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Thread Repair Question #5190901 08/19/19 01:48 AM
Joined: Aug 2004
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The Critic Offline OP
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2004 Subaru WRX STi, 65K miles, with the Brembo Calipers.

Note: this car spent time in Alaska before it came to CA.

I was performing a front brake job (pads and rotors) and the upper caliper bolt (on the driver side) was seized into the caliper body. The bolt is a grade 10 M12X1.5mm bolt that is approx 45mm long. The bolt is steel and the caliper body is aluminum.

Somehow, I was able to remove the bolt without breaking it. The threads on the caliper side were almost gone. I ran my M12x1.5mm tap thru the damaged hole and after a few tries, some threads were "created." You can feel the threads but you can barely see them.

The bolt was ran thru a M12X1.5mm die several times and the threads look okay.

I threaded in the bolt and it went in smoothly. I was able to successfully torque the bolt to 80 ft-lbs.

Clearly, this was not an ideal repair. My questions are:

1) My "repair" allowed the bolt to be torqued to spec. When torquing the bolt, it felt normal. Should I just leave it alone or should I disassemble and repair properly?
2) I do not own a M12x1.5mm time-sert kit but I can buy one. However, would tapping the caliper with a SAE 1/2" die and installing the appropriate size/thread pitch bolt be an acceptable repair?

Thanks.

Some links to this issue:
https://forums.nasioc.com/forums/showthread.php?t=874551
https://www.iwsti.com/forums/gd-general/236287-attention-anyone-brembo-brake-calipers.html

Last edited by The Critic; 08/19/19 01:48 AM.

2011 Toyota Prius 1.8L - 206K - Valvoline Premium Blue Restore 10W-30
2007 Honda Accord 2.4L - 144K - Valvoline Premium Blue Restore 10W-30
Re: Thread Repair Question [Re: The Critic] #5190904 08/19/19 02:19 AM
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billt460 Offline
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Did you use anti seize when you reassembled it? If you did, and it felt normal when you were torqueing it, and not "mushy", I would say you're good to go. 80 ft. pounds is considerable torque. If anything was weak, especially in Aluminum, I would think you would have felt it, or else it would have simply stripped out.

Re: Thread Repair Question [Re: billt460] #5190910 08/19/19 02:45 AM
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The Critic Offline OP
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Originally Posted by billt460
Did you use anti seize when you reassembled it? If you did, and it felt normal when you were torqueing it, and not "mushy", I would say you're good to go. 80 ft. pounds is considerable torque. If anything was weak, especially in Aluminum, I would think you would have felt it, or else it would have simply stripped out.

I did not. It was originally intended to be a "test;" I was not expecting the threads to hold torque.

But since the threads held 80 ft-lbs, I considered it to be a miracle and would prefer not to disassemble at this point...unless you folks feel otherwise.


2011 Toyota Prius 1.8L - 206K - Valvoline Premium Blue Restore 10W-30
2007 Honda Accord 2.4L - 144K - Valvoline Premium Blue Restore 10W-30
Re: Thread Repair Question [Re: The Critic] #5190925 08/19/19 03:29 AM
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billt460 Offline
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I still wouldn't be worried. Just keep an eye on it for a while to make sure nothing starts becoming loose. Even if in the future it should come loose, or else strips out, it's not that big of a deal, or that expensive to have a shop install a Heli-Coil for a good, permanent fix. I would imagine a Brembo replacement caliper is quite expensive.

Re: Thread Repair Question [Re: The Critic] #5190934 08/19/19 04:14 AM
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Linctex Offline
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Originally Posted by The Critic
But since the threads held 80 ft-lbs, I considered it to be a miracle and would prefer not to disassemble at this point......

That is a miracle indeed.

Don't touch it until you have replacement parts in your hands.


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Thread Repair Question [Re: The Critic] #5190944 08/19/19 04:29 AM
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Donald Offline
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I would leave it as is. But be prepared for it to not torque properly in a future brake re-assembly. At which point I would probably get a new caliper. Although you could try a Heli-Coil.


2015 Ford F-250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: Thread Repair Question [Re: The Critic] #5191014 08/19/19 06:06 AM
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Trav Offline
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I couldn't let that go, heat is possibly going be a factor as aluminum expands much more than steel so the already damaged and weakened threads may expand and allow the bolt to loosen. It doesn't take lot of degrees for aluminum to expand.
Being an STI the chances of the brakes getting a workout and seeing higher temps is more likely than grandma in her grocery getter.

I would Time Sert it and use blue Loctite on all the bolts (not neverseize on brake bolts) as it also acts as a anti seize compound, many new bolts for calipers have it already applied in the form of a single use tape (usually rust colored).


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Re: Thread Repair Question [Re: The Critic] #5191032 08/19/19 06:45 AM
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mattd Offline
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Never use anti seize on caliper bolts. I would have put thread locker on it at it at least. It’s one of those things where yeah the repair worked, but will it last? It held up to the torque spec , but as Trav stated I would repair it by a time cert


2007 Ford F-350 4x4 6.0 PSD

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Re: Thread Repair Question [Re: The Critic] #5191098 08/19/19 08:04 AM
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WyrTwister Offline
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Might consider searching the salvage yards for a replacement part / parts . Just in case .

Best of luck to you , :-)


Wyr
God bless
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