Tommorow the parts should be coming in. I need to know if there's a website out there that would have a walkthrough for the procedure. I also need to know if there's any special tools I'll need to do the job.

I'll need to know how to bleed the clutch, using the conventional two-person, pump-till-your-leg-is-dead method.

Thanks! <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />

 

Having just done this same repair a few weeks ago I would highly recommend getting a pressure bleeder, although I have heard of others using the two man method. Make sure you have a 13mm socket on a universal joint. You will need this to get to the two mounting bolts on the master. I used a 1/4" drive socket myself. Other than that the standard arsenal of tools should be enough. Be prepared to drop the starter and the very first thing to do is disconnect the battery. Good luck.

 

I don't think a pressure bleeder is necessary. I have one of those $5 Kragen one-man brake bleeder kit dealies. It's basically a hose, a speedbleeder type check valve, and a little reservoir with a magnet.

The important thing in my experience is to raise the rear of the car. This especially applies to 85/2+ cars with the funky route through the reservoir to the clutch MC hose.

YMMV! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

No pressure bleeder??? Have fun!

 

I just did this and did a write up on the procedure. Get the Motive bleeder!! It only took me about 15 minutes and the clutch was perfect. Here is the link to it:

<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=013373&p=" target="_blank">Clutch bleeding made easy</a>

 

I have both the vacuum (mighty-vac)and the pressure bleeder (Motive). I suppose either one will work, but the pressure bleeder is the way to go. The bleeding part took all but ten minutes. BTW a good time to bleed the brakes...then you don't have to worry about it for another two years.

 

I just replaced the master and slave in mine two days ago! 951sickness is right, disconnect the battery and remove the starter first. The slave, underneath the car and above the starter, is fairly easy to replace. The master, even though it's under the hood, is a lot harder to get to. I had to cut some wire ties and move (and remove) some vacuum lines and hoses to get to the master bolts. After that, I (attempted) to use the two-person method for bleeding the clutch. After two hours of that, still no clutch pressure! The clutch pedal stayed on the floor! I decided to follow the advice of many rennlist users and build a pressure bleeder (since nobody in my state had one!). I got all the needed parts from a local hardware store. It took about ten minutes to build and ten minutes to bleed! It works great! Definitely use a pressure bleeder!

Kelly

 

Go with the crowd on this one, get a pressure bleeder. Or... you could sit there with ketchup bottle and just **** yourself off!

 

I went up to get a vacuum bleeder at Autozone today, but unfortunately, because the store's only been open a week, they don't have any. They're going to hold one for me when they get shipment on Friday.

I'm still waiting for my damn parts to get here anyway. I HATE UPS! <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />

 

(I tried to post this this AM, but good ol' CP&L vetoed it by switching power right at 8:15 for line work...)

Search the archives for a thread that Ice Shark originated a few months ago on clutch repairs; I think there were two, you want the one with 'update' in the title. There are a _lot_ of good tips in there.

Socket w. knuckle & extension for the MC mounting bolts; put some sticky stuff (small piece of duc tape? I used 3M's old yellow weatherstrip & trim adhesive) in the socket, but have an extension magnet ready anyway...

A spring-finger tool worked well for R&R'ing the washers that go with these nuts.

Be very gentle removing the blue hose from the reservoir, if you remove it... the nipple on the reservoir isn't exactly robust (ask me how I know ).

Keep brake fluid off of paint at all costs. Consider some kind of impromptu fender cover.

As mentioned, disconnect teh battery ground cable _first_.

Jim, gone to dinner... <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />

 

I got a good write-up from James @ Pelican Parts complete with pictures that that I used this summer which should help. One thing I did differntly is that I did not pre-prime the cylinders like they did. I also used a Motive Powerbleeder which worked fantastic. One last think is that the flare fitting of the hard line going to the master cylider can be a PITA to get back threaded in. Just be patient and bend the hard line back in position so that the fitting goes perfectly stright into the female thread.

Have fun,

Skip

944 Clutch Master and Slave Cylinder Replacement

Like many modern vehicles, the 944 series Porsche uses a hydraulic
clutch actuation system. This is in contrast to a mechanical cable
operated system found on the 924 series and other earlier Porsches. The
reasons for using a hydraulic system as opposed to cable are smoother
operation with less peddle effort, and ease of maintenance with greater
reliability. I suspect that if you are reading this you are probably
questioning the notion of reliability though.

