1999 GMC C-SERIES lock

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4-7
Avoid needless heavy braking. Some people drive in
spurts
-- heavy acceleration followed by heavy
braking
-- rather than keeping pace with traffic. This
is a mistake. Your brakes may not have time to cool
between hard stops. Your brakes will wear out much
faster if you do a lot of heavy braking. If you keep pace
with the traffic and allow realistic following distances,
you will eliminate a lot of unnecessary braking. That
means better braking and longer brake life.
If your engine ever stops while you're driving, brake
normally but don't pump your brakes. If you do, the
pedal may get harder to push down. If your engine
stops, you will still have some power brake assist. But
you will use it when you brake. Once the power assist is
used up, it may take longer to stop and the brake pedal
will be harder to push.
Hydraulic Brake Systems
If your engine stops running, or if your primary brake
system stops working, your vehicle has a reserve power
assist system to help you slow down. Just slowly and
steadily apply the brake pedal until you can safely get
off the road. The pedal will seem harder to push down.
Don't pump the pedal; the system won't work well or at
all that way.You may find that the steering wheel seems hard to turn
when you're turning and braking at the same time. Also,
the PRIMARY BRAKE warning light may come on and
the warning tone may sound. This is normal because the
main hydraulic brake system and power steering both
use the power steering pump. If this ever happens, let up
on the brake pedal a little. When you let up on the brake
pedal in that situation, it lets the steering get a little
more help from the pump.
Anti-Lock Brakes (Option)
Your vehicle may have anti-lock brakes (ABS). ABS is
an advanced electronic braking system that will help
prevent a braking skid.
If your vehicle has anti-lock
brakes, this warning light on
the instrument panel will
come on briefly when you
start your vehicle.
When you start your engine and begin to drive away,
your anti
-lock brake system will check itself. You may
hear a momentary motor or clicking noise while this test
is going on. This is normal.
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4-8
If there's a problem with the anti-lock brake system, the
anti
-lock brake system warning light will stay on. See
ªAnti
-Lock Brake System Warning Lightº in the Index.
Here's how anti-lock works. Let's say the road is wet.
You're driving safely. Suddenly an animal jumps out in
front of you.
You slam on the brakes. Here's what happens with ABS.A computer senses that wheels are slowing down. If one
of the wheels is about to stop rolling, the computer will
separately work the brakes at each wheel.
The anti
-lock system can change the brake pressure
faster than any driver could. The computer is
programmed to make the most of available tire and
road conditions.
You can steer around the obstacle while braking hard.
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4-9
As you brake, your computer keeps receiving updates on
wheel speed and controls braking pressure accordingly.
Remember: Anti
-lock doesn't change the time you need
to get your foot up to the brake pedal or always decrease
stopping distance. If you get too close to the vehicle in
front of you, you won't have time to apply your brakes
if that vehicle suddenly slows or stops. Always leave
enough room up ahead to stop, even though you have
anti
-lock brakes.
Using Anti
-Lock
Don't pump the brakes. Just hold the brake pedal down
firmly and let anti
-lock work for you. You may feel the
brakes pulsate, or you may hear air exhausting, but this
is normal.
Braking in Emergencies
At some time, nearly every driver gets into a situation
that requires hard braking.
If you have anti
-lock, you can steer and brake at the
same time. However, if you don't have anti
-lock, your
first reaction
-- to hit the brake pedal hard and hold it
down
-- may be the wrong thing to do. Your wheels can
stop rolling. Once they do, the vehicle can't respond to
your steering. Momentum will carry it in whatever
direction it was headed when the wheels stopped rolling.That could be off the road, into the very thing you were
trying to avoid, or into traffic.
If you don't have anti
-lock, use a ªsqueezeº braking
technique. This will give you maximum braking while
maintaining steering control. You do this by pushing on
the brake pedal with steadily increasing pressure.
In an emergency, you will probably want to squeeze the
brakes hard without locking the wheels. If you hear or
feel the wheels sliding, ease off the brake pedal. This
will help you retain steering control. (If you do have
anti
-lock, it's different: see ªAnti-Lock Brakesº in
the Index.)
In many emergencies, steering can help you more than
even the very best braking.
Steering
Power Steering
If you lose power steering assist because the engine
stops or the system is not functioning, you can steer but
it will take much more effort.
On vehicles with hydraulic brakes, the power steering
and main hydraulic brake system both use the power
steering pump. See ªHydraulic Brake Systemsº in
the Index.
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4-10 Steering Tips
Driving on Curves
It's important to take curves at a reasonable speed.
A lot of the ªdriver lost controlº accidents mentioned on
the news happen on curves. Here's why:
Experienced driver or beginner, each of us is subject to
the same laws of physics when driving on curves. The
traction of the tires against the road surface makes it
possible for the vehicle to change its path when you turn
the front wheels. If there's no traction, inertia will keep
the vehicle going in the same direction. If you've ever
tried to steer a vehicle on wet ice, you'll understand this.
The traction you can get in a curve depends on the
condition of your tires and the road surface, the angle
at which the curve is banked, and your speed. While
you're in a curve, speed is the one factor you
can control.
Suppose you're steering through a sharp curve. Then
you suddenly apply the brakes. Both control
systems
-- steering and braking -- have to do their
work where the tires meet the road. Unless you have
four
-wheel anti-lock brakes, adding the hard braking
can demand too much of those places. You can
lose control.The same thing can happen if you're steering through a
sharp curve and you suddenly accelerate. Those two
control systems
-- steering and acceleration -- can
overwhelm those places where the tires meet the road
and make you lose control.
What should you do if this ever happens? Ease up on the
brake or accelerator pedal, steer the vehicle the way you
want it to go, and slow down.
Speed limit signs near curves warn that you should
adjust your speed. Of course, the posted speeds are
