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Clutch pedal goes to floor on first stroke after=20
a long rest, but works correctly otherwise. This=20
implies that the clutch slave cylinder piston has=20
retractred too far, requiring one pedal push to reset it to correst=
position.
The clutch slve cylinder should have a light=20
force compression spring inside. See here:=20
http://mgaguru.com/mgtech/hydraulics/ht107.htm
If that spring is missing the slave cyinder may=20
still work, but the piston might retract farther=20
than intended during a period of dormancy (long=20
drive without using the clutch). You might want=20
to open the slave cuinder to check on what's inside.
At 08:26 AM 11/8/2016 -0800, David Councill via Mgs wrote:
>....
>It is a bizarre problem. I was hoping someone=20
>might have had similar problems. Since my last=20
>email, I have made two 15 mile drives with the=20
>same very predictable issue. The master remains=20
>the primary suspect because the issue happened=20
>after replacing the master cylinder. The slave=20
>cylinder was an aftermarket replacement I put in=20
>about 4-5 years ago but the only thing I have=20
>done with it is to drain the brake fluid.
>
>A recap of this morning=92s typical drive =96 solid=20
>pedal through several gear shifts through town,=20
>started highway drive. During this highway part,=20
>I slightly pressed on the clutch pedal several=20
>times on the drive until resistance was felt to=20
>see what was happening After a couple of miles=20
>and coolant temp up to 160F, some slackness and=20
>as soon as I got to the next town where I work,=20
>I had almost full travel to the floor. But the=20
>one press of the pedal and it was back to almost=20
>normal, next time I shifted, the pedal was solid=20
>again and a routine drive to work through town.=20
>It should now be fine until I start the next highway drive.
>(if I was only doing city driving, I wouldn=92t be having any issues)
>
>The symptoms appear more to be like a seal issue=20
>as one to two presses of the pedal resolves the=20
>issue (until next time). However, I have seen=20
>hydraulic leaks before which are slight enough=20
>to allow air in/out but not leak fluid. The seal=20
>on the banjo is still the place of primary=20
>suspicion so I=92ll probably drain the master and=20
>then completely redo the connection to see if I=20
>can get a better seal. There is a slight wetness=20
>at that connection but not enough to make for=20
>even a minuscule drop of fluid. Also relevant, I=20
>installed a new Lockheed master cylinder as I=20
>mentioned. This is part LM13105, =93fits all years=20
>1962-1980=94. However, sources like Moss list=20
>separate clutch master cylinders for 62-67 and=20
>68-80. From what I can tell, they are identical=20
>with one small difference in how the master=20
>cylinder mounts to the pedal box (how the bolts=20
>line up) such that this new master cylinder does=20
>not sit up straight but has a slight tilt=20
>clockwise (5-10 degrees). That could be enough=20
>that the flare fitting might be damaged or=20
>slightly off on the banjo connection =96 or at=20
>least that is my primary theory at present. The=20
>only problem with that theory is that somehow=20
>air would be getting pulled in under no pressure=20
>or vacuum other than that generated by metal=20
>expansion. Hopefully, it is not the master=20
>cylinder and its seals at fault because that involves a lot more work.
>
>Still, I thought about asking the group about=20
>master cylinders before I started =96 re-sleeve=20
>versus new. The costs were about the same so I=20
>went with new. Maybe I should have tried one of=20
>those new plastic reservoir after-market units=20
>since this is my almost daily driver. For now, I=20
>will work with the banjo fitting but I may end=20
>up trying another master cylinder if that fails,=20
>perhaps take the one out of my 67 BGT which is=20
>slated for an engine overhaul due to worn rings=20
>and excessive oil consumption. Either way, I=92ll=20
>get this figured out sometime in the not too=20
>distant future and then I=92ll report back.
>
>David Councill
>64 MGB
>67 MGBGT
>72 MGB
>From: Mgs [mailto:mgs-bounces@autox.team.net] On Behalf Of PaulHunt73 via=
Mgs
>Sent: Tuesday, November 08, 2016 12:52 AM
>To: MG-MGB@yahoogroups.com; mgs@autox.team.net
>Cc: MG-MGB@yahoogroups.com
>Subject: Re: [Mgs] [MG-MGB] Clutch problems wuth thermal component
>
>"pedal goes almost to the floor with no resistance but enough to still=
work"
>
>Expand? If the biting point is very low when=20
>this happens, then either the pressure seal is=20
>not sealing when it should be, or there is air=20
>in the system. If the biting point remains=20
>'normal' then it's a purely mechanical issue,=20
>possibly pivots binding with heat expansion.
>
>If the banjo union at the master is wet then=20
>that does imply a leak, which may or may not let=20
>in air, and further tightening may not seal=20
>it. Also if it's wet it implies fluid loss,=20
>which should eventually become visible from the=20
>level in the master. But that may take some=20
>time, and it will be affected by fluid expansion=20
>and contraction with heat/cool cycles.
>
>If there is air getting in, then I can see that=20
>this becomes apparent on flooring the pedal,=20
>which will tend to push the air down while=20
>compressing it. But it will float to the top of=20
>the pipe while the pedal is down, then when the=20
>pedal is released it will be flushed out of the=20
>system into the reservoir. That is one of the=20
>many techniques that may be needed to get full=20
>travel of the clutch slave after working on the=20
>hydraulics. The effects of incomplete bleeding=20
>i.e. air remaining in the system would normally=20
>be apparent on every pedal operation.
