Frozen caliper bolts

Fisher, Scott Scott_Fisher at
Mon Jun 25 11:18:08 EDT 2001

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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