I will be replacing the master cylinder tonight. Anything I should look out for? or tips and tricks?

86 F150, 4.9 inline 6, power brakes, 4wd.

thanks

 

Bench bleed the cylinder before you hook up the lines.

Kenny

 

what is bench bleeding and what does it actually do?

 

You buy a little plastic kit, it includes fittings that screw into the master cylinder and hoses. You run the hoses from the fittings back into the master. Then you use a phillips screwdriver to bleed the master cylinder before you install it.

Here is what I do to save a bunch of bleeding time. It works best if 2 people are involved:

1) Place a couple of layers of towels under the master cylinder
2) Dismount the old cylinder but leave the lines attached (you'll se why)
3) Mount the new cylinder
4) Bleed the new cylinder (bench bleed) to itself
5) take one of the bench bleed fittings out (start at the rear)
6) take the matching line off the old cylinder and get it in the new cylinder ASAP.
7) Now once you have the fitting in hand snug, have your buddy start to press the peddle really slowly while you wrench tighten the fitting (you should have it snug enough it takes less than 1 turn to tighten)
8) repeat with the front line
9) use some brake clean to clean up the excess fluid. It washes up easy.
10) With a little bit of luck you shouldn't need to bleed at each wheel. It wouldn't hurt if you did, but you should have bleed all the air from the line. this is the quick and dirty method and works great in emergencies!

You will lose some fluid down to the towel (you can put a catch can whatever down there), remove it after the brake clean step.

Does that help?
Kenny

 

so is it basically done to avoid bleeding the rest of the system or does it have to be done whenever the mc is changed?

 

You always pre bleed the master cylinder...If not you will be bleeding at the wheels for a long, long time.

The method I described will keep you from having to bleed at the wheels in a large majority of the cases. It also keeps leaks to a minimum. You can just do 1-6 and bleed at the wheels if you like. If you haven't bleed the brakes for a while, you might want to do this just to purge the lines of old fluid.

Kenny

 

i have had my brake lines open with no fluid for a couple months now...when i connect the brake lines to a new mc while still having the lines open to flush the lines out do i still have to bench bleed?

 

Always bench bleed the mc. It takes a lot of strokes to bleed the master of all its small air bubbble. Even though your lines are open, it will save you considerable time bleeding the system. Remember, start the wheel bleeding the farthest away from the mc then work your way forward (RR, LR, RF, LF).

Its not the only way it works, I am just trying to save you time and effort. Connect them dry and bleed away if you think it will work better, no big deal to me. You will burn a lot of brake fluid if you don't "pre-bleed/bench bleed" the master.

Kenny