330 Auto Brakes
Figure 19-1. A—The vehicle’s automatic transmission is in
park. B—The parking brake has been applied and the warning
light is now turned on. (Toyota)
A
B
Park
Neutral
3RD/OD Gear
2ND Gear
1ST Gear
Reverse
Gear
Note: This test is not accurate on vehicles
with ratcheting foot levers.
Note: In some vehicles with rear disc brakes,
movement backward (with noticeable
resistance) may occur if the accelerator is
pressed. This is considered normal.
The parking brake is a relatively simple system that
seldom gives trouble. However, problems in the parking
brake can be difficult to isolate from other brake com-
plaints since they do not occur frequently. This chapter
builds on the information in Chapter 18 to identify com-
mon parking brake problems and service procedures.
Parking Brake Problems
The most common parking brake problem is failure to
hold the vehicle stationary. Poor holding power is most often
caused by misadjusted or worn service brakes. However,
stretched parking brake cables or bent levers can cause poor
holding even when the service brakes are in good condition.
If the parking brake suddenly becomes completely inopera-
tive, and the service brakes work properly, a linkage part has
broken or has become disconnected.
Another common problem is parking brake sticking.
Many drivers simply use the automatic transmission park
position or place a manual transmission in gear to hold the
vehicle. The parking brake is not always or seldom used.
Over time, the cables become dirty and corroded. If this
happens, the cables may not apply the parking brake or
will stick in the applied position. When this happens, the
vehicle cannot move, and the driver may blame the ser vice
brakes or possibly the transmission.
Another cause of sticking parking brakes is a broken
release mechanism. If the release lever is pulled and the
parking brake does not release, the linkage has probably
come loose. Some cable operated releases can stick or the
cable can break.
Warning light problems can result in the light not com-
ing on when the parking brake is applied, or staying on at all
times. Warning light problems are caused by a misadjusted
or defective switch, a blown fuse, or a burned out bulb.
Diagnosing Parking Brake Problems
To diagnose parking brake problems, you need to
determine whether the problem is in the parking brake
linkage or the service brakes. Once you have done this,
then you can proceed to check individual components.
Parking Brake Performance Test
The simplest way to diagnose parking brake problems is
to perform a parking brake performance test. Start by driving
the vehicle to a spot with enough room to allow it to move
forward. Then perform the following tests depending on
whether the vehicle has an automatic or manual transmission.
Click Test
The first test can be used on vehicles with either a
manual or automatic transmission. This test is the so-called
click test. Simply put, you either pull or push the parking
brake pedal or lever, apply and count the number of clicks
from the mechanism until it stops. If you count more than
8-10 clicks, the parking brake is in need of adjustment.
Automatic Transmission Vehicles
Stop the vehicle, place the transmission in Park, and
leave the engine running. Apply the parking brake and
note whether the warning light comes on. See Figure 19-1.
Then place the transmission in Drive. If the vehicle has
an automatic parking brake release, use your foot to hold
the parking brake in the applied position; do not apply the
service brakes. If the vehicle moves when the transmission
is placed in Drive, the parking brake is not holding. Next,
release the parking brake. The warning light should go out
and the vehicle should idle forward. If the vehicle does not
move easily, the parking brake is sticking.
If the release mechanism is a manual type, ensure the
ratchet and pawl assembly holds the lever in the applied
position when you remove your hand. Check that the pawl
disengages easily when you operate the release handle or
button. If the vehicle has a vacuum release parking brake,
ensure that it holds in Park with the engine running and
releases when the shifter is moved to the Drive position.