based on good weather and road conditions. Under less
favorable conditions you'll want to go slower.
If you need to reduce your speed as you approach a
curve, do it before you enter the curve, while your front
wheels are straight ahead.
This is especially important with a tractor
-trailer. Try to
adjust your speed so you can ªdriveº through the curve.
Maintain a reasonable, steady speed. Wait to accelerate
until you are out of the curve, and then accelerate gently
into the straightaway.
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4-11 Steering in Emergencies
There are times when steering can be more effective
than braking. For example, you come over a hill and
find a truck stopped in your lane, or a car suddenly pulls
out from nowhere, or a child darts out from between
parked cars and stops right in front of you. You can
avoid these problems by braking
-- if you can stop in
time. But sometimes you can't; there isn't room. That's
the time for evasive action
-- steering around
the problem.
In emergencies like these, first apply your brakes
-- but
unless you have anti
-lock, not enough to lock your
wheels. (See ªBraking in Emergenciesº earlier in this
section.) It is better to remove as much speed as you can
from a possible collision. Then steer around the
problem, to the left or right depending on the space
available. If your vehicle has anti
-lock brakes, you don't
need to release the brakes to maintain steering control.
An emergency like this requires close attention and a
quick decision. If you are holding the steering wheel at
the recommended 9 and 3 o'clock positions, you may be
able to turn it just enough to miss the object without
removing either hand. But you must act fast, steering
precisely. The more sharply you turn, the greater the
chance of a skid, a rollover or a ªjackknifeº with a
tractor
-trailer. Just as quickly straighten the wheel once
you have avoided the object.
The fact that such emergency situations are always
possible is a good reason to practice defensive driving at
all times and wear safety belts properly.
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4-14
Loss of Control
Let's review what driving experts say about what
happens when the three control systems (brakes, steering
and acceleration) don't have enough friction where the
tires meet the road to do what the driver has asked.
In any emergency, don't give up. Keep trying to steer and
constantly seek an escape route or area of less danger.
Skidding
In a skid, a driver can lose control of the vehicle.
Defensive drivers avoid most skids by taking reasonable
care suited to existing conditions, and by not ªoverdrivingº
those conditions. But skids are always possible.
The three types of skids correspond to your vehicle's
three control systems. In the braking skid, your wheels
aren't rolling. In the steering or cornering skid, too
much speed or steering in a curve causes tires to slip and
lose cornering force. And in the acceleration skid, too
much throttle causes the driving wheels to spin.
A cornering skid and an acceleration skid are
usually best handled by easing your foot off the
accelerator pedal.Of course, traction is reduced when water, snow, ice,
gravel or other material is on the road. For safety, you'll
want to slow down and adjust your driving to these
conditions. It is important to slow down on slippery
surfaces because stopping distance will be longer and
vehicle control more limited.
While driving on a surface with reduced traction, try
your best to avoid sudden steering, acceleration or
braking (including engine braking by shifting to a lower
gear). See ªDiesel Engine Exhaust Brakeº in the Index
for information about using the exhaust brake on
slippery surfaces. Any sudden changes could cause the
tires to slide. You may not realize the surface is slippery
until your vehicle is skidding. Learn to recognize
warning clues
-- such as enough water, ice or packed
snow on the road to make a ªmirrored surfaceº
-- and
slow down when you have any doubt.
If you have the anti
-lock braking system, remember: It
helps avoid only the braking skid. If you do not have
anti
-lock, then in a braking skid (where the wheels are
no longer rolling), release enough pressure on the brakes
to get the wheels rolling again. This restores steering
control. Push the brake pedal down steadily when you
have to stop suddenly. As long as the wheels are rolling,
you will have steering control.
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4-25
What's the worst time for this? ªWet ice.º Very cold
snow or ice can be slick and hard to drive on. But wet
ice can be even more trouble because it may offer the
least traction of all. You can get wet ice when it's about
freezing (32
F; 0
C) and freezing rain begins to fall.
Try to avoid driving on wet ice until salt and sand crews
can get there.Whatever the condition
-- smooth ice, packed, blowing
or loose snow
-- drive with caution.
Accelerate gently. Try not to break the fragile traction.
If you accelerate too fast, the drive wheels will spin and
polish the surface under the tires even more.
Unless you have the anti
-lock braking system, you'll
want to brake very gently, too. (If you do have anti
-lock,
see ªAnti
-Lockº in the Index. This system improves
your vehicle's stability when you make a hard stop on a
slippery road.) Whether you have the anti
-lock braking
system or not, you'll want to begin stopping sooner than
you would on dry pavement. Without anti
-lock brakes,
if you feel your vehicle begin to slide, let up on the
brakes a little. Push the brake pedal down steadily to get
the most traction you can.
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4-26
Remember, unless you have anti-lock, if you brake so
hard that your wheels stop rolling, you'll just slide.
Brake so your wheels always keep rolling and you can
still steer.

Whatever your braking system, allow greater
following distance on any slippery road.

Watch for slippery spots. The road might be fine
until you hit a spot that's covered with ice. On an
otherwise clear road, ice patches may appear in
shaded areas where the sun can't reach: around
clumps of trees, behind buildings or under bridges.
Sometimes the surface of a curve or an overpass may
remain icy when the surrounding roads are clear. If
you see a patch of ice ahead of you, brake before you
are on it. Try not to brake while you're actually on
the ice, and avoid sudden steering maneuvers.If You're Caught in a Blizzard
If you are stopped by heavy snow, you could be in a
serious situation. You should probably stay with your
vehicle unless you know for sure that you are near help
and you can hike through the snow. Here are some
things to do to summon help and keep yourself and your
passengers safe:

Turn on your hazard flashers.
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