Chrysler New Yorker. Manual — part 25
BRAKE ROTOR THICKNESS AND RUNOUT
Any servicing of the rotor requires extreme care to
maintain the rotor within service tolerances to
ensure proper brake action.
Before refinishing or refacing a rotor, the disc
should be checked and inspected for the following
conditions:
Braking surface scoring, rust, impregnation of lin-
ing material and worn ridges.
Excessive lateral runout or wobble.
Thickness variation (Parallelism).
Dishing or distortion (Flatness).
If a vehicle has not been driven for a period of
time, the rotor surface will rust in the area not cov-
ered by the brake lining and cause noise and chatter
when the brakes are applied.
Excessive wear and scoring of the rotor can cause
temporary improper lining contact if ridges are not
removed before installation of new brake pad assem-
blies.
Some discoloration or wear of the rotor surface is
normal and does not require resurfacing when lin-
ings are replaced.
Excessive runout or wobble in a rotor can increase
pedal travel due to piston knock back. This will
increase guide pin bushing wear due to tendency of
caliper to follow rotor wobble.
Thickness variation in a rotor can also result in
pedal pulsation, chatter and surge due to variation in
brake output. This can also be caused by excessive
runout in rotor or hub.
Dishing or distortion can be caused by extreme
heat and abuse of the brakes.
ROTOR RUNOUT AND THICKNESS VARIATION
On vehicle rotor runout is the combination of the
individual runout of the hub face and the runout of
the rotor. (The hub and rotor runouts are separable).
To measure runout on the vehicle, remove the wheel
and reinstall the lug nuts tightening the rotor to the
hub. Mount Dial Indicator, Special Tool C-3339 with
Mounting Adaptor, Special Tool SP- 1910 on steering
arm. Dial indicator plunger should contact braking
surface of rotor approximately one inch from edge of
rotor (Fig. 10). Check lateral runout (both sides of
rotor) runout should not exceed 0.09 mm (0.0035
inch).
If runout is in excess of the specification, check
the lateral runout of the hub face. Before removing
rotor from hub, make a chalk mark across both the
rotor and one wheel stud on the high side of runout
so you’ll know exactly how the rotor and hub was
originally mounted (Fig. 11). Remove rotor from
hub.
VEHICLE ROAD TEST
5 - 14
BRAKES
300M
DIAGNOSIS AND TESTING (Continued)
Install Dial Indicator, Special Tool C-3339 and
Mounting Adaptor, Special Tool SP-1910 on steering
knuckle. Position stem so it contacts hub face near
outer diameter. Care must be taken to position stem
outside the stud circle but inside the chamfer on the
hub rim (Fig. 12). Clean hub surface before
checking.
Runout should not exceed 0.03 mm (0.0012 inch). If
runout exceeds this specification, hub must be
replaced. See Suspension Group 2. If hub runout
does not exceed this specification, install rotor on hub
with chalk marks two wheel studs apart (Fig. 13).
Tighten nuts in the proper sequence and torque to
specifications. Finally, check runout of rotor to see if
runout is now within specifications.
If runout is not within specifications. Install a new
rotor or reface rotor, being careful to remove as little
as possible from each side of rotor. Remove equal
amounts from each side of rotor. Do not reduce thick-
ness below minimum thickness cast into the un-ma-
chined surface of the rotor.
Thickness variation measurements of rotor should
be made in conjunction with runout. Measure thick-
ness of rotor at 12 equal points with a micrometer at
a radius approximately 25.4 mm (1 inch) from edge
of rotor (Fig. 14). If thickness measurements vary by
Fig. 10 Checking Rotor For Runout
Fig. 11 Marking Rotor and Wheel Stud
Fig. 12 Checking Hub for Runout
Fig. 13 Index Rotor And Wheel Stud
300M
BRAKES
5 - 15
DIAGNOSIS AND TESTING (Continued)
more than 0.013 mm (0.0005 inch) rotor should be
removed and resurfaced, or a new rotor installed. If
cracks or burned spots are evident, rotor must be
replaced.
Light scoring and/or wear is acceptable. If heavy
scoring or warping is evident, the rotor must be
machined or replaced. See Brake Rotor Machining in
the Service Procedures Section in this group of the
service manual. Refer to front or rear brake rotor in
the Removal And Installation section in this group of
the service manual for the required brake rotor
replacement procedure.
PROPORTIONING VALVE
PROPORTIONING VALVE TEST (WITH AND
WITHOUT ANTILOCK BRAKES)
CAUTION: Not all components use the same type
tubing flare. The tube leading into the proportioning
valve has an ISO flare, while the flex hose coming
out of the proportioning valve has a standard dou-
ble-inverted flare. Use the correct adapters when
installing gauges to test proportioning valves.
Both vehicles, with Antilock Brakes, and without
Antilock Brakes, have two proportioning valves. One
valve is connected to each rear flex hose. One propor-
tioning valve controls the right rear brake, and the
other proportioning valve controls the left rear brake.
