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"pedal goes almost to the floor with no resistance but enough to still =
work"
Expand? If the biting point is very low when this happens, then either =
the pressure seal is not sealing when it should be, or there is air in =
the system. If the biting point remains 'normal' then it's a purely =
mechanical issue, possibly pivots binding with heat expansion.
If the banjo union at the master is wet then that does imply a leak, =
which may or may not let in air, and further tightening may not seal it. =
Also if it's wet it implies fluid loss, which should eventually become =
visible from the level in the master. But that may take some time, and =
it will be affected by fluid expansion and contraction with heat/cool =
cycles.
If there is air getting in, then I can see that this becomes apparent on =
flooring the pedal, which will tend to push the air down while =
compressing it. But it will float to the top of the pipe while the =
pedal is down, then when the pedal is released it will be flushed out of =
the system into the reservoir. That is one of the many techniques that =
may be needed to get full travel of the clutch slave after working on =
the hydraulics. The effects of incomplete bleeding i.e. air remaining =
in the system would normally be apparent on every pedal operation.
However that begs the question of how the air is getting in in the first =
place. The fluid is either under no pressure at all (pedal released), =
or under pressure (anywhere beyond where the master piston seal closes =
off the bypass hole to the reservoir). If air was getting with the =
pedal released then it would be apparent on the first operation no =
matter what the temperature was, and more than once on each drive. And =
the pressure while the pedal was anywhere in its disengagement portion =
should stop air getting in, even on the upwards stroke, as it is the =
cover plate that is pushing back on the slave piston and hence the =
fluid, which is the main factor in returning the master piston and hence =
the pedal.
The other possibility is that something is causing the slave piston to =
be pushed back into the cylinder while you are driving, pushing fluid =
that should normally be in the system back into the reservoir, and =
creating lost-motion at the release arm. This has to be taken up before =
you can start to disengage the clutch, so reducing pedal back-pressure =
and lowering the biting point.
But I can't really see how that could suddenly start happening with the =
new master, so the new master (subject to getting a proper seal on the =
banjo) has to be the prime suspect.
PaulH.
----- Original Message -----=20
... Now I have a new problem - pedal motion is perfect until the car =
warms up and then most of the pedal resistance is lost briefly...
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<HTML><HEAD>
<META content=3D"text/html; charset=3Diso-8859-1" =
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<META name=3DGENERATOR content=3D"MSHTML 8.00.6001.23588">
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<DIV><FONT size=3D2>"</FONT><FONT size=3D3>pedal goes almost to the =
floor with no=20
resistance but enough to still work"</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Expand? If the biting point is very low =
when this=20
happens, then either the pressure seal is not sealing when it should be, =
or=20
there is air in the system. If the biting point remains 'normal' =
then it's=20
a purely mechanical issue, possibly pivots binding with heat=20
expansion.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>If the banjo union at the master is wet then that =
does imply a=20
leak, which may or may not let in air, and further tightening may not =
seal=20
it. Also if it's wet it implies fluid loss, which should =
eventually become=20
visible from the level in the master. But that may take some =
time,=20
and it will be affected by fluid expansion and contraction with =
heat/cool=20
cycles.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>If there is air getting in, then I can see that this =
becomes=20
apparent on flooring the pedal, which will tend to push the air down =
while=20
compressing it. But it will float to the top of the pipe while the =
pedal=20
is down, then when the pedal is released it will be flushed out of the =
system=20
into the reservoir. That is one of the many techniques that may be =
needed=20
to get full travel of the clutch slave after working on the=20
hydraulics. The effects of incomplete bleeding i.e. air=20
remaining in the system would normally be apparent on every pedal=20
operation.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>However that begs the question of how the air is =
getting in in=20
the first place. The fluid is either under no pressure at all =
(pedal=20
released), or under pressure (anywhere beyond where the master piston =
seal=20
closes off the bypass hole to the reservoir). If air was getting =
with the=20
pedal released then it would be apparent on the first operation no =
matter what=20
the temperature was, and more than once on each drive. And the =
pressure=20
while the pedal was anywhere in its disengagement portion should stop =
air=20
getting in, even on the upwards stroke, as it is the cover plate that is =
pushing=20
back on the slave piston and hence the fluid, which is the main factor =
in=20
returning the master piston and hence the pedal.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>The other possibility is that something is causing =
the slave=20
piston to be pushed back into the cylinder while you are driving, =
pushing fluid=20
that should normally be in the system back into the reservoir, and =
creating=20
lost-motion at the release arm. This has to be taken up before you =
can=20
start to disengage the clutch, so reducing pedal back-pressure and =
lowering the=20
biting point.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>But I can't really see how that could suddenly start =
happening=20
with the new master, so the new master (subject to getting a proper seal =
on the=20
banjo) has to be the prime suspect.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>PaulH.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: =
black">... Now=20
I have a new problem =96 pedal motion is perfect until the car warms =
up and then=20
most of the pedal resistance is lost =
briefly...</DIV></BLOCKQUOTE></BODY></HTML>
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