A hydraulic clutch operates much the same as the braking system on
every modern car. Through the miracle of fluid dynamics, force is
applied at one end of the system and a greater force is realized at the
opposite end. Specifically, when you depress the clutch peddle, a rod
pushes on a piston in the master cylinder which in turn transfers fluid
to the slave cylinder, pushing the slave piston in outward against a
lever which in turn disengages the clutch pressure plate. Because of the
forces required to accomplish such a task are so great, a special
high-density fluid must be used.

Like most automobiles, the 944 uses brake fluid to operate the
hydraulic clutch system. In fact, the 944 brake and clutch fluid draw
from the same source. Brake fluid is an obvious choice because of its
unique properties and its parity with the braking system. Brake fluid is
special because its fairly dense, resists boiling at high temperatures,
and is kind to the rubber seals used in these systems. The major
shortcoming of brake fluid is that it tends to absorb moisture, and with
it contamination. The two combined are what do the most to deteriorate
the system. When heated to boiling temperature, the oxygen in the
moisture expands creating air bubbles. The problem is that air bubbles
compress much more easily than anything in the system, rendering the
system useless. This is why regular fluid change intervals are
recommended, and increased intervals are recommended if you live in a
highly humid climate.

Like motor oil, not all brake fluids are created equal though. The
range of quality parallels prices from about one dollar per pint, to
about $80 per liter ( about $40/pt.). Good brake fluid usually costs
about $5-$7 per pint; the more expensive stuff is mostly used by
professional racing teams. The difference in quality can basically be
termed as "purity". The manufacture of brake fluid is monitored by DOT
and SAE (Department of Transportation and Society of Engineering
respectfully) and is measured by the fluids resistance to boiling: both
wet (contaminated) and dry (not contaminated) boiling points. Both these
figures should be printed on the container; if not, put it back on the
self and shop elsewhere. In my opinion: anybody who buys discount brake
fluid should be nominated for a Darwin Award. Darwin Awards are given to
participants in life who inadvertently perpetuate the stupid
circumstances of their own demise.

Just in case you were wondering, the more popular brands used by
performance minded individuals are : Castrol LMA, Ford Racing, ATE
(Alfred Teaves) 2000 or Super Blue, Motul 600, and Castrol SRF. Other
fluids sold by manufactures of brake components are usually pretty good
as well. Silicone brake fluid was once popular because it had a
relatively low moisture absorption rate but its shortcoming was that it
compresses more easily than standard brake fluid. This translated into
undesirable braking characteristics. Now silicone brake fluid is mostly
used in classic cars (which are seldom driven and rarely maintained).

Troubleshooting:

Since you ARE reading this I assume you suspect or at least expect your
car has some sort of clutch failure. The first symptom noticed by most
owners is when the clutch peddle sinks to the floor and fails to
return. This suspicion can be supported by viewing the action, (or
rather lack thereof), of the throwout fork through the inspection hole.
(Pic 2) Although there can be other reasons, such as a loose/broken
line, or broken mechanical part, the most common failure by far is a
defective clutch master or slave cylinder. It doesn’t really matter
which one because they are contaminated by the same fluid and should be
replaced as a set; failure of the other component will likely follow
soon. Further verification will be moisture or visible leaking around
the system master/slave cylinder (pic 3), or brake fluid on the drivers
side carpet. This should correspond with a reduced level in the brake
fluid reservoir.

The real culprit for a hydraulic failure is not exclusion of fluid from
the system, but rather inclusion of air. Even an air bubble smaller than
a pea can disable the clutch hydraulic system. Consider this: if there
is air in the system, it didn’t get there by accident. It probably
means it was vacuumed in past a leaking seal.

Another common, and sometimes overlooked, problem with 944 clutch
system is when the mounting area around master cylinder begins to
fracture. This is evidenced by excessive movement of the master cylinder
when the clutch peddle is depressed. In most cases, since the area so
cluttered, the actual fractures won’t be visible to the untrained eye,
except from inside the cabin. (pic 4)

Although it is mostly the earlier cars that are plagued with this
problem, I suspect we’ll see the same with the later cars as mileages
increase. In any event, just be forewarned and be prepared with a
contingency plan should you make this unwelcome discovery.

The Repair

Our textbook example guinea pig for this project is an ’84 944
afflicted will all the usual problems: a leaking master cylinder and
broken firewall.

In this case, since we knew the firewall was broken, we had to remove
the master cylinder first so the firewall could be repaired. Note that
we are only performing one step at a time for a reason. The reason being
that we want to retain as much fluid in the system as possible
throughout the project. Bleeding the system will be is a real bear if
the system should go dry.