On vehicles without ABS, if premature wheel skid
occurs on a hard brake application, it could be an
indication that a malfunction has occurred with one
of the two rear brake proportioning valves. Test the
valve that controls the side of the vehicle on which
the skid occurs.
On vehicles with ABS, if premature rear wheel
ABS cycling occurs on a hard brake application, it
could be an indication that a malfunction has
occurred with one of the two proportioning valves.
Since ABS cycles both rear brakes together, both
valves must be tested to isolate the suspect propor-
tioning valve.
(1) Raise the vehicle on jack stands or centered on
a hoist. See hoisting in the Lubrication and Mainte-
nance section of this manual.
(2) Clean any debris away from the suspect pro-
portioning valve, connections, and area.
(3) Remove the chassis brake tube (Fig. 15) from
the suspect proportioning valve.
(4) Remove the proportioning valve from the rear
flex hose which is held stationary by a bracket
mounted on the back side of the crossmember.
(5) Remove the retainer clip securing the rear flex
hose from its bracket (Fig. 15). This should be
done to allow the proportioning valve pressure
test fittings to be installed without bending the
chassis brake tube.
CAUTION:
Be sure the pressure test fittings being
installed into the proportioning valve, have the cor-
rect thread sizes for installation into the proportion-
ing valve and installation of the chassis brake
tubes.
(6) Correctly install Pressure Test Fittings, Special
Tool 6892–2 into the inlet port, and Special Tool
8187–2 into the outlet port, of the proportioning
valve (Fig. 16).
(7) Install the proportioning valve and the Pres-
sure Test Fittings, Special Tool 6892–2 and 8187–2,
as an assembly back into the chassis brake tube.
Fig. 14 Checking Rotor For Thickness
Fig. 15 Proportioning Valve
5 - 16
BRAKES
300M
DIAGNOSIS AND TESTING (Continued)
Connect Special Tool 6892–2 to the chassis brake
tube, and Special Tool 8187–2 to the brake flex hose.
(8) Install a Pressure Gauge, Special Tool C-4007-A
into each pressure test fitting (Fig. 17). Bleed any air
out of the system. This includes bleeding the air from
the hose between the pressure test fitting and pressure
gauge, which is done at the pressure gauge.
(9) With the aid of a helper, apply pressure to the
brake pedal until reading on proportioning valve
inlet gauge, is at the pressure shown on the following
chart. Then check the pressure reading on the pro-
portioning valve outlet gauge. If proportioning valve
outlet pressure does not agree with value shown on
the following chart, when inlet pressure shown on
chart is obtained, replace the proportioning valve. If
proportioning valve is within pressure specifications
do not replace proportioning valve.
(10) Remove the pressure gauges from the pres-
sure test fittings.
(11) Remove the proportioning valve and the Pres-
sure Test Fittings, Special Tool 6892–2, and 8187–2
from the chassis brake tube and rear flex hose.
Remove the pressure test fittings from the propor-
tioning valve (Fig. 16).
(12) Install the rear brake flex hose to its mount-
ing bracket using a new retainer clip.
(13) Install the proportioning valve to the rear
brake flex hose. Tighten to a torque of 17 N·m (145
in. lbs.).
(14) Install the chassis brake tube to the propor-
tioning valve (Fig. 15). Tighten the tube nut to a
torque of 17 N·m (145 in. lbs.).
(15) Bleed the affected brake line. See Bleeding
Brake System in the Service Adjustments section of
the manual for proper bleeding procedure.
(16) On vehicles with Antilock Brakes, repeat the
above steps for the other proportioning valve.
(17) If no problem is found with the proportioning
valves, check the rear wheel brake shoe linings for
contamination or for replacement brake shoes not
meeting OEM brake lining material specifications.
These conditions can also be a possible cause for a
premature rear wheel skid.
BRAKE FLUID CONTAMINATION
Indications of fluid contamination are swollen or
deteriorated rubber parts.
Swollen rubber parts indicate the presence of
petroleum in the brake fluid.
To test for contamination, put a small amount of
drained brake fluid in clear glass jar. If fluid sepa-
rates into layers, there is mineral oil or other fluid
contamination of the brake fluid.
PROPORTIONING VALVE APPLICATIONS AND PRESSURE SPECIFICATIONS
Sales
Code
Brake System Type
Split Point
Slope
Identification
Inlet
Pressure
Outlet
Pressure
BRT
15
9
Disc/Disc W/ABS
400 psi
0.43
Bar Code Label
1000 psi
525-600 psi
BNM
15
9
Disc/Disc W/ABS
And Traction Control
400 psi
0.43
Bar Code Label
1000 psi
525-600 psi
Fig. 16 Proportioning Valve With Fittings
Fig. 17 Pressure Gauges Installed
300M
BRAKES
5 - 17
DIAGNOSIS AND TESTING (Continued)
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст