there will be damage to the idler since there was no pressure on the outer bearing cage. It was all on the center race which is in effect just a hollow tube. I didn't actually reach 30 ft-lbs so that would be a fairly small compression force on the center of the bearing relative to the twising force exerted on the pin. I can't see the inner stainless race having been deformed by the pressure but your point is well taken. I'll be sure to check operation of the idler before I reinstall it. I bought a new 3/8" torque wrench yesterday so I don't have to use the 1/2" monster. Finer touch and all, you see.

    Here's something scary. I ordered in the idler and the bolt but not the bolt for the tensioner. I had already given it the +45 so it had to be replaced upon removal. The dealer doesn't stock that bolt. Special order. I went to another dealer in the city and was able to get a bolt for the tensioner, but they didn't have one for the idler. Do these guys special order the parts every time someone wants a timing belt done or do they reuse the parts? At least I'm okay between the two dealers, but it sure reinforces doing my own work.

    I'll torque the idler to 15 ft-lbs +45. The +45 will probably put it at 18.

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