Mityvac 06820 Diesel Compression Test Adapters - Manual (Page 19)

Page Number - 19
Form 822378
BRAKE LINE BLEEDING
Most low and soft pedal problems are
caused by air in the hydraulic lines,
which requires bleeding of the hydraulic
system. By using the pump with brake
bleeding accessories, the system can be
bled easily. Follow a wheel-to-wheel
sequence beginning with the wheel
closest to the master cylinder.
The Kit provides a simple, clean, and
quick method for bleeding the fluid lines in
the automotive brake system. The
creation of a vacuum in the reservoir jar
causes fluid to be drawn into the
reservoir jar. It should be noted that a tiny
stream of bubbles may be noticed in the
hose after all of the air is bled from the
lines. This is caused by air seeping
around the threads of the loosened
bleeder fitting and being drawn back
through the fitting by the suction of the
pump. Once the air is removed from
within the system, these tiny bubbles will
in no way jeopardize the bleeding
operation, since they are present only at
the fitting and do not enter the system. If
you wish, you can put grease or Teflon
tape around the threads of the fitting to
eliminate most of the bubbles.
The correct bleeding procedure follows:
1) Always make certain that the master
cylinder reservoir is filled and that a
supply of new, clean brake fluid of
the proper type is on hand to top off
the reservoir as the fluid level drops
during bleeding. Make sure that all the
bleeding fittings are clean prior to
beginning of the bleeding procedure.
2) Bleed the hydraulic system in the
following order:
a) Master cylinder bleeder fittings, if
equipped. (If installing a new or
rebuilt master cylinder, follow the
bench bleeding procedure which
follows.)
b) Bleeder fittings on the combination
valve, if equipped.
c ) Wheel cylinders and calipers in
succession beginning with the
wheel closest to the master
cylinder, and working to the
farthest one.
NOTE: Wheel balancing sequence varies
among manufacturers. Follow
manufacturer’s recommended
sequence (if known). Procedure
given in this article specifies to begin
bleeding wheel closet to master
cylinder. Regardless of sequence
used, always ensure all air is purged
from system.
3) Slip 1-1/2” of tubing between the
pump and the lid of reservoir jar at
port marked “TO PUMP” (FIGURE 15).
4) Attach 3-1/2” plastic hose to the
bottom of the cap (if not already
attached).
5) Affix at least a 12” piece of tubing to
the other reservoir jar port. Be certain
that the cover of the reservoir jar is
secure, but don’t overtighten.
6) Select the appropriate adapters. The
snap-over adapters (L-shaped) are
different sizes (small, medium, large).
They should fit snugly over the brake
bleeding fitting in order to seal
properly. The tapered adapters fit
inside the thru-hole of fitting and will
generally seal well when inserted
tightly with a pressing and twisting
motion. Attach adapter to reservoir
hose.
7) Place wrench on brake bleeding
fitting; attach adapter and pump
assembly and pump 10-15 times.
NOTE: If bubbles coming out of the
fitting are very small and even in size,
the air is probably coming from within
the system. It is not necessary to
eliminate these bubbles as they do not
affect brake operation. If desired,
these bubbles can generally be
eliminated by placing grease or Teflon
tape around the threads, to act as a
seal.
8) Open fitting slightly, only enough to
cause the fluid to enter jar (usually
1/4 to 1/2 turn).
9) After evacuating about 2” of fluid into
jar, tighten fitting. Keep master
cylinder full.
Repeat all previous steps on all
remaining wheels. If fluid is not drawn
into the jar after opening the fitting,
make certain the lid of the jar is tight.
You will not be able to produce the
necessary vacuum in the jar if the lid
does not fit securely. Occasionally
some dirt will get into the brake line, in
which case the pump may not be
totally effective. If this happens, have
someone touch the brake pedal once