Here's some interesting info from Mityvac's web site on bleeding your brakes
using a vacuum pump. It helped with some common problems I've had with
bleeding brakes.
BRAKE BLEEDING - WHICH WHEEL FIRST?
Q: What is the proper sequence in which to bleed my brakes when using the
Mityvac(r) pump for vacuum brake bleeding?
A: When using the vacuum bleeding method to bleed brake systems on vehicles
which are rear wheel drive the sequence should start with the wheel closest
to the master cylinder and end with the wheel which is farthest from the
master cylinder. Example: LF wheel, RF wheel, LR wheel, RR wheel [This is
the opposite of normal "pump & release bleeding]
(However, when vacuum bleeding brake systems on vehicles which are front
wheel drive the sequence will change. These systems use a diagonal
configuration for safety purposes. On this system the sequence should start
with the wheel closest to the master cylinder as before, however the next
wheel in the sequence will be diagonally aligned with that wheel. Example:
LF wheel, RR wheel, RF wheel, LR wheel.)
Q: When I try to bleed my brake system using the Mityvac(r) pump I am
getting air bubbles in the line connected to the bleeder screw on the wheel
cylinder and little or no fluid is being collected in the reservoir jar. I
have tried several times to bleed my brakes without success. What is the
cause of this problem?
A: Usually this condition is caused by a small amount of air being pulled
between the threads of the bleeder screw and the body of the wheel cylinder
or caliper resulting in the appearance of several small bubbles in the line
connected to the bleeder screw. This can be corrected quickly and easily.
Before you begin to bleed the brake system we suggest that the bleeder
screws be removed at all four wheels. With the bleeder screws removed assure
all are clean and the passages of the bleeder screws are free of corrosion
or debris. (A small paper clip will work well.) Next, be sure that all brake
fluid, penatrating oil, and or grease is removed from the bleeder screw.
(Brake cleaning solvent does an excellent job.) Apply a 2 to 3 inch piece of
Teflon(r) tape to the threaded area of the bleeder screw only. Wrap the tape
in the opposite direction of the rotation of the threads. This will prevent
any sepage of air from around the threads. Install each bleeder screw back
into the corresponding caliper or wheel cylinder and lightly seat the
bleeder screw. Now you are ready to begin bleeding the brake system! This
may seem like quite a bit of work in the beginning, but, once you get
started it should only take minutes to complete. In fact, the procedure
outlined above is an important step when bleeding brake systems regardless
of the method used. It is critical to be sure that each component in the
brake system is in proper working order to assure a long lasting repair.
Remember, the brake system is the most important system in your vehicle. If
the brake system fails to perform correctly, the results could be
disastrous. [Also, this makes it a heck of a lot easier to release the
screws -- no more snapped, rusted bleeders!]
-Dave
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