CONVERTING TO A HYDRAULIC CLUTCH
The first step in converting my clutch
to hydraulic was to locate a suitable donor vehicle. I chose an 84
Mazda pickup. Some things to consider in your conversion are the stroke
length on the slave cylinder, and the size and shape of the master cylinder.
My slave cylinder just barely has enough stroke length to operate the clutch,
one of the things that I miscalculated in my conversion. I hope to find
a cylinder with a longer stroke, and put it in at a later date.
After finding donor parts I
decided on the mounting location for the master cylinder. I located
my clutch pedal inside and measured its location using a hole in the firewall
that I could locate from the other side also. My clutch pedal had a hole
already in it for the push rod to connect to. I don't know if this is common
to all castings or if this was unique to mine. Make sure that where you
mount your master cylinder will give the right amount of throw for the
push rod. If you have to much throw you will probably ruin master cylinders,
and if you don't have enough throw you will not get the full travel from
your slave cylinder, and the clutch may not operate correctly.
Once I decided on the location I measured
from the engine side of the firewall and marked the spot. I drilled
through the firewall with a drill bit the size of the master cylinder.
I also drilled a hole above and below the main hole for the mounting studs.
If your master cylinder mounts in an area that is just sheet metal you
may want to build a mounting plate to spread out the pressure that the
cylinder is going to take from the pedal. After drilling the holes, I mounted
the master cylinder. I then measured the push rod length using the
push rod from the Mazda pickup. I found that the original push rod and
end could be used if the push rod had some threads cut off.
With the master cylinder done, I started
work on the slave cylinder. I had several ideas on how to mount the slave
cylinder, but due to time constraints I chose the quick and dirty method.
I mounted the slave cylinder so it operated the cross shaft. This mounting
method leaves one short connecting cable in the mechanism, but I have never
had to replace this cable anyway. I located the mounting point for the
slave cylinder, and manufactured a spacer to hold the cylinder out from
the frame so it would line up with the lever on the cross shaft. I mounted
the spacer to the frame, and bolted the slave cylinder to the spacer. Then
I measured the length of the push rod I would need. I manufactured
the push rod from oil hardening tool steel. I threaded one end to take
the original clevis from the cable and put a radius on the other end to
match the original push rod. I then hardened the rod, and cleaned the burnt
oil residue from the threads. I then used a buffing wheel and polished
the radius to a high polish to limit friction. I assembled the clevis and
push rod and connected them to the cross shaft.
The final item to connect is the hydraulic
line between the master cylinder and the slave cylinder. My slave
cylinder had a small length of flexible hose that allowed for movement
in it's original application. I left this in because if I took it out I
would have had to produce an adapter for the steel line to connect. I picked
up a length of line from my local auto parts store, make sure you get the
right line, as there are metric and American sizes. Try and get the line
as close to the right length as possible because you do not want to cut
it. If you have to cut it you will have to get the end reflared. The line
has to be double flared to match up. The flaring tools you buy at the auto
parts stores cannot put a double flare on the tube, so you will have to
go to a brake shop to get the flare redone.
Once you have the line connected fill
the master cylinder with fluid (whatever fluid was recommended for the
donor vehicle). Have someone help you bleed the system. The correct
procedure for bleeding is having one person in the cab and one under the
vehicle (make sure to chock the wheels). Run a clear vinyl tube from the
bleeder screw on the slave cylinder to a jar half full of clean fluid.
Have the person in the cab depress the clutch pedal completely and hold
it. After the pedal is depressed, open the bleeder screw until the pressure
is gone from the line. Close the bleeder screw, and then have the person
release the clutch pedal. Repeat this process until no more bubbles are
seen coming through the vinyl tube. Check the fluid level about every 4th
or 5th time to make sure you don't run out. If you run out it will suck
more air into the system and you will be starting over. Caution: never
reuse any fluid that you have bled out of the system. Dispose of the old
fluid in an appropriate manner.