Loctite with HeliCoil?

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Mar 25, 2007
Buffalo, NY
I just finished doing the dreaded (to me at least) repair of the brake caliper bolt hole with a helicoil kit. Not that hard of a repair, the worst part was getting the drill started to ream out the hole to the proper size. Until you get about 1/8" in all it wants to do is grab an edge and yank the drill out of your hand. After that the rest of the process is without drama (easy, bordering on pleasant)!

OK, now to my question...
Is it OK to use loctite when installing the bolt?? Seems like I read somewhere that you can't or don't want to, I tried a search with helicoil and loctite and it turned up nothing either way. My instincts tell me a small amount put into the helicoil would run down in between the coil and the threads cut into the hole and another small amount on the bolt would secure it to the "inside" of the coil. My main motivation is a desire to fill gaps in so saltwater won't find its way in there as I live in the rustbelt, so I try to use either loctite or anti-sieze on all my fasteners.
Personally, I use green Loctite when installing a Helicoil; don't want them to ever come out. Makes a good lube for the Helicoil to go in smoothly too. Depending on the application of the bolt and repaired hole, I will use blue Loctite on the bolt if I don't want it to vibrate out. For any other application, anti-seize is fine.
Learned something interesting thing about Loctite when a rep came to our work. The bottles of Red 262and Blue 242 say High and Medium strength but according to the rep they are actually formulated according to bolt size (has to do with the tiny gaps in the threads). Size reccomendations are even written on the bottle but in tiny letters. Same stuff just different viscosity. Rep didn't have a reason why they do this

As for your helicoil, I would have glued it in with a loctite product by itself. Let it dry then install the caliper bolt dry. Unless you have a problem with loosening of the caliper bolts there isn't anything to be gained (just my opinion) by using loctite on the threads. 90 lbs of torque is what keeps it locked in place. I have never found a loose caliper bolt during maintenance.

Helicoils come over-sized, they actually compress as you install them. Because of this spring tension against the tapped hole and the fact that Lock-tite is anerobic (only cures in the absence of air) I've never used it with a heli-coil. I just didn't see it curing correctly, if at all, around what is essentially a coil of wire.

Agreed that the proper install torque should be enough to keep the bolt from working loose. If that doesn't make you all warm and fuzzy then I would suggest either making a sheet metal lock-tab for each pair of bolts, or drilling the bolt heads and safety wiring them. In some sizes Heli-coil offers or used to offer a prevailing torque locking insert. The thread insert has (had?) slightly deformed coils near the bottom of the insert designed to act like a nylox or similar nut. Based on that and their normal instructions for a dry install I'm even less inclined to use a thread locker during the install of the insert. They're not common kits and I can't recall when I last saw such a kit for sale.
Helicoils are OK, but timeserts are the BOMB!

Yeah, proper torque usually does it for me, I just mainly feel like I want to fill in some of the gaps to keep moisture out. I'm for sure not gonna remove the heli, maybe I'll see if I can buy some of the loctite green locally, if not, well one way or another it's assembly time tonite

Gotta agree Dynosoar, my cheapness got the better of me, one of my buddies has a race car (a Ford Escort!!! ??) & he swears by 'em. And oh yeah, he takes a whole lotta crap for his choice in race car.
"Let it dry"

err, that might be the problem here- as nt says above, the stuff only hardens with NO air.

So you'll put the bolt in, that'll kick it- and then the bolt will probably pull the insert out when you
remove it next.

Agreed about Timeserts/Tineserts/etc- "like it never happened"- well, as long as there's enough meat
to install it in the first place...

"Let it dry"

Actually Loctite will dry, but slowly in the air. Also contact with metal triggers a reaction. Thats why you are not supposed to touch metal with the tip of the dispenser of the liquid versions of Loctite. Yes it's anerobic but it also requires the presence of metal. Put regular loctite on plastic threads and it doesn't work.

Ever wonder why the tip gets clogged up? Probably touched some metal at some point. I am guilty of this as well. Also depends on the type of metal, as some metals require primer before using threadlocker, such as aluminum and stainless steel.

This is straight out of some Loctite guides I have and also was stressed by a Loctite rep.

As for my comment about let it dry, it was about letting the loctite under the helicoil dry...

"Also contact with metal triggers a reaction."

hmm, you learn something new every day.


"Also contact with metal triggers a reaction."

hmm, you learn something new every day.


That part I knew, but tend to forget. Repeatedly.

When I worked for wilwood they used Timeserts for all of the threads used in clamping on the CNC production tombstones (several to many in and out cycles per shift). They are better than a Helicoil by a lot, but as pointed out, they do need more meat around the hole. And they are more $$ than a Helicoil.
The more I learn the less I really know....

Timecert kits are considerably more $ than a Helicoil, and not worth it for a caliper repair.

Loctite on the Helicoil to caliper repair, may or may not help, but if you loctite the caliper bolt in, almost assuredly the HC will come out when you next try and remove the bolt.

The Green Loctite is supposed to capillary into the fix, so can be applied after the insert in locked in place. You might try some of that on the outboard side of the caliper bolt hole, before the bolt is installed (to lock the insert...)

Good luck.
I had heard that about the metal, but never sure if it was proven or just an old mechanics tale... haha

My son called on his way home from work just after my post yesterday, "aaaahhhhh, what're ya doin' tonite???"

me: "workin' on the 60, why?" (knowing full well that I'm no longer workin' on the 60 tonite!)

"I'm at the parts store getting new pads & rotors for my cube van, wanna help put 'em on??"

"oh good, get a tube of loctite GREEN" extra long pause here to allow for squirming at his end... "um sure I'll give you a hand, already got my work clothes on"

So for those that like to know the end of the story...

I put some green on the coil and it is drying, will use green as well when I put the bolt in to get the same bond strength & I don't really care if the coil comes out on disassembly cuz I have 5 more of 'em in the kit I bought!

AND like a good dad, we got the new pads on his work truck, didn't need rotors!!!
If your objective is to keep salt water out of the threaded area, why not put a little silicone rtv in the bolt hole and on the threads?

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