Despite the use of threadlocker being somewhat widespread (e.g. repair videos), I have yet to see a single recommendation to use it in any service manual. Perhaps this is my relative inexperience, but I thought I'd ask the community out of curiosity - do you use threadlocker? If so, what is your criteria for deciding which bolts receive threadlocker and which ones do not?

2 Answers 2


It depends on the vehicle but it's not uncommon to see threadlocker specified for assembly.

Use threadlocker when it's called for. Today many modern vehicles use one-time-only fasteners instead of threadlocker so it may be less common now than it was in the past.

I use threadlocker when the service manual says to, I replace fasteners when called for, and I just torque to spec when that is all that is specified.

  • I'm not quite sure where you're coming up with a correlation between using threadlocker and one-time-only fasteners? Apr 30, 2022 at 23:40
  • 1
    I've known of some people who will reuse one-time fasteners and assume that if then just put threadlocker on them it will be ok. That's NOT the case. But some folks just do what they want.
    – jwh20
    Apr 30, 2022 at 23:43
  • One-time-fasteners are usually torque-to-yield, which don't use threadlocker. Apr 30, 2022 at 23:46
  • @jwh20 Ahh ok. I guess it's just the cars I've worked on in which I've seen no mention of threadlocker in a manual.
    – TLex
    May 1, 2022 at 0:36
  • @Paulster2 - Only other one-time fasteners I can think of are exhaust bolts/studs, but I also haven't seen threadlocker prescribed for those.
    – TLex
    May 1, 2022 at 0:40

The main places I have seen the required use of Threadlocker or Retaining Compound (e.g. Loctite 638) specified in a car repair manual is on the splines of driveshafts.

I have also seen a band of threadlocker already in place on new bolts that are used to hold brake callipers on.

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  • Damn, well that makes it easy.
    – TLex
    May 2, 2022 at 10:03

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