Chrysler 1998 Voyager Service Manual page 89

NS
DESCRIPTION AND OPERATION (Continued)
(Fig. 8). The actuator assembly is mounted between
the height sensing proportioning valve and the actua-
tor bracket on the left rear leaf spring (Fig. 8). As the
rear height of the vehicle changes depending on the
load the vehicle is carrying the height change is
transferred to the height sensing proportioning valve.
This change in vehicle height is transferred through
the movement of the left rear leaf spring. As the posi-
tion of the left rear leaf spring changes this move-
ment is transferred through the actuator bracket
(Fig. 8) to the actuator assembly (Fig. 8) and then to
the proportioning valve.
Thus, the height sensing proportioning valve
allows the brake system to maintain the optimal
front to rear brake balance regardless of the vehicle
load condition. Under a light load condition, hydrau-
lic pressure to the rear brakes is minimized. As the
load condition of the vehicle increases, so does the
hydraulic pressure to the rear brakes.
The proportioning valve section of the valve oper-
ates by transmitting full input hydraulic pressure to
the rear brakes up to a certain point, called the split
point. Beyond the split point the proportioning valve
reduces the amount of hydraulic pressure to the rear
brakes according to a certain ratio. Thus, on light
brake applications, approximately equal hydraulic
pressure will be transmitted to the front and rear
brakes. At heavier brake applications, the hydraulic
pressure transmitted to the rear brakes will be lower
then the front brakes. This will prevent premature
rear wheel lock-up and skid.
The height sensing section of the valve thus
changes the split point of the proportioning valve,
based on the rear suspension height of the vehicle.
When the height of the rear suspension is low, the
proportioning valve interprets this as extra load and
the split point of the proportioning valve is raised to
allow more rear braking. When the height of the rear
suspension is high, the proportioning valve interprets
this as a lightly loaded vehicle and the split point of
the proportioning valve is lowered and rear braking
is reduced.
CHASSIS TUBES AND HOSES
The purpose of the chassis brake tubes and flex
hoses is to transfer the pressurized brake fluid devel-
oped by the master cylinder to the wheel brakes of
the vehicle. The chassis tubes are steel with a corro-
sion resistant coating applied to the external surfaces
and the flex hoses are made of reinforced rubber. The
rubber flex hoses allow for the movement of the vehi-
cles suspension.
MASTER CYLINDER
The master cylinder (Fig. 9) consists of the follow-
ing components. The body of the master cylinder is
an anodized aluminum casting. It has a machined
bore to accept the master cylinder piston and
threaded ports with seats for the hydraulic brake
line connections. The brake fluid reservoir of the
master cylinder assembly is made of a see through
polypropylene type plastic. A low fluid switch is also
part of the reservoir assembly.
Fig. 9 Master Cylinder Assembly
This vehicle uses 3 different master cylinders.
Master cylinder usage depends on what type of brake
system the vehicle is equipped with. If a vehicle is
not equipped with antilock brakes, or is equipped
with antilock brakes without traction control, a con-
ventional compensating port master cylinder is used.
If a vehicle is equipped with antilock brakes with
traction control, a dual center port master cylinder is
used.
The third master cylinder used on this vehicle is
unique to vehicles equipped with four wheel disc
brakes. The master cylinder used for this brake
application has a different bore diameter and stroke
then the master cylinder used for the other available
brake applications.
The master cylinders used on front wheel drive
applications (non four wheel disc brake vehicles)
have a master cylinder piston bore diameter of 23.8
mm. The master cylinder used on the all wheel drive
applications (four wheel disc brake vehicles) have a
master cylinder piston bore diameter of 25.4 mm.
When replacing a master cylinder, be sure to
use the correct master cylinder for the type of
brake system the vehicle is equipped with.
The master cylinder is not a repairable component
and must be replaced if diagnosed to be functioning
improperly
CAUTION: Do not hone the bore of the cylinder as
this will remove the anodized surface from the bore.
The master cylinder primary outlet port supplies
hydraulic pressure to the right front and left rear
BRAKES 5 - 7