OK Chaps and Chapesses,
Now I really am looking for the wisdom of the list. Some of you may
remember the problems we were having on the J%*p, and it's blasted
clutch. Peter C suggested that we needed a plastic tip for the end of the
push rod on the slave cylinder, and we _did_ need it. The original must
have disappeared somehow, and the plastic tip is definately a necessity
......... BUT ..................
The darned thing STILL didn't work.
Let me capsulate what we have done, bear in mind that this whole thing
has
taken weeks of work to even get to the stage that it is at now......
Precisely nowhere!!!!
You may remember that my eldest daughter is not exactly a gentle soul,
and
we needed to replace the clutch assembly in the 1985 Jeep Cherokee Laredo,
4WD. The correct assembly was purchased, and duly installed. Dropping the
transmission was no mean feat, and putting the gearbox back into place was
not exactly like doing it on a Spridget, but we managed it, bled the
system, and never got a really hard pedal. We did leave the drive shaft
unconnected so that we could check that the clutch was operating. Needless
to say, it wasn't. The plastic tip that Peter told us about certainly
lengthened the throw of the slave cylinder push rod, but it still wasn't
going far enough to extend the throw out arm sufficiently to engage the
throw out bearing with the pressure plate. The obvious thought was that we
weren't getting all the air out of the line, and a call to Just Jeeps in
Austin informed us that we needed to bleed the slave 'off' the bell
housing. The bleed nipple is lower then the incoming line when the slave
is attached to the bell housing, and in order to bleed it of air it is
necessary to take it off. So, OK, we did that. We put the slave back on,
and ............. still not working. We decided that we should try to
ascertain if the throw out arm could actually be moved sufficiently to
actuate the clutch. Fisher fabricated a plate that we could bolt on in
place of the cylinder, with a long bolt between it and the mount, thereby
mechanically moving the throw out arm as the plate was bolted further
down. Eureka !!!!!! this worked - the drive shaft would turn when the
bolt actuated the throw out arm. We were making headway, we thought
................. OK, if the throw out arm and the rest of the assembly
would work mechanically, then the problem must be hydraulic, right?
............we shall see - read on.
So, given that the mechanism would work mechanically, we began to look,
in
more detail, at the hydraulic system. The master cylinder seemed to be in
good order, the slave cylinder was fairly new, but Fisher re-built it
anyway. The line between the two is comprised of two pieces. The one,
longer piece, has a section, about 10" long, of rubber hose. We blew air
through this and it did seem that it might be blocking upon occasion (the
dreaded breakdown of rubber hoses - creating a one way valve effect), so we
bought a replacement, confident that this would correct the situation. It
didn't. (Taking this line out and replacing it is not for the faint of
heart either - just a word to the wise). More bleeding of the system, and
still no luck.
Fisher decided that we should, perhaps, not rely on the rebuilt slave
cylinder, and that another new one might be in order. We purchased this
from the same local source (At great expense - even with a trade discount),
and duly fitted that, to no avail. More bleeding of the system, STILL not
working. By this time Fisher's hands are becoming quite sore with all this
bleeding off the bell housing.
The parts manager at the local supplier suggested that we might not
have
the pivot point of the throw out arm in place properly, just a suggestion!!
Something was obviously wrong, so, after much soul searching, we
decided
that we should drop the transmission again, just to be absolutely
sure. We'd already spent days and days on the hydraulic system, so perhaps
this was a possibility.
Whilst we had the transmission off, we removed and examined the throw
out
arm in great detail. There is a dished cup, cast into the inside of the
bell housing, where a ball bearing sits, held in place by the corresponding
dished cup on the throw out arm. The pressure of the throw out bearing,
with the pilot shaft going through it's center, keeps this somewhat 'hit
and miss' arrangement in place. The throw out arm is not bent, beyond it's
original angled shape, and is not cracked. Having gone through the whole
travail of re-fitting the transmission to the flywheel for the second time
we thought we should attempt the mechanical test again. We did, and it
did, so we were at least no further backwards than before.
After more telephone calls, and more e-mail messages, we decided that
we
should, perhaps, replace the master cylinder. It was the only thing on the
hydraulic system that we had not replaced. It did appear to be working,
but .............. by this time we were becoming desperate. A call to
Peter C and the master cylinder was on it's way. We fitted it, bled the
system, AGAIN, and ....... it made no difference whatsoever. Desperate
calls to John Black (resident transmission guru) and now everyone is
scratching their head.
If the problem was that the push rod in the slave cylinder was not
travelling far enough, then a longer rod should correct it,
right? Wrong. Fisher fabricated a new rod, but all which that would do
was push the piston back in the cylinder, and not move the throw out arm,
as it should do. John Black is of the opinion that, if we get a good hard
pedal, with the slave cylinder disconnected from the bell housing, which we
do, then the problem can't be hydraulic.
We do get a hard pedal with it off the bell housing, but when it is
reconnected, because we have to push the piston back into the slave
cylinder to get the whole thing back in place, the hard pedal goes away,
and the drive shaft still won't turn when the clutch pedal is
depressed. Did I say depressed ................. depressed, that doesn't
even come close to how we both feel at the moment.
Neither of us are fools, but we begin to feel like it. If the
hydraulic
system works when it is disconnected from the bell housing, and if the
throw out mechanism works mechanically, then why can't we make them work
together?
So, OK, we begin to look further. Now our attention is focused on the
pedal system. Closer inspection of the travel of the push rod in the
master cylinder (you can see the travel inwards if you get your head in
just the right position under the dashboard) shows that the rod isn't
actually moving very far at all. Examining the master cylinder that we
removed shows that the rod will travel quite far, much farther than the one
installed in the car. OK, why? Closer examination shows that the fire
wall is flexing, somewhat. Perhaps only about 1/4", but that might just be
enough. On the inside of the car there is a brace from the inside of the
car to the bolt on the master cylinder (through the fire wall) which is
closest to the driver's side, but not on the bolt which is closest to the
passenger side. There is also a crack in the fire wall. OK, so we need to
strengthen that, don't we. Fisher fabricates a plate that will bolt onto
two bolts that are protruding through the fire wall (they hold the brake
servo in place) that will also bolt onto the remaining bolt on the master
cylinder, thereby strengthening the mounting of the master cylinder, and
providing a secure base for the rod to push against. I won't bore you with
the details of the fixing of this plate, but it is now on the car, and does
what we wanted it to, but it STILL doesn't work.
At the moment, the pedal assembly is off the car. It does show some
signs
of wear, and the linkage is a little bent, Fisher is straightening it as I
type, but it isn't cracked, and all the welds are in tact. Perhaps, when
this is straightened, it will improve things, but honestly, my feeling is
that as it all worked before we changed the clutch assembly, it would
probably work now, if only we had the answer that is eluding us.
Late night telephone conversations with John Black; nuisance calls to
Robert Houston, Peter Caldwell & Robert at Just Jeeps; nightmares about
hydraulic systems; transatlantic telephone calls to my brother (the genius)
have all failed to solve this problem. Robert suggested that I send this
puzzle to the list to see what we could come up with. So, I earnestly
entreat you, does anyone have ANY ideas.
Elizabeth - not replacing clutches easily, in Comfort
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