Bleed the brakes
After the proportioning valve is installed, bleed
the air from the valve (as described in step 7 un-
der “Install the proportioning valve”), as well as
the motorhome’s brake system, before driving the
motorhome.
Failure to bleed the brakes will cause a reduction
in braking efficiency or a complete loss of brake
pressure, which may result in property damage,
personal injury or even death.
General information
You must bleed the brakes of every wheel that is
downstream from the brake tee (Figure 1) that was
used to install the proportioning valve.
Instructions for bleeding all of the brake lines are in-
cluded; however, it is not necessary to bleed the brakes
upstream from the brake tee, unless air was allowed
into the master cylinder by not replenishing lost brake
fluid.
We have included the generally-accepted methods
for bleeding brakes. However, applications vary. Before
bleeding the brakes, refer to the motorhome chassis
manufacturer for specific procedures.
CAUTION
Check the brake fluid level often while bleeding
the brakes. Add brake fluid as necessary to pre-
vent the brake fluid level from falling low enough
to allow air bubbles into the master cylinder. If air
is allowed into the brake system from the master
cylinder, all brakes, and all components connected
to the hydraulic brake system, must be bled.
Never use old brake fluid to fill the master cylin-
der, or to replace lost brake fluid. Old brake fluid
contains moisture and contaminants which may
damage the braking system or cause the brake fluid
to boil under certain conditions.
Failure to follow these instructions may result
in a complete loss of braking pressure, which may
cause property damage, personal injury or even
death.
Wear appropriate eye protection when work-
ing on the brake system. If brake fluid comes into
contact with your eyes, follow the manufacturer’s
instructions.
Failure to follow these instructions may cause
severe eye injury.
For ABS (anti-lock braking systems)…
The front of an ABS system can be bled in the
same manner as the traditional method described be-
low. However, the rear brakes must be bled with a pres-
surized bleeder system, or, the hydraulic accumulator
must be fully charged.
The hydraulic accumulator can be charged by start-
ing the engine.
Traditional method
This method requires:
•an assistant (to pump the brake pedal)
•a box-end wrench suitable for the vehicle’s bleed-
er screws. (An offset wrench allows the most move-
ment.)
•a supply of brake fluid
•a disposable container
•a length of clear plastic tubing to fit over the bleeder
screws. (The tubing must have an inner diameter which
will allow it to seal over the bleeder screws.)
1. First, remove the master cylinder reservoir cover
and fill the reservoir with brake fluid (if necessary) up
to the maximum marking. Reattach the cover.
Check the brake fluid level frequently while bleeding
the brakes.
2. If bleeding all brake lines, the sequence is deter-
mined by the location of the lines in relation to the mas-
ter cylinder — in general, always bleed the brake line
farthest from the master cylinder first, then the other
brake line in the same half of the circuit just bled:
If you know that the brake system is split front to
rear, as is the case with many rear wheel drive vehicles,
the sequence is as follows:
1. right rear
2. left rear
3. right front
4. left front
If you know that the brake system is split diagonally,
as is the case with many smaller front wheel drive
vehicles, the sequence is as follows:
1. right rear
2. left front
3. left rear
4. right front
3. Loosen the bleeder screw at the first wheel cylinder.
Remove the rubber cap (if present).
4. Position the box-end wrench over the bleeder
screw.
5. Place one end of the clear plastic tubing over the
nipple of the bleeder screw, and place the other end
of the tubing into the disposable container.
6. Instruct the assistant to “apply.” The assistant should
pump the brake pedal three times, then hold the pedal
down firmly and respond with “applied.”
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