Yes - there is a "balance switch" that needs to be centered. it will
be tripped either to the front or the back. you need to try bleeding
the front brake with very light pressure, with someone watching the
light. As soon as the light goes out you need to shut the bleeder. If
that doesn't work, you need to bleed the rears the same way..
You don't need to take my word for it ----from
Use a test light by attaching a clip to a positive contact on the
vehicle and touch the point of the tester to the electrical connection
of the combination valve. If the the light does not come on, the valve
system is operating correctly and no further testing is required.
If the light does come on, this indicates that the pressure
differential valve is stuck in the front or rear position.
Bleed the brake system to determine if the front or rear lines are
blocked off. Set up one front wheel and one rear wheel for bleeding at
the same time. Crack both bleeder screws and gently pump the pedal a
The blocked side will trickle fluid out when the bleeder screw is
cracked and the pedal pressed. An unblocked line will squirt fluid out
The lines that are clear must be left open and the blocked lines
should have the bleeder screws tight to cause pressure to build up on
that side. Be sure to use the standard bleeding procedures to prevent
air from entering the system.
Slowly press the pedal with steady pressure a number of times until
the light goes out; this will center the differential valve. You may
also hear a pop come from the proportioning valve. This is the
metering valve returning to its equalized position. When the light
goes out, close the bleeder screw.
Still have light on. I noticed that when the brakes are pushed you can see
the fluid in the large chamber of master cylinder surging. Front cylinder
doesn't. Is that normal? The cover has 2 bellows but they don't fit the
front chamber. I looked at the old cover and it was flat all the way across
(no bellows). Could wrong cover have been put on new cylinder because it
doesn't seem like an airtight seal.
The bellows or lack tereof won't affect the action of the brakes - The
bellows is there to keep moisture-laden air from contacting the
hygroscopic brake fluid to keep it from absorbing water.
Have you "bench bled" the master? You need to get all the air out of
the master before attempting to bleed lines and center the valve.
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