I just replaced my master cylinder and the brake pedal is bland. Almost to the end to actually brake, where did I mess up?

 

Did you bleed the master cylinder before you installed it? If not there's your likely culprit. You pretty much -have- to bench bleed the master cylinder before installation. The other possibility is the rod for the power booster is in need of adjustment. There should be instructions on how to do that that came with your master cylinder, should it be required.

Once you get it working right, be careful you might end up with a new brake fluid leak you can't account for, due to the far superior pressure of a new unit vs that old tired one. (like I have going right now. It's not at the calipers, cylinder, or brake hoses. I am starting to think it blew out a pin hole in the steel lines, or one of the seals on the ABS Controller has given up the ghost)

Also make damn sure you bleed the brakes at each caliper.

If none of the above fixes it you're left with 3 possibles.
1 Defective Master Cylinder
2: Vacuum leak at the power booster or a broken power booster
3: the spongy old brake hoses are ballooning when you're pressing the brake pedal.

 

@ Aaron Keating

Dumb questions:
How do you bench bleed a master cylinder and do you have to plug the fittings or what to not have it leak out the fluid and get air back in it while you move it from the bench to back on the car?

 

I did bench bleed it. Maybe I did it incorrectly? Should I uninstall and try again?

 

When you get a master cylinder it should come with the bench bleeding kit. It's two little outlets you screw into the brake line holes, and 2 brake fluid resistant airline tubes which you run up to your reservoirs, from the outlet holes. With the reservoirs installed on the cylinder, top off the reservoirs with brake fluid. If you're rebuilding a master cylinder I know the really good kits also come with the bench bleeding kit. And you can sometimes find them in autopart stores.

You then ideally set the master cylinder in a table vice. (I like putting abit of wood on either side of the master cylinder to prevent putting too much pressure on the cylinder) But you can do it out in the yard laying in the grass (like I did with mine last time since I let a friend borrow my table vice) holding the cylinder to the ground with one strong hand and take a wooden dowel, sawed down broom handle whatever, and gently push the piston in the back of the master cylinder forward. Do it slowly, and only go in about 1/3 of the way in (check the instructions on your master cylinder to be sure, mine was 1/3) and then slowly let it out. Keep doing this until you no longer have air bubbles coming up in the reservoirs.

To be on the safe side, I then usually go 1/2 through the piston's travel, a couple of times and then a couple of times at full stroke.

If you leave the outlet fittings on and the hoses inside the reservoir it'll stay bled during installation, just remove them one at a time when you're screwing your brake lines back in. You'll still have to bleed the lines probably, but the cylinder itself will be good to go. Remember there's usually no such thing as a dumb question. It's only not asking that's dumb

It couldn't hurt. It'd knock out another variable. Hope that helps At least there aren't that many components to the car's Hydraulics. I'd also replace the vacuum line to the power booster to knock that out too. The vacuum hose isn't terribly expensive either from my understanding.

 

At this point, you have air in the system. Start with the farthest wheel and start bleeding at each caliper.

 

@ Aaron Keating

Thanks for taking the time to repond. Good information.