[rebel-builders] Air bubble in the brake system
Posted: Sun Feb 19, 2012 6:19 pm
Hello, my two cents, when you bleed you do it from reservoir to bleeder (
you can also suck with vac pump on the bleeder ). On the pressure stroke
loosen the bleeder, let pressure out until oil/air stops coming from the
bleeder, then tighten the bleeder before releasing the handle or pedal. On
the release stroke the master cylinder will draw in oil from the
reservoir, if your bleeder is open during the up stroke it is possible to
draw in air through it. Before pushing on the pedal/handle again give it a
couple of seconds for the oil to be drawn into the system (watch the oil go
down in the reservoir, don't let it get empty or you have to start over ).
You have to open and close the bleeder on every stroke. You could let
gravity bleed the lines by leaving the bleeder(s) open and keeping the
reservoir full as it goes down. If your reservoir holds a half litre oil
bleed out this much at least and you will be sure there is no air left. As
long as your reservoir is the high point ( no loops or lines above it ) you
will not have any air left in any lines even if you have loops below it. If
after this you still have air in the lines it is possible you have a leak
somewhere on the suction side of your master cylinder or the cylinder itself
is defective. You can check this by deadheading the cylinder ( plug the
end ) and push the pedal/handle and see if it holds or completes a stroke.
Watch for leaks during this test. Before doing anything check all your
connections and that no lines go above the reservoir oil level
Hope this helps, Jose
----- Original Message -----
From: "Jay Yau" <jayyau28@hotmail.com>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, April 27, 2010 2:49 PM
Subject: [rebel-builders] Air bubble in the brake system
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you can also suck with vac pump on the bleeder ). On the pressure stroke
loosen the bleeder, let pressure out until oil/air stops coming from the
bleeder, then tighten the bleeder before releasing the handle or pedal. On
the release stroke the master cylinder will draw in oil from the
reservoir, if your bleeder is open during the up stroke it is possible to
draw in air through it. Before pushing on the pedal/handle again give it a
couple of seconds for the oil to be drawn into the system (watch the oil go
down in the reservoir, don't let it get empty or you have to start over ).
You have to open and close the bleeder on every stroke. You could let
gravity bleed the lines by leaving the bleeder(s) open and keeping the
reservoir full as it goes down. If your reservoir holds a half litre oil
bleed out this much at least and you will be sure there is no air left. As
long as your reservoir is the high point ( no loops or lines above it ) you
will not have any air left in any lines even if you have loops below it. If
after this you still have air in the lines it is possible you have a leak
somewhere on the suction side of your master cylinder or the cylinder itself
is defective. You can check this by deadheading the cylinder ( plug the
end ) and push the pedal/handle and see if it holds or completes a stroke.
Watch for leaks during this test. Before doing anything check all your
connections and that no lines go above the reservoir oil level
Hope this helps, Jose
----- Original Message -----
From: "Jay Yau" <jayyau28@hotmail.com>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, April 27, 2010 2:49 PM
Subject: [rebel-builders] Air bubble in the brake system
I bled the brake fluid twice, still found the same amount of air bubble in
the nylon tube (about 1.5 inches long of the air bubble).
I am pretty sure that I have pumped the fluid from the bottom up all the
way though with a pump I bought from aircraft spruce (pump the fluid into
the bleeder nipple and drain out of of reservor on the top). But after
settled down for while, still see air bubble in the tube.
Any one has similar problem?
Should I flush the fluid the other way around, from top to the bottom?
Jay
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