'93 Cobra Master Cylinder install
1987-93(non-Cobra) Did you upgrade to SVO or Mark VII front rotors? Did you
get a rear disc set-up from a junk yard car or other car? Does your brake pedal now feel soggy? One answer is to install a '93 Cobra Master Cylinder. '93 Cobra master cylinders have a 2" bore as opposed to stock
Mustangs 1.75" bore. The stock master cylinder is good for stock bore calipers & wheel cylinders small volume requirement, but not for upgraded brake calipers and/or rear disc. The problem is that the '93 Cobra
master cylinder isn't a direct bolt on part. If you have looked at the proportioning valve, you can see that a few Ford engineers must have been smoking something really good to come up with this design. For some
reason, they designed '87-'93(non-Cobra) master cylinders with 3 outputs and the proportioning block controls fluid only between the front, right wheel and the rear brakes. The front, left wheel gets pressure straight
from the master cylinder. In this tech section, you'll see what modifications are necessary to install a '93 Cobra master cylinder in your '87-'93(non-Cobra) Mustang.
Necessary tools and supplies:
- Good, complete wrench set.
- 1/8" pipe thread tap. This will be for a modification of the proportioning valve.
- Tube flaring tool. You'll have to trim a brake line and flare the end.
- 1/8" pipe to female tube adapter. This is available in any good auto parts store.
- Brake fluid. Now would be a good time to upgrade to at least DOT 4 brake fluid.
Removal instructions:
1. Read directions, completely. Whenever starting work on anything, it's a good idea to understand what is ahead.
2. Unplug the brake fluid sensor.
3. Remove the 3 brake
lines to the master cylinder. The older the car, the more stubborn the lines will be. Make sure you have good tools that grab the sides well.
4. Remove the 2 nuts that secure the master cylinder to the
booster. You will now be able to remove the stock master cylinder.
5. Remove the 4 brake lines to the proportioning valve. These lines can be stubborn, too.
6. Remove the nut securing the
proportioning valve to the strut tower. The nut is accessible from the wheel well.
This completes the removal of the old master cylinder and proportioning valve. Now it's time to modify the proportioning valve and front, left brake line.
Proportioning Valve Modification instructions:
1. Remove the plug on the back of the proportioning valve. Make sure that you also remove the spring and valve behind the plug.
2. Remove the plug on the front of the proportioning valve. You have to do this so that you are
sure the block is clean before putting it back together. Make sure you also remove the spring washer, spring, and valve behind the plug.
3. Tap the back of the proportioning valve. Unfortunately, the adapter and the plug have different
threads. You'll need a tap for 1/8 pipe thread.
4. Clean the proportioning valve, thoroughly.
5. Install the adapter to the back of the proportioning valve. If you plan on installing an
aftermarket adjustable proportioning valve, do not reinstall the valve and spring found inside the block.
6. Reinstall the front plug. If you plan on installing an aftermarket adjustable proportioning valve,
do not reinstall the valve, spring, and spring washer found inside the block.
This completes modifications to the proportioning valve. Now its time to install the proportioning valve and modify the front, left brake line.
Proportioning Valve install / Front, Left Brake line Modification instructions:
1. Reinstall the proportioning valve. You need to do this so that you know how to bend the front, left brake line.
2. Install the 4 original brake lines to the proportioning valve.
3. Bend the brake line. If you use a tube bender carefully, you can bend the brake line the way you want it.
4. Cut excess brake line. The brake line will be longer than needed. But make sure you give
enough slack for error.
5. Flare the end of the tube. Dont forget to put the male tube connector before flaring the tube.
6. Install the brake line to the proportioning valve. This line goes to the new port created on the back of the proportioning valve.
This completes necessary modifications. Your car's proportioning valve should now look like this:
It's just a matter of reinstalling the master cylinder.
Master cylinder install instructions:
1. Reinstall the master cylinder to the booster.
2. Reinstall the 2 brake lines from the proportioning valve.
3. Plug the brake fluid sensor.
4. Bleed the brake system. Instructions to bleed a brake system can be found in many popular repair manuals.
There you have it. Now you can enjoy your new found braking ability without the soggy pedal feel.