The first step in this project to disconnect the battery before we
forget. Not only is this a good maintenance practice, it will be a must
to prevent DME damage during the welding, and electrical shock during
starter removal.

Before getting to the hart of the matter you will have to remove most
of the ancillary fuel injection junk from around the clutch master
cylinder. This only takes a couple minutes and makes you life allot
easier. Try to keep as much of the junk intact as possible so you don’t
have to worry about how it goes back together. (Pic 6)

<a href="http://boards.rennlist.com/upload/Hoses.jpg" target="_blank">http://boards.rennlist.com/upload/Hoses.jpg</a>

Now we can start by removing the blue feeder hose from the master
cylinder. The blue feeder hose is a special long-lasting silicone hose
with a cotton braided outer layer. This hose is fairly expensive (for
rubber hose) and can generally only be found at German car dealerships
or specialized parts retailers. Plan ahead to replace it unless is been
done recently. Even though this hose was designed to far outlast
conventional rubber hose, nothing lasts forever. At a minimum you will
likely destroy its cotton outer layer and replacement will give the
project a new and finished look.

Generally, if you plan to replace the hose, it doesn’t matter which end
you disconnect first. But you can save yourself a step by only
disconnecting the reservoir side. A small and shallow incision with a
razor blade will greatly assist in releasing the hose from its mooring.
In our case we had just replaced the hose the prior week when diagnosing
this problem so we removed the hose from the master cylinder end. In
this case it doesn’t matter if you pull out the plastic elbow from its
rubber socket since your new master cylinder will include these parts.
The hose was elevated and tucked over the top of the master cylinder to
prevent unnecessary spillage.

Now we remove the high pressure (hard) line fitting. The reason we do
this before removing the master cylinder retaining nuts is because brake
line fittings can be pretty stubborn if not maintained regularly (which
is most the time). Essential in this process is the use of a 12mm "line
wrench". A line wrench is characterized by its heavily shanked 6-point
box-end with an opening designed to (just) fit over the tubing (pic 5).
Use of anything other than this specially designed wrench will most
likely result in a damaged fitting, unnecessarily complicating this
task.

<a href="http://boards.rennlist.com/upload/Lineremoval.jpg" target="_blank">http://boards.rennlist.com/upload/Lineremoval.jpg</a>

We can now remove the master cylinder retaining nuts. This would
probably be pretty straight forward if not for the fact the nuts are in
a pretty cramped are area. The best tool we found for this is a 13mm
swivel head socket and a long extension. (pic 7)

Even though your new master cylinder comes with a new push-rod, these
parts seldom wear out or need replacement (or adjustment). For this
reason we chose to save some time and leave the old push-rod attached
to the clutch peddle while we replaced the master cylinder.

Before sending the car to the welder we removed the driver’s seat,
carpet, and loosened the steering wheel so the welder could have room to
work under dashboard. (pic 8). We also used a heat gun and screwdriver
to loosen the sealant from around the area to be welded. (pic 12)

Once the car was returned from the welder we were ready to install the
new master cylinder. But first we applied some paint the fresh welds to
protect them from rust (as least for a while). Por-15 or Eastwood Rust
Encapsulator is good for this task.

<a href="http://boards.rennlist.com/upload/Firewall.jpg" target="_blank">http://boards.rennlist.com/upload/Firewall.jpg</a>

Before we could install the master cylinder we had to "prime" it. This
involves filling the master cylinder to capacity while expelling as much
air as possible. This process is most effectively done by submerging the
master cylinder in fresh brake fluid and pumping the piston with the
pushrod till air bubbles cease to exist. But this method is messy and
wastes allot of fluid that can’t otherwise be reused. I prefer to use a
syringe.

Normally master and slave cylinders are shipped with caps in the
orifices to protect the innards from contamination prior to assembly. In
order to prime the master cylinder the caps must be removed, but keep
them handy as you will need them after the priming is done.

