cagotzmann

I have read many posts where people are having problems bleeding brakes after calipers / MC replacements etc. I have never had any problems but then I never did replace the master cylinder either.

Well it was my turn for this task.

Previously brakes are working great (track day use) Original MC and wildwood calipers all around. After track day found contaminated brake fluid in the front reservoir only. Thinking its something in the MC (oem original mc since 1978) the task was to replace the MC.


Now I understand the frustration people go through.

1978 corvette with Wilwood D8-4 calipers and a new wildwood 260-8556 Master Cylinder only change was the MC

ok the usual steps as everyone mentions.

1. Bench Bleed Master Cylinder
2. Pressure bleed / Pedal pump /gravity bleed all calipers etc.

Result no bubbles but also very soft brakes.

Next Bleed Master Cylinder again this time on the car but used the same procedure as bench bleeding. No bubbles

Result still very soft brakes.

Bleed all calipers again. Result very soft brakes.

Does this sound familiar ?

Ok Lets go to plan B I found a additional procedure that can be used if the usually steps don't work.

See my post https://www.corvetteforum.com/forums...-cylinder.html





As expected there is more air in the MC, but this procedure cured the problem. After the MC is cleared again. Back to great brakes.

As for Wilwood rear calipers you also need 1 additional step. REMOVE THE CALIPERS FROM THE ROTOR AND STAND ON END to bleed. They sit to level to get all the air out of the piston bores.

Wilwood MC 260-8556 you also need to verify the correct vacuum piston rod length. Using the factory rod length didn't allow the brakes to release 100% (brakes dragging). Changed length from 2.5" to 2.42" to allow the brakes to release.

I spent many hours confirming each step and the results.

So don't give up if you don't get the desired results first time.
This can be a very frustrating procedure, especially if you are not using factory parts.

Street Rat

Nice write up.
I've been through more than my share of brake fluid. Bleed bleed bleed.
Now that I have a reliable system down to bleed the brakes it can be done quickly.
I like using a brake switch centering tool also.
I will have to do the raise the rear bleed. That is some good info. These brakes work well when done right.

69Vett

jack up back of car to make the master cylinder level to bleed.
tap calipers (A lot)with rubber mallet to dislodge air bubbles stuck to the walls inside the calipers.