Lesson 6/Learning Event
c. When bleeding the treadle valve, use only low pressure, 10 to 12
psi, in the bleeder tank.
d. When bleeding the hydro-vac double stage control valve, rebleed the
highest bleeder screw three or four times to ensure complete air
a. Follow general bleeding procedures.
b. Clutch controls will always lose pressure and will not build up like
brake pedals do since pumping will not help.
Vertical Type Wheel Cylinders
a. Cylinders with an internal cross connecting line should be prefilled
Connect cylinders with the cross-line hand
tightened on the bench and prefill the cylinders.
pistons slightly will help to assure complete filling.
b. Hoses and lines should be pressure bled before connecting the wheel
cylinders. Rebleed units after installing.
Some vehicles have diagonal or vertical wheel cylinders which require surge
On such cylinders, the bleeder screw is not always the highest
point to allow air to escape, therefore, complete bleeding is difficult.
Surge bleeding will help:
a. Bleed each wheel with the pressure bleeder.
b. Open one bleeder screw at a time and have someone kick the brake
pedal vigorously a few times.
This will cause turbulence in the
cylinder forcing additional air out.
Before allowing the vehicle
operated, check the following:
Always check connections for leaks by applying heavy
pressure on the pedal or treadle.
If the system is
vacuum or air assisted, start the engine to create a
vacuum, or to build air pressure.