6

Usually the issue is them getting rusted into place and breaking on removal. Well, I have the opposite problem. Properly installed and torqued studs with nuts are loosening themselves... The nut is staying in the position it was tightened to, but I've had the stud itself walk out multiple times now. It tightens in nicely and will be fine for several weeks. Then all of a sudden it has walked out (I'll find it hanging on by just a couple threads, or like last night where it was just sitting in there all the way out of the threads!).

Book seems to suggest the clean & dry plus torque is appropriate, but that's obviously not working. Are there any high enough temperature, but relatively low removal force (blue at best) threadlockers that can tolerate the heat that an exhaust manifold stud will see?

5
  • 1
    Oddly, in my case the nut does not appear to be moving. The marks on it stay lined up. It's the whole stud walking out. Especially odd as the threads appear to be perfect and it torques down just fine. Nov 14, 2017 at 17:23
  • Loctite® but not sure if it could handle high heat applications. Nov 14, 2017 at 17:23
  • I've seen that some kits include lock washers, do yours? Something like these would work to give some support given enough thread clearance... Nov 14, 2017 at 22:30
  • 1
    Have you got the right studs? Not mixing metric and imperial sizes or anything weird? You might benefit from replacing the studs, if they're a bit worn-looking could allow play, or just use a small amount of red loctite to fasten them into the block. Or do a clayton's repair and turn the stud end for end in the block.
    – Criggie
    Nov 15, 2017 at 0:18
  • I'm considering buying replacements to see what happens, but the current one is indeed the correct size and is showing no wear. However, something has obviously changed as it was in place for years but has just recently started vibrating out. Historically I've had a lot of problems with new parts vibrating out as the surfaces are so slick. I expect a new one to make the problem worse. I'm currently trying to identify any reason I might have excessive vibration. Nov 15, 2017 at 16:06

3 Answers 3

7

According to their datasheets Resbond 970TS is capable of withstanding 2100°F

Another method would be the use of locking wire on the studs

3
  • Great suggestions. Nov 14, 2017 at 18:13
  • Now I just need to find someplace that would sell me some in a reasonable quantity... :-) Direct orders have a $100 minimum and look like they have to be done on a PO. Nov 20, 2017 at 13:22
  • @BrianKnoblauch order $100 in Resbond and sell the rest on EBay :)
    – Martin
    Nov 20, 2017 at 14:30
1

If the stud is torque-to-yield by design, you need to replace them with new ones as they have stretched. https://en.wikipedia.org/wiki/Torque-to-yield_fastener

I know that generally in the engine community, they use anti-seize and not thread-locker. Thread-locker over time with corrosion can cause the stud to be permanently seized (regardless of thread-locker strength) causing it to snap on removal when you try to break it loose.

Using lock wire as suggested by @Myself in an answer below would be preferable to using thread-locker but I suggest you seek out the cause of the stud no longer gripping the threads mechanically.

5
  • 1
    I agree, it is very odd that the studs are moving. Something is wrong here
    – Martin
    Nov 15, 2017 at 11:09
  • They are not TTY. I like the lock wire idea, but it looks like a major challenge to implement in that location. Nov 15, 2017 at 16:03
  • @BrianKnoblauch Have you inspected the hole? Threading damage is a possibility. Have you tried new studs and nuts? Easy way to verify they have not been over-torqued and stretched. Also, I would ask how much torque are you securing them with? Whatever the "book" may be recommending may be too low. The "s indicating that I would not trust anything outside of a manufacturer service manual. Nov 17, 2017 at 0:52
  • It's very difficult to see into the hole (without dropping the engine), but from what I can see and feel (via tools) I can't find anything wrong. Securing at 49 N-m per the factory manual (there are 2 places in the manual with torques for that location and they match). Nov 20, 2017 at 13:21
  • Even with an inspection mirror? Not quite the same but I have seen spark plugs walk right out from slightly damaged threads. Even with limited access, you could just re-thread it with a tap and die to the correct spec and see if you scrape anything undesirable out. Nov 22, 2017 at 5:13
1

I just couldn't bring myself to spend the $$$ for Resbond 970TS (which also has the downside of a 6 month shelf life). Instead I opted for Rocksett (cheaper and does not have the short shelf life) which seems to be working fine so far. I put it on 5 days ago and have seen no rotation since.

1
  • 1
    It has now failed. Let loose 4 days ago. So, lasted about 3 and a half months. I thoroughly coated the stud in Rocksett, let it dry the prescribed time, and that lasted all of 2 days this time around... Mar 22, 2018 at 22:36

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .