RE: Clutch Bleeding 101 (Fwd)

["charles.slayman" <Charles.Slayman@domain.elided>]

Hi Robert,
	You can quit bleeding the clutch hydraulics.  If you are getting 1/2" travel
at the slave cylinder (~12mm), then the hydraulics are OK and the clutch
master is adjusted properly also.  And (TA DA!) your pedal shaft is not
bending at the weld (GOOD NEWS!)
	But if the clutch is not disengaging, there are two problems I have either
experienced or seen happen to others:

1)  CLUTCH DISC FRACTURING - One failure mechanism is for the disk hub to
start cracking.  As this happens, the disc goes out of planarity.  When you
disengage the clutch, it still drags slightly and causes the gears to crunch. 
One way to test this is to put the car in any gear.  Push the clutch in and
start it.  If the motor starts with causing the car to lurch, then there is
not enough drag to prevent the engine from starting.  But if you now try to
shift to another gear with the engine running and the gears crunch, then there
is enough drag to give the syncros a problem.  If this in indeed the problem,
it will get progressively worse until the hub shears from the friction disc
completely and you have no power.  Or as the hub and disc go out of planarity
even more, the hub springs start to clip the flywheel bolts.  This will sound
like the throwout bearing is going because it only makes a racket when you
depress the clutch.  With your foot off the clutch, the pressure plate keeps
everything planar.

2)  TRANSMISSION AND CLUTCH DISC SPLINES SEIZING - This is common for a car
that sits for a long time.  (I don't think this is the case for you.)  When
the splines get corroded or rusted, the disc cannot move freely back and forth
on the transmission input shaft.  When you disengage the pressure plate (which
is what the fork is really doing) and the disc cannot move freely back away
from the flywheel, then the disc will continue to be dragged by the flywheel. 
It's not solidly engaged (like when the disc and flywheel rusted together),
but it will drag on the flywheel because it cannot move completely away from
the flywheel.

	Either of these two problems are pretty serious.  If it is the disc starting
to fracture, you will have to remove the transmission.  If you do, have an
expert check the shape of the transmission bearings.  I had this problem
(actually sheared off my first disc completely after ~145K miles) and then
fractured a new disc (AP Racing heavy duty disc) after only ~25K miles because
the transmission input shaft bearing was shot.  I didn't recognize it.  The
slop and play in the input shaft put undue angular stress on the disc hub and
caused premature failure.
	If the problem is with the spline corrosion or light rust due to sitting for
a long time, then it should get better with time.  The more you use the
clutch, the more you will wear down the rust.  So don't pull the transmission
until you can rule out this problem.

Good Luck,
Charlie S
'89 Spider 

PS  I didn't mention anything about pressure plate fingers bending or throwout
bearing failure because these usually cause a hell of a racket (not just a
light noise as you engage and disengage the clutch).  And you made no mention
of this.

>----------------Begin Forwarded Message----------------<

Date: Sat, 22 Sep 2001 21:06:34 -0400
From: "Robert J Favali" <rob@domain.elided>
Subject: Clutch Bleeding 101
To: alfa@domain.elided

As a follow up to my heavy clutch dilemma I recently posted (many thanks to
the replies off Digest), I seem to be suffering from a severe case of
automotive ignorance ... or maybe incompetence.

I just completed replacing the clutch hose. Now I am struggling with
bleeding the system.
At first I did it the gravity method .... fill it up and let gravity push it
through. Then I moved to the clutch pumping method (thanks to my wife's
great legs) and saw clear fluid with no bubbles. I first put a speed bleeder
in but it could not eliminate >any< system air so I replaced it with the
original bleed screw (how does one install a speed bleeder in a wet system
and not get drowned with fluid pouring from the bleed hole?)

Then I checked clutch fork travel. According to the shop manual, the travel
on the slave cylinder cap / fork is 11-12mm. I measure about 1/2" at full
pedal press but cannot get the clutch to disengage the motor and allow me to
shift into reverse. So my thought is to bleed more to assure greater
cylinder travel to move the fork, etc.

I'll be damned if I can figure out why I cannot get all the air out.  I
suspect air in the system but after 4 pints of Castrol brake fluid, still no
clutch effect and grinding in reverse. I am ready for 6 pints of Guinness.
All joints are tight, no leaks, etc

What am I missing here?   This is not the first time I have bled a system
but it has me stumped.
As my wife said, "Go on-line and get some real answers!" Here I am.

Thoughts? Help?

TIA,
Rob Favali
Burlington VT
93 Spider Veloce (still has karma problem)

--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided
>----------------End Forwarded Message----------------<

--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided