MANUAL BLEEDING
For
those of us who are not fortunate enough to have access to a power
bleeding tool, the manual brake bleeding procedure will quite adequately
remove air from the hydraulic system. The major difference between the
pressure and manual bleeding procedures is that the manual method takes
more time and will require help from an assistant. One person must
depress the brake pedal, while another opens and closes the bleeder
screws.
In addition to a length of clear neoprene bleeder hose, bleeder
wrenches and a clear bleeder bottle (old plastic jar or drink bottle
will suffice), bleeding late-model ABS systems may also require the use
of one or more relatively inexpensive combination valve pressure
bleeding tools (which are used to depress one or more valves in order to
allow component/system bleeding). To fully bleed the late model ABS
systems, a scan tool should also be used to run the system through
functional tests.
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Clean the top of the master cylinder, remove the cover and fill
the reservoirs with clean fluid. To prevent squirting fluid, and
possibly damaging painted surfaces, install the cover during the
procedure, but be sure to frequently check and top off the reservoirs
with fresh fluid.
CAUTION
Never reuse brake fluid which has been bled from the system.
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The master cylinder must be bled first if it is suspected to
contain air. If the master cylinder was removed and bench bled before
installation it must still be bled, but it should take less time and
effort. Bleed the master cylinder as follows:
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Position a container under the master cylinder to catch the brake fluid.
WARNING
Do not allow brake fluid to spill on or come in contact with the
vehicle's finish as it will remove the paint. In case of a spill,
immediately flush the area with water.
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Loosen the front brake line at the master cylinder and allow the fluid to flow from the front port.
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Have a friend depress the brake pedal slowly and hold (air and/or
fluid should be expelled from the loose fitting). Tighten the line, then
release the brake pedal and wait 15 seconds. Loosen the fitting and
repeat until all air is removed from the master cylinder bore.
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When finished, tighten the line fitting to 20 ft. lbs. (5 Nm).
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Repeat the sequence at the master cylinder rear pipe fitting.
During the bleeding procedure, make sure your assistant does NOT
release the brake pedal while a fitting is loosened or while a bleeder
screw is opening. Air will be drawn back into the system.
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Check and refill the master cylinder reservoir.
Remember, if the reservoir is allowed to empty of fluid during the
procedure, air will be drawn into the system and the bleeding procedure
must be restarted at the master cylinder assembly.
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On late model ABS equipped vehicles, perform the special ABS
procedures as described later in this section. On 4 wheel ABS systems
the Brake Pressure Modulator Valve (BPMV) must be bled (if it has been
replaced or if it is suspected to contain air) and on most Rear Wheel
Anti-Lock (RWAL) systems the combination valve must be held open. In
both cases, special combination valve depressor tools should be used
during bleeding and a scan tool must be used for ABS function tests.
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If a single line or fitting was the only hydraulic line
disconnected, then only the caliper(s) or wheel cylinder(s) affected by
that line must be bled. If the master cylinder required bleeding, then
all calipers and wheel cylinders must be bled in the proper sequence:
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Right rear
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Left rear
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Right front
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Left front
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Bleed the individual calipers or wheel cylinders as follows:
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Place a suitable wrench over the bleeder screw and attach a clear
plastic hose over the screw end. Be sure the hose is seated snugly on
the screw or you may be squirted with brake fluid.
Be very careful when bleeding wheel cylinders and brake calipers. The
bleeder screws often rust in position and may easily break off if
forced. Installing a new bleeder screw will often require removal of the
component and may include overhaul or replacement of the wheel
cylinder/caliper. To help prevent the possibility of breaking a bleeder
screw, spray it with some penetrating oil before attempting to loosen
it.
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Submerge the other end of the tube in a transparent container of clean brake fluid.
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Loosen the bleed screw, then have a friend apply the brake pedal
slowly and hold. Tighten the bleed screw to 62 inch lbs. (7 Nm), release
the brake pedal and wait 15 seconds. Repeat the sequence (including the
15 second pause) until all air is expelled from the caliper or
cylinder.
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Tighten the bleeder screw to 62 inch lbs. (7 Nm) when finished.
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Check the pedal for a hard feeling with the engine not running. If
the pedal is soft, repeat the bleeding procedure until a firm pedal is
obtained.
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If the brake warning light is on, depress the brake pedal firmly. If there is no air in the system, the light will go out.
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After bleeding, make sure that a firm pedal is achieved before attempting to move the vehicle.
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