How to flush the slave
(The following procedure was
performed on a normal aspirated two wheel drive 993, the 993 twin turbo and the 4 wheel
drive model cars have a different hydraulic circuit which is separate from the brake's
hydraulic system, the procedures to bleed the slave cylinder maybe different)
The 993's clutch system is operated on a hydraulic system
that require routine fluid change. What makes this particular job difficult is that
the clutch slave cylinder's bleeder valve is located in front of the clutch slave cylinder
on top of the transmission. In order to keep your eyes on the fluid flow and operate
the wrench there is no way you can get to this part with both hands. Unless you
perform the process with another person's vision.
The procedure itself is simple, but this is definitely an
1 hour job.
(1). Jack the car up from the left rear jacking point, and
place jack stand under the front jack point and rear suspension pivot point. I did
not rest the car on the jack stands, they were there strictly for protection.
(2). Remove the left rear wheel.
(3). Remove the engine and transmission pan
(4). Reach up to the slave cylinder area from under the
car with your left hand while lying on the floor . Pull off the protective rubber
cap on the end of the bleeder valve, push on a 1/4" clear vinyl tubing onto the end
of the bleeder valve with the other end in some sort of disposable bottle for catching all
the old fluids.
(5). Hook up a power bleeder unit, or some sort of
pressure bleeder unit to the brake fluid reservoir. Prior to hooking up the unit make sure
you first remove the white cylinder inside the brake fluid reservoir.
(6). Get back underneath the left rear of the car,
and use a 7 mm open end wrench to unbolt the bleeder screw, since the limited maneuver
area this will require at least two movement of the wrench before the fluid will be
(7). It is always a good practice to change the to a
different fluid color fluid when doing a hydraulic system flush, this way you will know
when all the old fluids is completely flushed form the system when you notice the color
(8). Tighten the bleeder screw and install
the rubber cap and the rest of the stuff. Double check the brake reservoir level
after you have lowered the car.
Ray Calvo (pops) said that I am a RAT for not
mentioning in this web site that
I took this picture from the left rear wheel well opening of
the car, so here it is :)
In case if you
guys are interested in Ray Calvo's clutch slave bleeding experience please read
on.... "It is funny :)"
Killed three birds with one stone
Posted By: Ray Calvo <email@example.com>
Date: Saturday, 24 February 2001, at 9:19 a.m.
Well, kinda. After work yesterday, I
a) bled the clutch slave cylinder
b) tested my Power Bleeder
c) got some info off the Vertex front rotors
CLUTCH BLEED: printed Robin's procedure for a laugh
(read on), then went ahead with it. Generally followed Robin's directions, and agree
accessing the bleed screw is a royal PITA. Definitely a touchy-feely job, you can't see a
thing if your hand is up there trying to access the bleed screw. Tried both box and open
end wrench; think I opened the screw with a box and closed it with open-end. The screw is
very loose (well, mine was); I didn't even realize I had broken the screw loose till I
reached up and found I could move the screw with my fingers. The screw is a lousy design -
about 1" long, made up of about 1/4" of nipple end, 1/4" of hex wrench
fitting, and 1/2" of smaller pipe end. This setup is just asking for trouble like
being very difficult to position a wrench on the hex fittng and possibly overtightening
and snapping off the bleed screw.
AND ROBIN, YOU RAT!!!!!!! Your pretty picture on
your web site? While working on the car, could not figure out where you shot that picture.
Finally noticed it was shot from the left wheel well, looking in to the top of the tranny.
ONLY YOU HAD TAKEN OUT YOUR SPRING/SHOCK!!!!!!! Let people know, will you? Also, you had a
jack stand under the rear suspension mount? How you did this and still accessed the bleed
screw is beyond me; anyplace I put a stand got in my way when tried to get to the
POWER BLEEDER: Followed the directions with the
unit; will say it's nicely made and easily possible to get a airtight seal. Have to pump
like crazy to pressurize the unit, but works as intended. I only filled it with about 1/2
liter of fluid; made it easy to tilt the unit when wanted to stop filling the master
cylinder and vacate the fill tube and bring the reservoir level down to normal point. One
thing I will say: place the bleeder below the reservoir, and run the fluid supply line so
that the center is higher than the reservoir; makes it easier to vacate the supply line
and lower the reservoir level to the desired value at the end of the job.
Was all this worth it? I don't know. I pulled out about a
pint of fluid; the first portion had the look of used engine oil; black and totally
opaque. Quickly took on tint of clean fluid. Initial clutch trial and drive on crisp below
freezing night seemed to indicate clutch was like new. After about 1/2 hour, noticed some
clutch pedal hangup again. When pulled into the garage and worked the clutch with the
engine off, could definitely hear a loud squeak from the clutch, and the pedal felt notchy
when I was letting it up. So, might have more problems.
Here are some comments
from Jim Stover after his experience with the clutch slave
"James A. Stover" <firstname.lastname@example.org>
Subject:Brake fluid change
14 May 2001 10:49:22 -0400Robin:
As I mentioned some time ago, I was planning to replace
the brake fluid in my 95 993 and would send you some comments on the experience in case
they might be of general interest. I did it last weekend. Since my car has Option 224
(Active Brake Differential), I expected it to have the hydraulic pressure unit. I do not
see how ABD could work without an independent pressure source. Nevertheless, I could not
find the pressure unit or the accumulator tank in the car. So I just went ahead with the
normal procedure. The Motive pressure unit is a neat device; Ray's (?) idea of
making a "T" todo both cylinders at once is the way to go.
The only procedure I did that might be of general interest
was the clutch cylinder bleeding. I'm not sure if it contributes anything new over what
you have already covered on your web page, but below is a write up. Use it or not, any way
you wish. It is actually quite easy to do.
"Put the car up on jackstands to a HEIGHT that allows
you to easily maneuver your body underneath the car. Remove the left rear wheel. From
below the brake disk, using a light, you can see the clutch cylinder resting atop the
transmission in all its inaccessible glory. (See Robin's picture). Move around until you
can find a hand position that provides enough strength to pull the rubber cover off the
bleed nipple. Long, ape-like arms are an asset here. Maneuver a 7mm, 12-point box-end
wrench over the bleed bolt and on up against the cylinder, where it will hang freely. Work
your bleed tube over the nipple. Secure the bleed bottle out of the way so you won't kick
it over. Pressurize the hydraulic system following the instructions for your unit.
Maneuver yourself until you can get enough leverage on the wrench to loosen the bleed
bolt. The bleed tube will prevent the wrench from falling off. Watch the fluid going
through the clear bleed tube until it clears up. It is likely to be dark and grungy
looking initially. (Maybe this stuff should be bled out at least once a year). When the
exiting fluid is clear, snug the bleed bolt back closed and disconnect the system,
covering the nipple with the rubber cap"
Thanks, Robin, for all the help and advice you have