Brake Bleeding Procedure (Pressure); Brake System Leak Check - Piper SENECA II Service Manual

7-67. BRAKE BLEEDING PROCEDURE (PRESSURE).

a. Place a small clear plastic hose on the vent tube of the brake reservoir and place a second small
clear plastic hose on the bleeder fitting on one main landing gear. Place the open ends of these tubes
in a suitable container to collect the fluid overflow. Open the bleeder fitting one or two turns.
b. On the other main gear, slide the hose of the pressure unit over the bleeder fitting then open the
fitting one or two turns and pressure fill the brake system with MIL-PRF-5606H fluid.
c. With fluid continually flowing through the brake system, SLOWLY and together actuate the hand
brake and the toe brake pedal of the side being bled, several times, to purge the cylinders of air. On
dual brake installations, both right and left pedals must be actuated.
NOTE: By watching the fluid pass through the plastic hose at the fluid reservoir and the bleeder
fitting on the gear being bled, it can be determined whether any air is left in the system. If
air bubbles are evident, filling of the system shall be continued until all the air is out of the
system and a steady flow of fluid is obtained. Should the brake handle remain spongy, it
may be necessary to disconnect the bottom of the toe brake cylinders (next to the pedal)
and rotating the cylinder horizontally or even above horizontal and by use of the hand
brake alone, purge the air from the system.
d. Close the open bleeder fitting on the gear being bled. Close the open bleeder fitting to which the
pressure hose is attached; then close the pressure unit and remove the hoses from the bleeder
fittings. Check the brakes for proper pedal pressure. Replace the caps over the bleeder fittings.
NOTE: It may be necessary to remove any trapped air in the top of the wheel brake unit by
applying pressure to the system with the brake hand lever and slowly opening the bleeder
and release the hand lever.
e. Repeat this procedure, if necessary, on the other gear.
f. Drain excess fluid from the reservoir to fluid level line with a syringe.
g. Make sure all lines are secure and all fittings are tight. It should be noted that on older master
cylinders where the hole for the bleeder seat is tapered, the bleeder seat/fitting should be torqued at
75 to 90 inch-pounds. On the newer cylinders where there is a straight hole, torque the seat until the
O-ring seals the hole.

7-68. BRAKE SYSTEM LEAK CHECK.

a. Pull for a good firm hand brake and lock parking brake mechanism. Allow system to stand for
approximately 10 minutes: then, by gripping the parking brake handle, it should not be able to be
pulled aft further than the original set. Should the handle be able to be pulled toward the panel and
feel spongy, a leak is present at some point in the system. This leak may appear at any one of the
connections throughout the system or internally in the master brake cylinder or wheel brake
assemblies.
VII - LANDING GEAR AND BRAKE SYSTEM
PIPER SENECA II SERVICE MANUAL
1L18
01/01/09