| The Porsche 944 uses a hydraulic clutch
engagement system - there are no cables involved with the actuation
of the clutch. When you press on the clutch, pressurized brake fluid
moves from the master cylinder through either a metal or rubber line
to the slave cylinder mounted on the transmission. This results in a
system that takes less physical effort to move.
Although this actually creates a more reliable clutch system, over
time, there can be a failure or break-down of the system if the
slave or master cylinder gets old and begins to leak or fail.
A spongy feel to the clutch pedal, grinding of gears when shifting,
long pedal travel, and hydraulic leaks under the car are all signs
that one or more components of the system have failed.
Replacement of both cylinders is a bit tricky due to their
locations. Letís begin with the clutch master cylinder. This is
located on the driverís side of the car, just to the right of the
brake master cylinder/brake booster. In order to remove it, youíll
first need to remove the spring clip that secures the pushrod from
the cylinder to the clutch pedal arm. Open the driverís side door
and wiggle yourself in up under the dash near the pedals. Youíll see
the pushrod from the cylinder going towards the clutch pedal arm.
Reach up and feel the end of the pushrod. There is a tension clip
that holds it on. Youíll need to use a small screwdriver to gently
pry the lip up then push the clip off. Unfortunately, itís one of
those things that you wonít be able to see very well due to the
location of the clutch safety switch bracket, but rest assured, the
clip is there (See Figures 1 and 2). Just take your time as it can
get a bit frustrating doing this all by feel.
In order to remove the clutch master cylinder, you will have to
remove some vacuum components and lines to allow access. Loosen the
hose clamps and carefully pull the diaphragm and vacuum lines off as
shown in Figure 3. Also remove the small vacuum line going to the
diaphragm. Also remove the two Philips screws holding the black
plastic cover onto the firewall just behind the vacuum diaphragm.
With the black plastic cover removed, separate the wiring harness
connector. (See Figure 4). This will allow some slack in the wiring
harness and help with access below. It also can help if you use a
small screwdriver to pry the wiring tie off the firewall (See
Figures 5 and 6).
Now follow the clutch hose back along the top edge of the firewall
and remove the 8mm nut holding the upper metal clutch hose to the
firewall. This will give some slack in the line and help to pull the
cylinder out (See Figure 7). Under all of these connections lies the
clutch master cylinder. Carefully move the vacuum lines, feed
lines and electrical connections aside and locate the two 13mm nuts
holding the cylinder to the firewall. These will be difficult to get
to due to the clearance under the hood, although you should be able
to reach them using a 13mm socket with a universal joint and
extension (See Figures 8 and 9). Once the nuts are removed,
carefully maneuver the cylinder up and out of the firewall enough to
loosen and remove the 12mm fitting for the clutch hose out of the
end of the cylinder. Then use a pair of vise grips to clamp off the
feed hose and cut the clamp holding the feed hose to the master
cylinder (See Figure 10).
Once out, lay the new master cylinder next to the old one. You will
need to transfer the metal block with the hole from the old push rod
onto the new one. This is the part that mounts to the clutch pedal
arm. Make a note of the number of threads on the old pushrod and set
up the block on the new push rod with the same number of threads
exposed (See Figure 11).
Now position the new clutch cylinder in place, feeding the pushrod
through the hole into the passenger compartment. Keep the cylinder
right ahead of the mounting studs and thread in the 12mm fitting for
the clutch pressure hose. Take caution to make sure you have it
threaded in correctly as they can easily cross-thread and strip.
Also use a new hose clamp to secure the clutch feed line to the new
clutch master cylinder. This replaces the crimp style clamp
originally on there (See Figures 12 and 13).
Now slide the cylinder back against the firewall and connect the
pushrod back up to the clutch pedal arm from inside the passenger
compartment. Now move back to the engine compartment. Youíll see
that there is no way to thread the two 13mm nuts on by hand. What I
like to do in situations like this is to place a dab of grease on
the inside of the socket, then place the nut in. This will prevent
the nut from falling out of the socket when you try to get it back
on the threads. Position the nuts onto the threads and tighten them
down. Wipe off any excess grease that may be on the nuts (See
Figures 14 and 15). Reconnect the hoses and place the vacuum
diaphragm back in place.
Now on to the slave cylinder. As a rule, you almost always want to
change the master and slave cylinder at the same time. It's
difficult to determine if either the master or slave goes bad when
the system fails, and you might end up having to do the job twice.
It's also a good idea to change the rubber fluid hose at the same
time you change out the master and slave cylinders. In our case, the
original fluid hose had cracked and was leaking where the rubber
portion met the metal fitting (See Figure 16 and 17).
Jack up the car so you can access the starter. Make sure you use
quality jack stands to secure the car up in the air and disconnect
the battery. This is important, as you will be removing the cables
going to the starter which are live. Due to the layout of the 944,
there are a few differences from other cars. For example, the engine
is located in the front of the car and the transmission is located
in the rear. This provides a good weight balance between the front
and rear of the car, resulting in an almost perfect weight
distribution. Due to this arrangement, the starter motor is located
on the clutch housing plate almost at the bottom of the car as
opposed to being mounted on the transmission. Youíll need to remove
the starter in order to access the slave cylinder which is directly
Remove the 8mm and 13mm nuts on the electrical connections to the
starter and set them out of the way. Now remove the two 19mm bolts
holding the starter to the clutch housing. One bolt will be easily
removed with a socket, however the other will require a open end
wrench to remove due to the space around the nut being tight. (See
With the starter removed, you will be able to
access the clutch slave cylinder. Remove the lower clutch hose
connection from the top of the cylinder using a 12mm flare nut
wrench, then remove the two 13mm bolts holding the slave cylinder to
the clutch housing. Make sure you have a drain pan handy to collect
the fluid that will drain out of the clutch hose (See Figure 19).
Now move up to the engine compartment and disconnect the old fluid
hose. You'll want to hold the clutch hose stationary with a 19mm
wrench while you loosen and remove the 12mm threaded fitting from
the top (See Figures 20 and 21). Lower the new fluid hose down from
the top of the engine and connect it to the metal fitting.
Now get back under the car and make sure that
the piston rod of the new slave cylinder seats correctly in the
small cup on the end of the throwout arm in the clutch housing. As
you fit the slave cylinder, you'll need to compress the piston to
get the screws to thread into the clutch housing. Just take your
time and make sure that the piston rod is seated. (See Figure 22).
The system now needs to be bled. I like to use
the Motive Products Power Bleeder (available from PelicanParts.com)
for this task. Attach the power bleeder to the top of the master
cylinder reservoir and pump up the pressure in the bleeder. NOTE: DO
NOT exceed 1 bar (14psi) doing so can damage the seals in the clutch
hydraulic system.. With the pressure bleeder set up, attach a hose
to the bleeder valve. Open the bleeder screw and let the system
bleed until there are no more air bubbles coming out while a helper
pumps the clutch pedal. It's also important to keep an eye on the
reservoir level. If the level drops below the clutch feed line,
you'll have to start bleeding all over again (See Figure 23). All
thatís left at this point is to re-attach the starter and battery
and set the car down and youíre good to go.
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