It's been at least five years since my emergency brake started getting stuck
"on" if I left the car parked for a few weeks. Since I have drum brakes on
the back, the brake cable is attached to a lever on the hindmost shoe which
forces both shoes against the drum at the top, pivoting on the auto-adjuster.
There are a number of standard ways to release a stuck parking brake: applying
and and releasing the brake multiple times, lurching the car forward and
back, bouncing the back corner of the car with the locked up wheel up and
down, flexing the cable housing with your hand between the wheel and the
spreader (where the main cable terminates and a shorter cable goes to each
brake drum), rapping the backing plate with a hammer (but don't bend it)
and tapping the front of the drum with a hammer and punch if your wheel allows
you access. If all of these things fail to free the emergency brake completely,
you'll know because the tire will drag, or the car will stop too quickly
if you try to coast in neutral. You'll usually feel slack in the first few
inches of the brake lever if the brake isn't released fully.
A final trick if the wheel does turn, but with a lot of drag, is to drive
it around the block a couple times, stopping every minute or so to make sure
it isn't getting too hot (and burning your fingers if it is). But the time
comes when none of these quick-and-dirty tricks work, and the only solution
is to remove the drum and replace the brake cable and the return spring,
which needs to be strong enough to pull back the brake shoes when the brake
is released. The elegant (ie, proper) way to get the drum off is to back
off the self adjuster screw through the access port in the backing plate
behind the drum (over the axle and under the bleeder screw and hydraulic
line). This almost never works for me when I need it, either the auto-adjuster
is a little rusted or the force of the sticking emergency brake cable keeps
it from wanting to turn. So my solution is to cheat, which risks damaging
the seals on the wheel cylinder, but when I'm stuck, I'm willing to risk
it.
With a drum brake system, the rear wheel is mounted on studs pressed through
the drum. The drum is held onto the axle, a stub axle in the case of a front
wheel drive car, by a bearing and a single large nut. The bearing is what
keeps the drum centered on the axel and allows the wheel to rotate with the
minimum of friction.There's a keyed washer, sometimes called a thrust washer
since the wheel nut pushes it against the outer bearing which is thrust against
a tapered bearing race in the drum, and the wheel nut is locked from loosening
up by a castellated retainer and a cotter pin.There's no way to remove the
drum without removing the nut on the axle, and no way to access the end of
the emergency brake cable and the lever assembly without removing the drum.
Also, with the outer wheel bearing removed, it allows the wheel much more
play on the axle, and by tapping the drum with a hammer, you can usually
get the brake shoes to retract a little, even if the cable remains jammed.
But the way to gain a mechanical advantage to pull the drum off of jammed
shoes is to put the tire back on and shake it. You want to run at least two
lug nuts up reasonably tight, because if you try this with loose lug nuts,
you'll damage the threads on the studs. Don't go berserk on the thing or
you could damage the wheel cylinder. The video to the left shows the wheel
pulling off, along with the drum, and the shaking is important. If you just
tried to pull the drum with a puller, you'd almost certainly damage the brake
shoes, the drum lining, or blow the wheel cylinder. The shaking gets the
shoes to retract a bit, where you're dealing with a jammed parking brake
or frozen pistons in the wheel cylinder. So below we have a typical drum
brake system,mounted in place, and you can see all the grease on the axle
from the wheel bearings contrasted with the rusty, dusty interior. The narrow
sprint running horizontally just below the greasy axle is the emergency brake
return spring, and after 22 years (in this case), it's just run out of "oomph."
The bright colored piece that looks like aluminum is the self adjuster lock.
You can see that there's a spring holding it down on the geared part of the
self adjuster, and the lock keeps you from simply sticking a screwdriver
in through the access port covered by the rubber plug (in the picture back
a few squares), and backing off the mechanical spread of the shoes. I never
have any luck backing off the self adjuster in emergency situations, even
with the lock pushed back from the gear. The video below shows the hack way
of removing the whole assembly from the backing plate after removing the
retaining clips on the short springs that holes the shoes loosely against
the backing plate. Drum brakes are an interesting and cleverly designed system
that looks like it was thrown together, but has been in use for a long, long
time, and usually provides a better manual emergency brake than you get with
disc systems.
The next two videos show disassembling the emergency brake cable from the
shoes, so it can be replaced along with the spring. In this particular instance,
the spring is worn out and needs replacing, and the cable itself was a bit
frayed going into the sleeve that brings it to the drum. The video to the
lower left shoes removing the retaining clip or washer that holds the lever
into the shoe assembly. It can be surprisingly difficult to get the lever
out once the retaining clip is removed because the shaft can be oddly shaped.
The video below shows how you slide back the spring on the lever so you can
get the ball end of the cable out of the lever. When the spring is in good
shape, it takes quite a bit of force to pull it back, and you may feel like
it would be easier if you had three hands. In this case, the spring is so
worn that it was the easiest part of the job. As soon as I get the pictures,
I'll show getting the brake cord out of the drum and the adjuster under the
car. Replacing the cable is just a matter of reversing the steps.
The last steps in removing the emergency brake cable are unhooking it from
the spreader, removing the retaining clip that anchors the sheath to the
stub frame, and getting the spring and the cable end out of the drum. The
first step, removing the ball end from the spreader that is activated when
the driver pulls the parking brake lever up, doesn't require illustration.
The retaining clip pulled straight up from the the slot without trouble,
even though it hadn't moved since 1986.. What's much trickier is getting
the retainer out through the whole in the hub. In this case, it had three
tabs sprung out to hold it in place, and the shop manual suggest using a
small hose clamp to gather them it. I got two of the tabs started through
with the baby visegrips, and then got them out of the way and poked the third
on through with a screwdriver. On reinstallation, it's a good idea to feed
the cable with the ball end through the stub frame first, get the ball hooked
through the spreader, and then feed the other end through the drum. After
that you can install the outside retaining clip, then hook the cable up to
the lever that gets reinstalled on the shoe.
To the lower left, you can see the new emergency brake cable and spring
installed. I put it back together in reverse order of the video, starting
by hooking the cable up to the lever, then installing the lever on the brake
shoe, then installing the brake shoes on the backing plate. The problems
cam at what should have been the simple end, hooking the new cable up to
the emergency brake adjuster and spreader. The problem is that the slug on
the end of the new cable wasn't as wide as the ball on the old cable so it
simply pulled through the hole. To kludge it, I forced it back into the slot
section and filled the whole with a 1/4" bolt. I didn't realize until I got
home and looked at the picture that cable slug is actually caught between
the head of the bolt and the double nut. It works, but I think it will be
a better fix if I reposition the end of the cable to be next to the bolt.
Barring that, a washer or two wouldn't hurt:-)
