Brake Bleeding





Special hints on bleeding the brakes on your car.

For a description of the basic procedure, you would be best off checking your shop manual. However, if you are having problems with bleeding your brakes, the below hints may help!

Hints on Brake Bleeding.

Getting no fluid out of a bleed nipple

This is going to sound really simple, but is the master cylinder topped off with fluid? It is is surprisingly easy to forget to do this!

If you have fluid in the master cylinder, try removing the bleed nipple entirely and see if you get flow under pedal pressure.
o Case 1. Fluid squirts from line: You have a blocked or corroded bleed nipple, which will need to be cleaned out with an awl or similar pointy tool, or replaced.
o Case 2. Still no fluid: Unscrew the hose at the car side so it doesn't twist or kink, and see if you get a stream of fluid under pedal pressure. When testing, have a wadded rag over the end of the line to catch the fluid - the pressure is great enough to spray the other side of the garage, get in your eye or on your paint, etc. Also, press on the pedal about a dozen times when doing this. If the fluid all drained out of the system before you started bleeding the brakes, (if you overhauled some part of the brake system) it can take a surprisingly long time to pump fluid throughout the system.

Soft brakes even after bleeding

You probably still have air in the system somewhere. If you have had
parts of the brake system disconnected, ensure that the bleed nipples
for the wheel cylinders and front calipers are at the top, so that the
air can all escape during the bleeding process. (The air bubbles rise
to the top.)

* Front or Rear brakes bled, but no luck at other end

Your Pressure Differential Warning Actuator (PDWA) may be tripped.
This would close off either the front or back hydraulic circuit and
leave the other functional. It's easy to trip this when bleeding the
brakes. If this is your problem, the brake warning light will glow
brightly when the ignition is turned on. (Unless of course your brake
warning light switch or bulb is not working...)

If the PDWA is tripped, the shuttle in the PDWA can be re-centered by
the following procedure:
o Open a bleed nipple on the brake system that does work.
o With the ignition switch on, observe the brake warning light.
Press on the brake pedal carefully and watch the light. It and
the oil pressure light should dim as the switch centralizes. You
should also hear a click. Do not press too much or too fast, or
the switch goes past center. Just keep repeating the proceedure
until it works, varying the wheel/brake circut until you figure
out which way the switch was on.
If the above absolutely does not work for you, the PDWA can be
mechanically recentered, but is more difficult, involving partial
disassembly of the PDWA unit.

* You have tried all of the above, but still have no luck!

You may want to invest in a simple vacuum pump to bleed the brakes. One
such tool, available for about $20 at Walmart is the "Mityvac Vacuum Pump /
Brake Bleeding Kit." The pump is applied to a bleed nipple, and pulls fluid
through the system. This technique has the advantage that the master
cylinder does not require "priming" in order to get the bleeding process

In my experience, the vacuum pump does a good job and is a one-person
operation (with the exception of checking the results in the "conventional"
fashion). As always, your mileage may vary.