Fading brakes

[spoiledred94]

I have a very soft fading brake pedal. I've bled the rears twice and fronts once. There was a slight improvement but I have to pump once and then even though its stiff it fades all the way to the floor very slowly. I've been all around and in both the front and back wheels and there is no sign of a leak. It might be the lines but I haven't seen a leak there either and the brake fluid level remains the same.

Can a vac leak and/or a bad master cylinder cause this? What about the ABS stuff? what else might be the problem?

[Pontiacdad]

You shouldn't bleed the brakes in the manner you described.
Start at the furthest distance from the master cylinder working your way to the closest.
Passenger rear
Drivers rear
Passenger front
Drivers front

keep adding brake fluid along the way and don't let it drop below the minimum level once started.

Abs will not cause the fade and the master cylinder will usually engage the check brake light.
A vacuum leak will also cause other problems like rough idle and stumble on acceleration.

[spoiledred94]

ThanksPD, Seems it must be a leak, but it acts like it's a big one and there's no fluid lost. Could it be a wheel cylinder or caliper? Also, I know my springs (adjuster or return I don't know for sure what they're called) on my rear brakes are broken off and I haven't had time to fix them. Kinda peeved I can't buy just the springs.

The Chilton made no mention of bleeding order. But I bled them in order just like my daddy taught me. Sorry if it sounded confused above. EDIT: I bled as indicated once and then redid the rears in order because I was not getting anywhere.

Man the car in your sig pic looks baad. What's your 1/4 et?

[1fatcat]

Most auto stores sell a brake spring kit for the rears.

[i<3bonbons]

No leak but pedal falls - bad MC.

[alec_b]

I second the bad master. Sometimes they leak from the rear lip seal, and that gets pulled into the vacuum booster, and then sometimes back through the vacuum line into the motor where it gets burned off. It's not too hard to pull the master and check for a leak at the rear, it's only two nuts. Don't even have to pull the lines.

[spoiledred94]

I second the bad master. Sometimes they leak from the rear lip seal, and that gets pulled into the vacuum booster, and then sometimes back through the vacuum line into the motor where it gets burned off. It's not too hard to pull the master and check for a leak at the rear, it's only two nuts. Don't even have to pull the lines.

I'll try that. What am I looking for? If there's fluid all around the lip seal can I replace it?


I'll call on the return spring kit. I worked at an auto parts store and saw only the whole brake rebuild kit.

[Ol' Timer]

What am I looking for?

Look no more!!! Just replace the Master Cylinder. Don't forget you need to "Bench Bleed" the master cylinder BEFORE you install it in your car. If you don't know how to do this there are many "how to's" on the internet. You will STILL have to bleed each brake cylinder (right rear, left rear, right front, left front) after you install the MC.

[spoiledred94]

It sounds like you know from experience. How do you know that's what it is?
Ok it's a safety issue and I haven't found anything else. I'll do it after I fix my transmission problem as it would be a waste of money if I can't fix my trans problem.


Thanks.
Kris

[Ol' Timer]

I have a very soft fading brake pedal. I've bled the rears twice and fronts once. There was a slight improvement but I have to pump once and then even though its stiff it fades all the way to the floor very slowly. I've been all around and in both the front and back wheels and there is no sign of a leak. It might be the lines but I haven't seen a leak there either and the brake fluid level remains the same.

Most of us have been here before. The symptom you describe fit a MC to a "T". Also, I would strongly recommend you check the front rubber brake lines that lead to your front calipers. If these lines look dry and cracked to you should replace these lines at this time as well. Member Bill Buttermore has a nice write up on bleeding the brake lines. It might even be in Tech Info.

Here's Bill's link on Bleeding Brakes.

http://www.pontiacbonnevilleclub.com/fo ... ?f=19&t=99

[spoiledred94]

I'll do it myself. Although my modo used to be that "it's the brakes, got to be done by a shop"

I'll check the front brake lines for replacement. Though this has gotta be it. I did a transmission replacement last month to the tune of $1500. That's LAST month.

Brakes are a first issue system. I had a friend the other day have a no fault accident and his air bags did not deploy. What gives? I thought those things were forever. I'd like to know how to test them.

What is it that gives on the MC? there's no leak at the main connection. I looked today.

Kris

[bill buttermore]

What is it that gives on the MC? there's no leak at the main connection. I looked today.

A master cylinder does not have to leak to fail. As the rubber piston cups wear, they can allow fluid to leak past the pressure side (brake lines) to the reservoir side of the bore. This can happen without a fluid leak to the outside. In fact, most master cylinders fail without a leak to the outside. Trust the advice you have received here. Your symptoms are exactly those of a bad master cylinder. Just change it out and follow the instructions provided with the new/reman MC for bench bleeding and the instructions linked above for bleeding your brakes.

And... replace the broken or missing hardware on your rear brakes. The parts are not expensive. Don't risk your life and the lives of others by driving with brakes that you know cannot function properly.