Replacing A Brake Master Cylinder on a C3

When you hit the brake pedal at the end of Luskville's quarter mile you want to, rather you need to, feel some positive braking action happening big time.  You can have all the ponies in the world under the hood charging you ahead, but if you can't get stopped; you are in trouble.  The heart of our braking systems is the master cylinder and this article deals with the replacement of an old, tired one.

Note: This has been prepared as a guide only.  If you would like to offer any constructive criticism to improve the article - please feel free to contact me by clicking here...

- Loosen all the bolts, including the brake lines.

I loosen the brake lines first, make sure the line is not turning with the nut, a back and forth motion with the line wrench is the easiest.

- Remove the two nuts near the brake booster.

- Remove the old master cylinder. Make sure no fluid touches or drips anywhere, brake fluid will eat paint like nothing.

- Before installing new master cylinder. You will need to bench bleed it , this gets rid of the air inside of it.

- Attach the 2 plastic hoses to where the lines came off. If you have a vise, clamp the master cylinder. On it will be easier to bleed. Fill the reservoir about 3/4 full.

- Route the two hoses in the masters reservoir, get a big screwdriver and slowly pump the master cylinder.  Ensure the hoses stay in the reservoir and below the brake fluid.

- You should see small bubbles coming out of the hoses, keep doing this till there's no bubbles. If you keep getting bubbles, check to see if you small brakes lines are tight and under the brake fluid level.

- Once bled, install master cylinder. Cover and dry up any leftover fluid.  Be careful to hold the master upright.

- Re-install on the car. I start with the two nuts on the brake booster, just snug them for now.

- Remove the two bleeder hoses, install the brake lines and tighten them. Now tighten the nuts on the booster side.

- Now you need to bleed the lines on the car

BRAKE LINE BLEEDING

While bleeding the calipers I use a small plastic tube pushed on the bleeder screw  and it drains into a glass jar, just to make it less messy!

- Start at the wheel that is the farthest from the master, in this case the rear right wheel.

- This can be done with the wheel on but it is way easier with the wheels removed.

- Bleed the caliper until all the air is gone and there are "no bubbles".

- Bleeding the brakes is a two people job, you can do it with after market kits. I find it easier to have two people.

- When you pump the brake pedal don't go "nuts".  Just do a slow pump 3-4 times and then hold pressure on the pedal until your partner has opened the bleeder screw and released the pressure.

- When the pedal is on the floor or close to it let the other guy know. He will close the bleeder screw.  If you release the pedal before it will suck air in and will never get a good pedal.

- The next wheel to be done is the left rear,  Use the same procedure. Then do the right front and finally the left front wheels.

- Check the pedal for firmness and height; you may need to bleed them all over again.

- On cars with rear drum brakes, make sure the brakes are adjusted right.

- If you are happy with the brakes check and re-check for leaks while you buddy holds brake pressure.

- Re-install wheels and top up the master cylinder, start your car and check the pedal.

- Be sure to wipe up all the brake fluid.

ROAD TEST

- Slowly try to brake.  If all is good go for a road test.

- If the pedal feels spongy or you  are not happy with it , you may need to re-bleed the brakes.

- If all is good, keep an eye on your master cylinder for a few drives and make sure the fluid is not going down.