Gimme a brake!!
My dad and I
were car nuts together when I was young and starting to drive. He was a Buick
lover (1938 was his favorite), of course, I loved LaSalles.
His spoken theory was that you could
forgive an awful lot in a car if it would start good, stop good and not
overheat. We have talked a lot about overheating and about some tune-ups, so I
guess it is time to talk about brakes.
We will be talking primarily about
’30s and ’40s hydraulic systems typical on LaSalles and Cadillacs, however,
many principles will apply to later models prior to power brakes.
Braking comes when brake shoes are
pressed against the brake drums. Both are dependent on each other for maximum
efficiency. If you let your shoes wear down too far or get dirty, the drums can
get scored and require turning down or replacement.
When you reline your brakes, always
make sure each shoe is properly arced to its own drum. Failure to do so will
greatly reduce efficiency because of uneven surface contact. You will also
cause rapid lining wear. Any good brake shop can do this and you should insist
on it. Relining without rearcing just means wasted money and will cause you to
have to do it all over much sooner.
OK, now you have good drums and
lining, let’s move on to the hydraulic system. You can still buy master
cylinder and wheel cylinder rebuilt kits across the counter for most of these
old cars. Rebuilding the master cylinder is not really difficult, but must be
done right.
After disassembly and cleaning of
the master cylinder, it needs to be honed. Don’t overdo it! You only need to
get it smooth in the area where the rubber cups travel. In most of these older
cylinders, you will have a small rust spot in the center of the cylinder where
moisture settles over the years.
When you hone these out with a fine
brake hone, you will get a better, more even surface by having the cylinder
submerged in cleaning solvent. Keep the hone moving steady and even, and don’t
stop the hone in the cylinder. Inspect and make sure it is smooth and clean.
When you are satisfied, then make sure both ports between the reservoir and the
cylinder are clean. This is important!
Then dry the cylinder well with
compressed air and use a heat gun. Check the ports again. Liberally clean the
insides of the cylinder again, this time with brake fluid and blow dry again.
This will clean out any foreign material.
When you are ready for reassembly of
the master cylinder, make sure you liberally coat all of the inside of the
cylinder as well as all parts going into it, with fresh brake fluid.
When you reassemble the cylinder, it
is a good time for a little extra insurance and install a new stop light
switch. Make sure all connections are good and tight, and install the master
cylinder to the frame before you hook up the hydraulic line; and assuming you
have the wheel cylinders off, you should use compressed air to blow out all the
brake line.
Now is the time to hook up your
brake lines and fill the master cylinder with brake fluid, and let it set and
soak while you finish the rest of the brake job. Cleaning and honing the
individual wheel cylinders is simple and nearly identical to preparing the
master cylinder. Clean up the backing plates and install the wheel cylinders
and you are ready to start the assembly of the brake system.
Follow your service manual for
reassembly. Make sure when you assemble the brake mechanism that the star wheel
adjustments are all the way in and the eccentric pivot is loose; otherwise, you
may have trouble getting the drums over the new linings.
Before you put the shoe and lining
assemblies on the backing plate, be sure you lightly lubricate the ridges on
the backing plates where the shoes ride. Failure to do so will cause some real
strange noises when you apply your brakes and release them.
Once you have the brakes all
assembled and the drums on, it is time to bleed them. It is a good idea to
fully flush the system and even waste some brake fluid doing so. To do this
right, you should use a pressure bleeder or have two people doing the job. when
you bleed the brakes, always start with the wheel farthest from the master
cylinder and finish with the closest. Usually, this will be right rear, left
rear, right front, left front.
It is also a good idea to go through
this procedure twice. The first time is primarily to flush and clean the
system, and the second time to make sure no air bubbles are in the system.
Now we are ready to adjust the
brakes—but we have run out of space, time, etc. due to all the news on our
regional show in this issue, so next month we will talk about how to properly
adjust your new brakes or even your old ones if they are still good and only
need adjusting.
You know, every time I work on
brakes or think about it, I remember one of my favorite cartoons that has even
been made into posters. It pictures a rustic, old, grizzly cowboy on his horse
that has fallen over a cliff. He is in the saddle pulling hard on the reins,
and is yelling to his horse “Whoa you SOB, WHOA!!!”
See ya next month.
—Walt