Soft brake pedal on '85 GT

[Dacotua]

Totally stock brake system. They were working fine with no changes made but now when I push on them the pedal goes to the floor pretty easy and the brakes barely work.
I checked the master cylinder and the fluid is not low. There are no visible leaks anywhere at the m/c, calipers, wheel cylinders, or any threaded fittings.
I have heard that bad seals inside the m/c can cause this. Anything else it could be based on these symptoms?
I've had bad boosters before but they made the pedal hard, not soft so I wouldn't think that's the problem.

Its not your brake booster.

It's either a bad master cylinder, bad wheel cylinder, bad caliper OR you got air in your system somehow.

If theres no fluid leaking at any corner, then its probably the master cylinder.

[Cooter]

you don't need two people... gravity is neato

[Josh.0]

bad mater cylinder as said I'v had 2 85's do the same thing.

Does your e brake work?

[Trick Pony]

bad mater cylinder as said I'v had 2 85's do the same thing.

Does your e brake work?

Yes, the e-brake works.

[Josh.0]

Yea, then it's prob the master cylinder.

[dumpycapri85]

Don't forget to bench bleed the master before you put it on or before you screw on the lines .

[bwild]

Yep its the master cylinder and gravity is your friend if no one can help you.

[LS1Goat]

Like already stated. That is almost always caused by a bad master cylinder or air in the system. Get a self using bleeder kit and hit all for corners.

[Trick Pony]

Don't forget to bench bleed the master before you put it on or before you screw on the lines .

It's been about 12 years since I had to do one on my '79 Pace Car but I did remember the bench bleeding part.

[03WhiteGT]

you don't need two people... gravity is neato

Agree.. Replaced the master cylinder in my 86 years ago. No matter how I bleed the brakes, I still had a soft pedal. Gravity bleed them for about an hour, then repeated the normal process and it worked like a champ.

[dumpycapri85]

It's been about 12 years since I had to do one on my '79 Pace Car but I did remember the bench bleeding part.

I just find it easyer to remove more air up top and make sure the master is full of fluid . That way you don't have to push any air bubbles all the way thru the system .

[Trick Pony]

I just find it easyer to remove more air up top and make sure the master is full of fluid . That way you don't have to push any air bubbles all the way thru the system .

Definitely a time saver. I noticed you Big Rooster guys seem to have a lot of 4-eyes. Want to help me do a carb conversion on my CFI '85?

[dumpycapri85]

Sure we can help you out . What is the build plan stocker or rocker ? I think we have about 18 79-86 foxes in the clan now looking for # 19 . LOL

[Trick Pony]

Sure we can help you out . What is the build plan stocker or rocker ? I think we have about 18 79-86 foxes in the clan now looking for # 19 . LOL

For now just a simple carb conversion. Weiand Stealth or RPM Air Gap intake with an Edelbrock or Holley carb. Later on heads and cam. Nothing too crazy, just a fun street cruiser. My vette and the other stang are the go fast toys.

[85whtgt]

Better stay away from dumpy, or you'll end up gettin greasy in his garage every weekend like the rest of us.