Cessna 150M - Brake Master Cylinders; Brake Master Cylinders Removal and Installation; Brake Master Cylinder Repair; Hydraulic Brake Lines

5-47. BRAKE MASTER CYLINDERS. The brake
master cylinders, located just forward of the pilot
rudder pedals, are actuated by applying pressure at
the top of the rudder pedals. A small reservoir is
incorporated into each master cylinder for the fluid
supply. When dual brakes are installed, mechani-
cal linkage permits the copilot pedals to operate the
master cylinders.
5 -48. BRAKE MASTER CYLINDER REMOVAL AND
INSTALLATION.
a. Remove bleeder screw at wheel brake assem-
bly and drain hydraulic fluid from brake cylinders.
b. Remove front seats and rudder bar shield for
access to the brake master cylinders.
c. Disconnect parking brake linkage and disconnect
brake master cylinders from rudder pedals.
d. Disconnect brake master cylinders at lower
attach points.
e. Disconnect hydraulic hose from brake master
cylinders and remove cylinders.
f. Plug or cap hydraulic fittings, hose and lines to
prevent entry of foreign matter.
g. Reverse the preceding steps to install brake
master cylinders, then fill and bleed brake system
in accordance with paragraph 5-58.
5-49.
BRAKE MASTER CYLINDER REPAIR. Fig-
ure 5-12 may be used as a guide during disassembly,
repair and reassembly of the brake master cylin-
ders. Repair is limited to installation of new parts,
cleaning, and adjustment. Use clean hydraulic fluid
(MIL-H-5606) as a lubricant during assembly of the
cylinders.
5-50. HYDRAULIC BRAKE LINES are rigid tubing,
except for flexible hose used at the brake master
cylinders and at the wheel brake cylinders on some
models. A separate line is used to connect each
brake master cylinder to its corresponding wheel
brake cylinder.
5-51. WHEEL BRAKE ASSEMBLIES. The wheel
brake assemblies use a disc which is attached to the
I
main wheel with the wheel thru-bolts or capscrews
and a floating brake assembly. (Refer to figure 5-3.)
5 -52. WHEEL BRAKES REMOVAL. Wheel brake
assemblies can be removed by disconnecting the brake
hose and removing the brake back plate. See figure
5-3 for brake assembly affected. The brake disc is
removed after the wheel is removed and disassembled.
To remove the torque plate, remove wheel and axle
or wheel only as outlined in applicable paragraphs in
this Section. Refer to figure 5 -3 for disassembly of
either wheel brake assembly.
5-53. WHEEL BRAKE INSPECTION AND REPAm.
a. Clean all parts except brake linings and O-rings
in dry cleaning solvent and dry thoroughly.
b. New O-rings are usually installed at each time
they are removed. If O-ring re-use is necessary,
they should be wiped with a clean cloth saturated in
hydraulic fluid and inspected for damage.
NOTE
Thorough cleaning.is important. Dirt
and chips are the greatest single cause
of malfunctions in the hydraulic brake
system.
c. Check brake lining for deterioration and maxi-
mum permissible wear. See paragraph 5-56.
d. Inspect brake cylinder bore for scoring. A
scored cylinder will leak or cause rapid a-ring wear.
Install new brake cylinder.
e. If the anchor bolts on the brake assembly are
nicked or gouged, they shall be sanded smooth to
prevent binding with the pressure plate or torque
plate. When new anchor bolts are to be installed,
press out old bolts and drive bolts in with a soft
mallet.
f. Inspect wheel brake disc for a minimum thick-
ness of O. 190-inch. If brake disc is below minimum
thickness, install a new part.
5-54. WHEEL BRAKE REASSEMBLY. Lubricate
parts with clean hydraulic fluid and assemble compo-
nents with care to prevent damage to a-rings. Re-
fer to figure 5-3 during assembly of wheel brakes.
5-55. WHEEL BRAKE INSTALLATION. Place brake
assembly in position with pressure plate in place, then
install back plate. If torque plate was removed, in-
stall as the axle is installed or install on axle. If the
brake disc was removed from the wheel, install as
wheel is assembled.
5-56. CHECKING BRAKE LINING WEAR. New brake
lining should be installed when they are worn to a
minimum thickness of 3/32-inch. Visually compare a
3/32-inch strip of material held adjacent to each
lining to measure the thickness of the lining. The
shank end of correct size drill bit makes an excellent
tool for checking minimum thickness of the brake
linings.
5-57. BRAKE LINING INSTALLATION. (See figure
5-3. )
a. Remove bolts securing back plate and remove
back plate.
b. Pull the brake cylinder out of torque plate and
slide pressure plate off anchor bolts.
c. Place back plate on a table with lining side down
flat. Center a 9/64-inch (or slightly smaller) punch
in the rolled rivet, and hit the punch sharply with a
hammer. Punch out all rivets securing the linings
to the back plate and pressure plate in the same
manner.
NOTE
A rivet setting kit, Part No. R561, is available
from the Cessna Service Parts Center. This
kit consists of an anvil and punch.
d.
Clamp the flat side of the anvil in a vise.
Change 3 5-25