Frozen caliper bolts

Kneale Brownson knotnook at
Mon Jun 25 17:40:04 EDT 2001

Kano Laboratories   is your direct-order source 
for Kroil.  Kroil has helped me take apart several rusted threaded items 
that I couldn't budge with WD40/Liquid Wrench, despite soaking repeatedly.

At 10:18 AM 06/25/2001 -0700, Fisher, Scott wrote:

>Michael Williams asks:
> > I have my 89 100 up on jacks at the minute and I've run into a snag in
> > replacing the rotors. It seems like the caliper carrier bolts are
> > frozen. I've soaked them with WD-40 and pulled on them pretty good but
> > they are not moving.
>Sorry about the length of this, and I hope it does some good for other
>Badly frozen caliper bolts (or any bolts, for that matter) mainly take
>patience, used in combination with a suitable application of force,
>vibration, heat, penetrating oil, and leverage.  But of these, patience can
>be the most important.
>WD-40 is about the weakest of the penetrating oils on the market; there's a
>variety called KRoil (spelled with the two upper-case letters) that works
>much better.  And I finally had to throw out my empty can of "Knock'er
>Loose," a product that my wife purchased for me at a more trade-oriented
>auto parts store.  Time to find a KRoil distributor, I guess.
>Anyway, back to your 100:  If you can't or won't use heat on the frozen
>bolts, and don't have an impact wrench, you can build your own impact wrench
>from a sufficiently large hammer and a proper breaker bar.  I use the
>1 - a 4-pound hand drilling hammer (sometimes called an engineer's hammer),
>immediately christened Mjollnir (Per will get it :-).  It has a massive
>ovoid head, a short handle, and delivers an incredible amount of force
>without having to really slam it hard.  I find that this avoids most of the
>danger of hammering on car parts; use a lot of mass and just enough force to
>get it moving, reserving most of your muscular control for accuracy.  Works
>better and does a lot less collateral damage.
>2 - a solid -- that is, non-ratcheting -- breaker bar.  The one I use for
>big whacks has a 1/2" head and a 1/2" bar (about 12" long) that slides
>through the back of the head.  I also have a 3/8"-drive breaker bar where
>the handle simply pivots, but for frozen brake calipers I'd use the big one.
>That's your home-built impact wrench.  As the court of last resort, I find
>that the following part usually finishes the job:
>3 - a three-foot length of pipe, with an internal dimension suitable for
>slipping over the handle of your breaker bar.  The first time I used this to
>remove some hopelessly rusted-on chunk of metal from the old British sports
>car I was repairing at the time, I was moved to verse:
>   I'm greatly indebted to Archimedes:
>   Thanks to him, I don't have to eat my Wheaties.
>The real trick is to cycle through the application of oil, vibration, and
>leverage until it works -- that's the patience part of the equation.  Squirt
>on the penetrating oil, then put the socket on your breaker bar and beat on
>it with the big hammer for a minute or two.  You may also find it useful to
>take a flat punch or drift and tap directly in the center of the bolt head;
>the idea is to crack the rust seal in the threads with vibration, and also
>to drive the penetrating oil farther into the joint.  If it doesn't start
>loosening, slip the pipe over the bar and haul on it with all your might.
>(I find it works best to orient the bar so that I pull UP on the bar to
>loosen the nut -- that is, stand in front of the wheel center on the right
>side and in back of it on the left side -- because the car weighs more than
>I do.)  If that doesn't work, spray, whack, and pull; spray, whack, and
>Now, for the heat part of the equation: Using open flame on your car is
>quite frightening, and rightly so.  It's dangerous.  It would be sensible to
>have a fire extinguisher on hand if you place a butane/propane torch on any
>part of your car.  And you're correct in assuming that the WD-40 will
>ignite.  That's scary, too, the first time it happens.  Fortunately, when it
>happened to me, it burned off quickly and I actually ended up learning to
>"blow out" the fire with the torch.  (Insert huge disclaimer here: if you
>burn down your car, house, or neighbors, remember I told you it was
>dangerous!)  If I were stuck with using a torch to try to loosen stuck
>caliper bolts, I would -- in addition to the precautions of a fire
>extinguisher and EXTREME caution in where I pointed it -- make sure the
>rubber brake lines were well out of the way before hitting the caliper bolts
>with the torch.
>Finally -- and this may be a "well, DUH" but it's caught me once or twice --
>make sure you're getting the penetrating oil on the threads of the
>connector.  That is, if you spray a gallon of stuff on the head of the bolt,
>but the threads are way down on the other end, you'll do nothing but clean
>the bolt head.  It may take some wiggling and judicious use of the little
>red spray-nozzle extender to get the penetrating oil onto the threads, but
>it's worth it.
>--Scott Fisher
>   Tualatin, Oregon

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