This article is a reminder to check your brakes early this season. We
don’t want to let time get away from us in this critical area. Here are the
areas where I make a pre-season check:
- Pedal free travel
- The master cylinder fluid level
- Brake pedal firmness
- Hand brake operation.
Pedal Free Travel
Pedal free travel is very easy to
check and begins to suggest to me the maintenance level of my brake system.
This check takes less than a minute. When I have found incorrect free
travel, I’ve often found brake problems elsewhere.
There should be
about ½ inch of free travel at the beginning of the pedal stroke. This free
travel occurs before the master cylinder piston begins to move. Once the
free travel distance is set, it usually requires no further adjustment. If
the free travel is too long, the brake pedal firms up lower than it should.
If too little, the by-pass port of the master cylinder may be covered
leading to brake shoe drag.
I test free travel by hand so I can
better observe distance. I measure the distance from the pedal at rest to
the point of first resistance, keeping in mind there is a little resistance
at the top caused by the pedal return spring. The resistance I’m looking for
occurs when the push rod contacts the outer base of the master cylinder
As I was writing this article, I checked the free travel on
my TD and found it incorrect. The distance was at least one inch, twice the
correct distance. I also noted the pedal had a little looseness at the top
and from left to right, so I’m thinking the pedal arm bushings need replaced
and will check the return spring.
Pedal free travel is adjusted at
the back of the master cylinder where the piston rod enters the cylinder.
The adjustment is not difficult, but it must be done under the car.
Master Cylinder Check
On a TD or TF, the master cylinder is full when
the fluid level is about ½ inch below the bottom of the filler neck, as
shown in the workshop manual.
The standard for the TA, TB and TC is
to have the fluid level about an inch from the filler neck.
I tend to
overfill my master cylinder a bit; but I keep in mind the fluid should be
well short of the filler neck. Space is needed for the brake fluid to expand
as the temperature goes up. When I checked my TD master cylinder this
morning it was empty as I suspected.
Several months ago as I
inspected the car before I bought it, I’d seen the evidence of the leak. I
had noted the frame paint had bubbled around the master cylinder area. Now,
with the outdoor temperature rising, my garage is warm enough for work and
I’ll remove the master cylinder for inspection and later locate the leak.
When I find my brake fluid level below the expected height, I look for
signs of leaks, adjust the brakes, and recheck the fluid level in the master
My guide phrase for pedal firmness is
“solid resistance.” I prefer my brake pedal to become firm no lower than
about half way to the floor. Consider the total travel distance of the brake
arm to the floor, less the ½ inch of free play, is about 7 inches. When my
brake pedal firms up lower than expected, I want to find out why. My quick
test for the correctness of the rear brake adjustment is to partially apply
the hand brake and then step on the brake pedal to see if the pedal firms at
a higher level.
If I find my brake pedal exhibits a soft or spongy
feel, or requires pumping, I investigate. Often, I’ve found a soft brake
pedal has been caused by air in the brake fluid and corrected it by bleeding
the brakes. I’ll also look for leaks around the cylinders.
drive with such care these days, especially with my wife in the car, that
even when going fast I don’t test the capability of the brake system on the
road. Now and then I remind myself these cars perform well when pushed to
the limits. This leads me to occasionally test my brake system performance
at a large parking lot where there is ample room for safety.
to satisfy myself my brakes have the power to quickly bring the car to a
stop far faster than under normal conditions. I’ve also enjoyed finding how
fast my cars will stop, and keep in mind a well-functioning MG brake system
will allow me to lock up the wheels. I first test the handbrake. Before
doing so I ask myself, “how long has it been since the handbrake cable was
renewed?” What is the condition of the cables?
I want my handbrake to
be sufficient to enable me to stop the car in the event of a hydraulic brake
system failure. The handbrake has got to be more than a hill holder even
though the rear shoes provide far less power than the footbrakes. Whenever
I’ve tested my handbrake, I’m reminded of how slowly it will stop the car.
After checking the handbrake, I apply the brakes with increasing pedal
pressure to test whether the car is capable of stopping quickly and
- If I have a spongy feeling pedal or get a rising pedal when
it is pumped, I’m thinking there is air or water in the brake fluid and will
look for leaks and bleed the system. It’s also possible the master cylinder
cups are worn.
- If the brakes don’t produce a powerful stop, the rear
brakes may not be fully applied, the brake linings may be greasy, or the
brakes may not have been “bedded.”
- If the brakes drag, chances are it’s
the shoe adjustments. Other possibilities include the handbrake adjustment,
an overfilled master cylinder, limited pedal free play, seized wheel
cylinder, weak return springs on the shoes or pedal, or a plugged master
- If the brakes pull to one side, I’ll look at the front
drums, shoes and wheel cylinders.
Further Inspection and More
If it has been 10 years or more since a brake system has been rebuilt, I’m
thinking it’s again time for this maintenance. I also just asked myself,
“How long have the brake lines been on the car?” Steel brake lines rust from
the inside, so I may replace them as well. Next time, I’ll have notes about
what I’ve done with my brake system. Meanwhile, I’d appreciate hearing from
you if you have comments or questions. Have a great spring driving season
this year. I hope your car runs like a top!