Model MA TOW Tractor. Manual - part 19

Chapter 3: Overhaul

Dec. 1995 Section 3-6 p. 1

VI .

REAR WHEEL DISC BRAKES (SERIAL NO'S 0128 AND UP)

SHOE AND LINING REPLACEMENT

Inspect the brake linings any time that the wheels are removed. Check both ends of the outboard
shoe by looking in at each end of the caliper. These are the points at which the highest rate of
wear normally occurs. However, at the same time, check the lining thickness on the inboard
shoe to make sure that it has not worn prematurely. Look down through the inspection hole in the
top of the caliper to view the inboard shoe. Whenever the thickness of any lining is worn to the
approximate thickness of the metal shoe, all shoe and lining assemblies on the axle set should
be replaced.

Removal:

(a)

Remove two thirds (2/3) of the total brake fluid from the master cylinder reservoir.

This step is taken to avoid reservoir overflow when the caliper piston is pushed back
into its bore. Discard the brake fluid removed. Never reuse brake fluid.

(b)

Chock front wheels.

(c)

Raise the tractor and remove the rear wheels.

(d)

Push the piston back into its bore. This can be accomplished by using a “C” clamp.

(e)

Remove the two (2) mounting bolts which attach the caliper to the support bracket.

Lift the caliper off the rotor and position on the drive axle so that the brake hose
(Delco) or steel brake line (Kelsey-Hayes) will not support the weight of the caliper.

NOTE: It is not necessary to remove brake hose (Delco), but may be necessary to

remove steel brake line (Kelsey-Hayes) when relining disc brakes.

Removing Shoe and Linings, Sleeves and Bushings:

(a)

Delco Caliper

(1)

Remove the inboard shoe and support spring from piston. Dislodge the
outboard shoe and remove from caliper.

(2)

Remove the two sleeves from the inboard ears of the caliper and discard.
Remove the four rubber bushings from the grooves in each of the calipers ears
and discard.

(b)

Kelsey-Hayes Caliper

(1)

Slide inboard shoe and lining assembly out of the caliper support. Slide out-
board shoe and lining assembly out of caliper.

(2)

Remove outer bushings from calipers by pressing out of bore using a suitable
tool. Discard bushings.

Chapter 3: Overhaul

Dec. 1995 Section 3-6 p. 2

VI .

REAR WHEEL DISC BRAKES (SERIAL NO'S 0128 AND UP)

SHOE AND LINING REPLACEMENT

Removing shoe and linings. sleeves and bushings:

(b)

Kelsey-Hayes Caliper (cont)

(3)

Slide inner bushings (flanged) off guide pins and discard. Remove positioner
from guide and discard.

Cleaning and Inspection:

(a)

Examine piston area for fluid leaks by looking for excessive moisture around boot

area. Check dust boot for cuts, cracks or other damage which would affect its ability
to seal piston bore. If leaks are present or boot shows damage, caliper should be
overhauled. See specific Section.

(b)

If no defects are found, wipe clean the inside of the caliper including four ears where

bushings are installed. Wipe the outside surface of the dust boot clear of all dirt so
that when piston is pressed to bottom of bore, boot will fold back without coming out
of groove.

CAUTION: DO NOT USE COMPRESSED AIR TO CLEAN THE INSIDE OF THE
CALIPER SINCE THIS MAY CAUSE THE DUST BOOT TO BECOME UNSEATED.

(c)

Examine both sides of the rotor for scoring or rough finish. In normal use, a slight

ridge of rust may form on the edge of the disc. This ridge may be removed with
sandpaper. If additional rotor servicing is required, see specific Section.

Installing Shoe and Lining, Sleeves and Bushings:

(a)

Delco Caliper

(1)

Delco Silicone Lube No. 179-651, lubricate new sleeves, new rubber bushings,
and bushing grooves. Install rubber bushings in all four caliper ears.

CAUTION: IT IS ESSENTIAL THAT THE NEW SLEEVES AND RUBBER
BUSHINGS WHICH ARE INCLUDED IN EACH DELCO SHOE AND LINING
KIT BE USED AND THAT LUBRICATION INSTRUCTIONS BE FOLLOWED
IN ORDER TO INSURE PROPER FUNCTIONING OF THE SLIDING
CALIPER DESIGN.