>
>However that begs the question of how the air is=20
>getting in in the first place. The fluid is=20
>either under no pressure at all (pedal=20
>released), or under pressure (anywhere beyond=20
>where the master piston seal closes off the=20
>bypass hole to the reservoir). If air was=20
>getting with the pedal released then it would be=20
>apparent on the first operation no matter what=20
>the temperature was, and more than once on each=20
>drive. And the pressure while the pedal was=20
>anywhere in its disengagement portion should=20
>stop air getting in, even on the upwards stroke,=20
>as it is the cover plate that is pushing back on=20
>the slave piston and hence the fluid, which is=20
>the main factor in returning the master piston and hence the pedal.
>
>The other possibility is that something is=20
>causing the slave piston to be pushed back into=20
>the cylinder while you are driving, pushing=20
>fluid that should normally be in the system back=20
>into the reservoir, and creating lost-motion at=20
>the release arm. This has to be taken up before=20
>you can start to disengage the clutch, so=20
>reducing pedal back-pressure and lowering the biting point.
>
>But I can't really see how that could suddenly=20
>start happening with the new master, so the new=20
>master (subject to getting a proper seal on the=20
>banjo) has to be the prime suspect.
>
>PaulH.
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<html>
<body>
Clutch pedal goes to floor on first stroke after a long rest, but works
correctly otherwise. This implies that the clutch slave cylinder
piston has retractred too far, requiring one pedal push to reset it to
correst position.<br><br>
The clutch slve cylinder should have a light force compression spring
inside. See here:
<a href=3D"http://mgaguru.com/mgtech/hydraulics/ht107.htm"; eudora=3D"autourl=
">
http://mgaguru.com/mgtech/hydraulics/ht107.htm<br><br>
</a>If that spring is missing the slave cyinder may still work, but the
piston might retract farther than intended during a period of dormancy
(long drive without using the clutch). You might want to open the
slave cuinder to check on what's inside.<br><br>
<br>
At 08:26 AM 11/8/2016 -0800, David Councill via Mgs wrote:<br>
<blockquote type=3Dcite class=3Dcite cite=3D"">....<br>
It is a bizarre problem. I was hoping someone might have had similar
problems. Since my last email, I have made two 15 mile drives with the
same very predictable issue. The master remains the primary suspect
because the issue happened after replacing the master cylinder. The slave
cylinder was an aftermarket replacement I put in about 4-5 years ago but
the only thing I have done with it is to drain the brake fluid.<br>
<br>
A recap of this morning=92s typical drive =96 solid pedal through several
gear shifts through town, started highway drive. During this highway
part, I slightly pressed on the clutch pedal several times on the drive
until resistance was felt to see what was happening After a couple of
miles and coolant temp up to 160F, some slackness and as soon as I got to
the next town where I work, I had almost full travel to the floor. But
the one press of the pedal and it was back to almost normal, next time I
shifted, the pedal was solid again and a routine drive to work through
town. It should now be fine until I start the next highway drive.<br>
(if I was only doing city driving, I wouldn=92t be having any issues)<br>
<br>
The symptoms appear more to be like a seal issue as one to two presses of
the pedal resolves the issue (until next time). However, I have seen
hydraulic leaks before which are slight enough to allow air in/out but
not leak fluid. The seal on the banjo is still the place of primary
suspicion so I=92ll probably drain the master and then completely redo the
connection to see if I can get a better seal. There is a slight wetness
at that connection but not enough to make for even a minuscule drop of
fluid. Also relevant, I installed a new Lockheed master cylinder as I
mentioned. This is part LM13105, =93fits all years 1962-1980=94. However,
sources like Moss list separate clutch master cylinders for 62-67 and
68-80. From what I can tell, they are identical with one small difference
in how the master cylinder mounts to the pedal box (how the bolts line
up) such that this new master cylinder does not sit up straight but has a
slight tilt clockwise (5-10 degrees). That could be enough that the flare
fitting might be damaged or slightly off on the banjo connection =96 or at
least that is my primary theory at present. The only problem with that
theory is that somehow air would be getting pulled in under no pressure
or vacuum other than that generated by metal expansion. Hopefully, it is
not the master cylinder and its seals at fault because that involves a
lot more work.<br>
<br>
Still, I thought about asking the group about master cylinders before I
started =96 re-sleeve versus new. The costs were about the same so I went
with new. Maybe I should have tried one of those new plastic reservoir
after-market units since this is my almost daily driver. For now, I will
work with the banjo fitting but I may end up trying another master
cylinder if that fails, perhaps take the one out of my 67 BGT which is
slated for an engine overhaul due to worn rings and excessive oil
consumption. Either way, I=92ll get this figured out sometime in the not
too distant future and then I=92ll report back.<br>
<br>
David Councill<br>
64 MGB<br>
67 MGBGT<br>
72 MGB</blockquote><br><br>
<blockquote type=3Dcite class=3Dcite cite=3D""><b>From:</b> Mgs
[<a href=3D"mailto:mgs-bounces@autox.team.net"; eudora=3D"autourl">
mailto:mgs-bounces@autox.team.net</a>] <b>On Behalf Of </b>PaulHunt73 via
Mgs<br>
<b>Sent:</b> Tuesday, November 08, 2016 12:52 AM<br>
<b>To:</b> MG-MGB@yahoogroups.com; mgs@autox.team.net<br>
<b>Cc:</b> MG-MGB@yahoogroups.com<br>
<b>Subject:</b> Re: [Mgs] [MG-MGB] Clutch problems wuth thermal
component<br>
<br>
"pedal goes almost to the floor with no resistance but enough to
still work"<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.<br>
<br>
PaulH.</blockquote></body>
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