Head stud is pulling out, won't torque
12-31-2011, 12:30 AM
#1
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Head stud is pulling out, won't torque
I'm in the middle of a HG change and found that the leak was actually a loose head nut (it was free spinning). I went to put everything back together and of course that same nut/stud won't torque down and I'm ending up with more threads above the nut. What are my options to fix this?
Last edited by audisport; 12-31-2011 at 01:05 AM.
12-31-2011, 12:41 AM
#2
Sounds like the stud is pulling out of the block. The aluminum threads in the block are likely damaged. Not sure how you would fix that. You might try double-nutting the stud and removing it, cleaning up the threads with a tap, and then bonding the stud in place with red locktite, epoxy or JB Weld. Not sure how much clamping force that will allow, though. The threads are so deep I don't think you could heli-coil it. Maybe someone else will have some better ideas. Good luck.
12-31-2011, 01:04 AM
#4
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Not sure I am following. If the stud won't turn when you double nut it, what is spinning when you try to torque the head down? Any chance the threads in the nut and/or at the top of the stud are stripped? That would be the easiest failure to fix -- just replace the stud and nut (use a collet style stud remover and a be t-breaker bar to get the stud out -- it's glued in place). If the stud is spinning in the block, then you'll most likely need to pull the stud and re-thread the block with an insert (Time-Sert would be best).
12-31-2011, 01:10 AM
#6
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Right. If that stud is not turning at all when double nutted, it looks like it was installed too high. As a result, the nut only had a few threads to grab onto and has stripped under the high torque and pressure it must hold. Take a look at the bottom few threads of the stud and the nut and see if they aren't stripped. You could probably get away with reusing that stud by pulling it out, cleaning the block threads out so the stud will install until it stands 72mm above the deck. Then when you install a fresh nut, it will be on the top (good) threads of the stud.
12-31-2011, 01:13 AM
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How many additional threads are past the nut now? Can you see if the threads are pulling from the block. You will need to take the head back off and shine a light down in to the area around the stud. A lot of aggravating cleaning will probably need to be done to get a good look.
I doubt it, but there is also the possibility the stud has broken or yielded.
If the threads are pulling from the block, short of replacing the block, your only reliable option is to repair them with a time sert or heli-coil (I'm a fan of the time serts).
As far as getting the old stud out, either double nut and thread it out or keep tightening the nut and pull it from the block.
I doubt it, but there is also the possibility the stud has broken or yielded.
If the threads are pulling from the block, short of replacing the block, your only reliable option is to repair them with a time sert or heli-coil (I'm a fan of the time serts).
As far as getting the old stud out, either double nut and thread it out or keep tightening the nut and pull it from the block.
Last edited by fortysixandtwo; 12-31-2011 at 01:17 AM. Reason: oops sert not cert
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12-31-2011, 01:15 AM
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Not sure that will work. The stud started out only 1 to 1.5 threads above the nut (which were all new). I didn't feel it torquing so I marked them to make sure it wasn't spinning. It wasn't so I actually doubled up a washer on this one (probably shouldn't have) to see if for sure that the bolt was pulling out. And evidently it is. So it's pulled out quite a bit compared to where it was. It sounds like I'm going to have to try and pull it and try the timesert.... and use a new stud.
12-31-2011, 01:16 AM
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Thread updates made while reading / typing.
Going by the picture, the threads are being pulled from the block. Is there still tension while tightening the nut?
Going by the picture, the threads are being pulled from the block. Is there still tension while tightening the nut?
12-31-2011, 01:20 AM
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The bolt is already pulled out from someone else that overtorqued it is my guess which is why the nut was spinning when I went to take it apart and cyl 4 was filling with coolant.
12-31-2011, 01:24 AM
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Unfortunately, just keep stacking washers and jack the stud out. Trying to rotate it may cause more damage. When the stud comes out, it will have a spiral of aluminum in the threads.
12-31-2011, 01:30 AM
#13
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Agreed. If it is moving up without spinning, then it needs to come out so you can repair the threads in the block. I've never done it with the motor in the car, but if you search here, I believe a few folks have said they were able to do it. I recall one person saying he used a regular old heli-coil and it held fine, but clearly a time-sert is the better option... Sorry 
12-31-2011, 01:34 AM
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