The priming is accomplished by holding the master cylinder with the
orifices on a level plain and the piston fully depressed with the push
rod. Have an assistant slowly fill one of the orifices while drawing out
the piston. Once the piston is fully drawn out, push it in again slowly
till a steady stream of fluid comes out the fitting end. Again, add more
brake fluid as you slowly draw the piston out. Repeat till the air is
expelled and replace the caps to reduce spillage while you work. (pic 9)

Now, because the caps were never designed to be leak proof, you will
need to work rather smartly (before the fluid leaks out). Place the
master cylinder into position, but don’t nut it down. Assuming the blue
feed is already attached to the reservoir, and the brake fluid reservoir
is topped off, remove the inlet cap (the one on top) from the master
cylinder. Allow the fluid to flow down the (blue) feeder hose as you
lower and install it to the master cylinder (top off brake fluid again).
Once secured you can remove the fitting cap from the (pressure) end of
the master cylinder and screw in the line fitting. These line fittings
tend to be somewhat temperamental and pretty much require a straight
shot in to get the threads started; then you should be able to snug up
the fitting by hand. Use you line wrench again to secure the fitting.
This is where allot of make the mistake of over tightening: just because
the fitting was a bear to get off doesn’t mean it needs to be installed
with the same veracity; 10-15 ft/lb should be enough. (Top off brake
fluid again).

Now, before you tighten down the master cylinder you will need an
assistant under the dashboard to guide the push rod into the master
cylinder boot as you do the final positioning. (pic 11). I personally
always keep a supply of metric stainless steel hardware on hand; so we
used stainless for the master cylinder retaining nuts to overt
difficulties with removal in the future. (pic 10)

All the work is from the top side of the car is now complete so the car
can be jacked up to replace the slave cylinder from the bottom. Don’t
forget to safely place the jack stands under sturdy suspension
components. In our case we only jacked up the left side of the car.

After removing the starter (make sure the battery is disconnected) and
tucking the wires out of the way, I use the 12 mm line wrench once again
to remove the feed line from the top of slave cylinder (pic 13). At this
point I only break the line loose to save myself the difficulty later.
The line was also rusted to the compression nut and I didn’t want to
risk breaking the line buy turning the nut against it. Watch for this on
all similar lines. Next I use a 13mm swivel socket to remove the two
mounting bolts. (pic 14) This can be done with a standard 13mm wrench,
but it takes a while since the bolts are pretty long.

Next I compress the push rod and wrap with high strength tape. The
reason I did this was to maintain pressure in the system and overt the
intrusion of air. (pic 15) Now its time to prepare the slave cylinder
for installation. This involves filling the slave cylinder with fluid
the same way we did with the master cylinder. Once the new slave
cylinder is ready we can quickly remove the old one and replace it with
the new one. At this point the compression nut only needs to be finger
tight.

In our case, since the compression nut was frozen, we ended up
unscrewing the slave cylinder from the nut, as opposed to unscrewing the
nut. We then used a silicone plug in the line temporarily while we freed
the nut with a little Liquid Wrench.

Once the feed line is connected we can reinstall the slave cylinder. We
now can install the two M6 (13mm) bolts, but only turn them in by a few
threads. Now crack open the bleeder screw and close it just tight to the
touch. This will allow sort of a self bleeding action as we tighten the
slave cylinder down. Once the Bolts are tightened to about 18 ft lbs you
can tighten the compression nut and the bleeder screw.

Now comes the hard part: bleeding the air out of the system. If all the
preceding was done correctly you will have little to no air remaining in
the system (such was our case). In any case you will need to bleed it
to be sure all the air is expelled.

Bleeding the clutch is similar to bleeding the brakes. You only need to
pump the clutch peddle 2-4 times, hold to the floor, and have your
helper crack open the bleeder screw momentarily. Once the bleeder is
closed you can repeat the process till all the air is expelled from the
system. Be sure to keep the brake fluid reservoir full at all times.

If you depress the clutch peddle and it fails to return that means you
have too much air in the system. This is a problem. People have tried
just about method under the sun to bleed these clutch systems but the
only thing that really works with consistent success is pressure
bleeding. Barring that you’ll need to find a way to at least get enough
fluid into the system that it can be pumped up with the clutch peddle.
Then you can bleed it normally.

After the system is properly bled you can reinstall the starter. The
only thing reaming to do is to adjust the clutch peddle free play. This
is done by climbing under the dashboard again and loosening the jamb nut
on the push rod. Turn the pushrod clockwise (to tighten) till it barely
contacts the master cylinder, then counter clockwise one or two turns
(doesn’t have to be exact). Check the operation of the clutch so that
the clutch begins to engage about an inch or better off the floor. Once
your happy with the adjustment you can tighten the jamb nut and take the
car for a well deserved spin around the county.


<a href="http://boards.rennlist.com/upload/Slaveremoval.jpg" target="_blank">http://boards.rennlist.com/upload/Slaveremoval.jpg</a>
<a href="http://boards.rennlist.com/upload/Slave.jpg" target="_blank">http://boards.rennlist.com/upload/Slave.jpg</a>