FLUSHING - TM-10-3930-607-150174

BRAKES

NOTE: The line is disconnected from the master

line to master cylinder fitting. Allow fluid to flow until the

cylinder to prevent flushing foreign particles from the

emitted fluid is clean and free of air bubbles, then

cylinder to the rest of the system, where they may lodge

tighten the fitting.

and later move into the wheel cylinder where serious

damage could result.

To help determine which

3. The master cylinder can be bled manually as

assembly is defective (during the flushing process metal

follows: Loosen the hydraulic fitting at master cylinder

particles may be flushed from the system), note the

until fluid oozes out. Depress the brake pedal. The

hose from which the particles come and check the

pedal will drop slowly toward the floor-board. Just

cylinder to which that hose is connected.

before the end of the pedal stroke, tighten the fitting.

Allow pedal to return to "off" position. Repeat procedure

3. If foreign particles or sludge had to be removed,

until, expelled fluid is clean and free of air bubbles.

fill master cylinder with alcohol and brush the inside of

the reservoir with a soft bristled brush. After brushing is

completed, operate brake pedal until reservoir is empty.

FLUSHING THE SYSTEM

NOTE: If foreign matter is abrasive, overhaul cylinder.

A. GENERAL

There are several reasons for flushing the system, some

4. When the reservoir is clean, connect the

of which are: existing fluid too viscous; operating

hydraulic line to the master cylinder and fill reservoir

conditions require fluid of different specifications;

with alcohol.

change in the brand of brake fluid (and the two are not

compatible); fluid is discolored or contaminated (dirt,

5. Operate pedal and keep adding alcohol until

metal particles, mineral oil, condensation, sludge).

clean alcohol flows from the bleeding hoses. If clean

fluid flows from one hose and not the other, close the

Use denatured alcohol as a cleaning agent. Do not

bleed valve connected to the hose from which the clean

employ flushing fluids containing mineral oil, kerosene,

fluid was expelled. Operate the pedal until clean fluid

carbon tetrachloride, etc., or use anti-freeze alcohol.

comes from the hose on the open valve.

Any of these in the hydraulic system will cause rubber

parts to swell and soften, endangering brake

6. When both bleeding hoses emit clean alcohol,

dependability. If any fluid of the foregoing type has

pump all the fluid out of the system.

entered the hydraulic system all rubber parts in the

system must be replaced, and metal parts thoroughly

cleansed.

7. Close the bleed valve closest to the master

cylinder. Fill fluid reservoir with specified brake fluid.

B. FLUSHING

Then operate brake pedal until 1/2 pint of brake fluid is

pumped from the system. Close the bleed valve

farthest from the master cylinder and open the other.

1. Attach a bleeder hose to the bleed valve (Fig.

Then pump another 1/2 pint of brake fluid from the

17) on each wheel cylinder, then open the valves. For

system.

valve location, refer to Bleeding. Place free end of hose

in a clear glass container.

NOTE: Be sure all of the fluid alcohol is pumped from

the system before starting to measure the brake fluid.

2. Unscrew master cylinder filler cap. Place a

drain pan under the master cylinder, then disconnect

8. Fill master cylinder to the specified level and

hydraulic line from the cylinder. Operate the brake

bleed the system. Make sure the filler cap is clean and

pedal until reservoir is empty. Inspect the reservoir.

vent holes open. Place a new gasket on the filler cap

Remove any foreign particles and sludge found in the

and screw cap into the master cylinder.

reservoir.

B-138