(2)

Use Delco Tool, J-22835, to install the sleeve. Position the sleeves so that the
end toward the shoe and lining assembly is flush with the machined surface of
the ear.

(3)

Before installing inboard shoe, secure inboard shoe support spring, flat notch
type.

Chapter 3: Overhaul

Dec. 1995 Section 3-6 p. 3

(4)

Position the inboard shoe and lining in the caliper and push down until the
shoe lays flat against the piston.

NOTE: On inboard shoe and lining assemblies with wear sensor, there is a
specific left hand and right hand shoe. When installed properly, the wear
sensor will be toward rear of tractor.

(5)

Position the outboard shoe in the caliper with the ears at the top of the shoe
over the caliper ears and the tab at the bottom of the shoe engaged in the
caliper cut-out.

(b)

Kelsey-Hayes Caliper

NOTE: When installing new shoe and lining assemblies, it will be necessary to also

install new positioners, inner bushings and outer bushings.

(1)

Slowly and carefully push piston back into bore, if required.

(2)

Install new inner guide pin bushings in caliper with flanged end on inboard
side.

(3)

Compress flanges of outboard bushing in fingers and work into position in hole
from outboard side of caliper.

(4)

Slide new shoe and lining assemblies into position in caliper support and
caliper being sure that metal portion of shoe is fully in recess of caliper and
caliper support.

Installing Caliper Assembly:

(a)

Delco Caliper

(1)

Position caliper over rotor and line up holes in caliper ears with holes in the
mounting bracket. Make sure the brake hose is not twisted or kinked. Wipe all
dirt and corrosion from the caliper mounting bolts and lubricate both ends of
bolts with Delco Silicone Lube No. 179-651.

CAUTION: DO NOT USE ABRASIVES ON THE BOLTS SINCE THIS MAY
DAMAGE THE PLATING. IF THE BOLTS ARE DAMAGED OR CORRODED,
THEY SHOULD BE REPLACED.

(2)

Start the bolts through the sleeves in the inboard caliper ears and mounting
bracket, making sure that the ends of the bolts pass under the retaining ears
on the inboard shoe. Push the bolts through to engage the bushings in the
outboard caliper ears, at the same time threading the bolts into the mounting
bracket. Tighten the bolts.

(3)

Pump the brake pedal to seat the linings against the rotors.

Chapter 3: Overhaul

Dec. 1995 Section 3-6 p. 4

VI .

REAR WHEEL DISC BRAKES (SERIAL NO'S 0128 AND UP)

SHOE AND LINING REPLACEMENT

5. Installing Caliper Assembly:

(a)

Delco Caliper (cont)

(4)

Using a large pair of channel-lock pliers, clinch the outboard shoe by locating
pliers on top of upper ear. Be sure to clinch both ends of the shoe.

NOTE: Alter clinching, there should be no radial clearance between the shoe
and caliper housing. If radial clearance exists, repeat clinching procedure.

(5)

Install rear wheels and tighten lugnuts to one hundred (100) foot-pounds (135
N-m).

(6)

Add fresh hydraulic brake fluid to the master cylinder to bring the level up to
within 1/8" of the top. Before moving the vehicle, pump the brake pedal
several times to make sure it is firm. Do not move vehicle until a firm pedal is
obtained (bleeding may be necessary). Check master cylinder level again after
pumping the brake pedal.

(7)

Check-Out:

(a)

Check brake pedal for sponginess or hard pedal.

(b)

Drive tractor slowly and make several slow speed stops.

(c)

Check all brake fluid line fittings and caliper areas for fluid leakage.

(d)

Correct any discrepancies before returning tractor to normal service.

(b)

Kelsey-Hayes Caliper

(1)

Holding inboard shoe and lining assembly in position, carefully slide caliper
down into position in support bracket and over rotor. Align guide pin holes of
support bracket, inboard and outboard shoes.

(2)

Install new positioners over guide pins with open ends toward outside.

(3)

Install assembled guide pins from inboard side through bushing, caliper,
support bracket, inboard and outboard shoes and into outer bushings in caliper.

(4)

Press IN on end of guide pins and thread.

(5)

Check-Out

(a)

Check brake pedal for sponginess or hard pedal.

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