Do I have to bleed the brake line after replacing brakes?

[nobb]

My car has about 90 000 kms on it and I am still on the stock brake pads and shoes.

There is still a fair amount of material on the brakes, but I think Ill replace the pads and shoes myself this summer. Right now, the brake feels a bit soft and spongy. Is that normal for brakes wearing down, or is it perhaps maybe air trapped in the brake line?

I am just wondering if you guys think that when I replace my brakes that I should also bleed the lines as well? I am planning on learning to do everything myself btw...I have never done any brake work before.

 

[Bignate603]

Your pads being worn shouldn't make it feel soft and spongy. Bleeding them to see if it fixes it would be a good idea.

 

[CycloWizard]

If the brakes are original, then it almost has to be a bad master cylinder. There shouldn't be any air in the lines and, as bignate said, wear shouldn't cause the brakes to feel spongy.

 

[Sukhoi]

Originally posted by: CycloWizard
If the brakes are original, then it almost has to be a bad master cylinder. There shouldn't be any air in the lines and, as bignate said, wear shouldn't cause the brakes to feel spongy.

What goes wrong in a master cylinder that would cause this? I have very spongy brakes. About a year ago I had my entire brake system flushed when I was having other work done, but the sponginess did not change. Would it be possible for air to be stuck in the master cylinder itself after a flush? The sponginess hasn't gotten any worse, so it's not really something I want to spend money to fix. Now if it is some sort of bad seal or whatever in the master cylinder, would that cause uneven braking? My car doesn't brake entirely straight but I always thought it was more related to alignment than uneven braking. Car is a '95 Corolla.

 

[StageLeft]

Originally posted by: Sukhoi

Originally posted by: CycloWizard
If the brakes are original, then it almost has to be a bad master cylinder. There shouldn't be any air in the lines and, as bignate said, wear shouldn't cause the brakes to feel spongy.

What goes wrong in a master cylinder that would cause this? I have very spongy brakes. About a year ago I had my entire brake system flushed when I was having other work done, but the sponginess did not change. Would it be possible for air to be stuck in the master cylinder itself after a flush? The sponginess hasn't gotten any worse, so it's not really something I want to spend money to fix. Now if it is some sort of bad seal or whatever in the master cylinder, would that cause uneven braking? My car doesn't brake entirely straight but I always thought it was more related to alignment than uneven braking. Car is a '95 Corolla.

I am sure that a badly done brake bleed could get some air where it shouldn't be and increase sponginess. To answer your other question, I'm not sure.

I will add that although wear on the brake surfaces won't make them feel softer, if you go cheap on the replacements like I did a while back (original rotors were turned but I used super cheap semi-metallic pads), braking response was less and I just put up with it for about 50k miles before replacing them this year with ceramics and I was back in business with grippier brakes again.

 

[dud]

Get someone to help you bleed the lines. If, after you are done it still feels spongy then the next thing to check is the master cylinder.

 

[radioouman]

A bad master cylinder will allow fluid to go back into the resevoir when you hit the brakes.

 

[Sukhoi]

Originally posted by: radioouman
A bad master cylinder will allow fluid to go back into the resevoir when you hit the brakes.

Is that something I could visually see?

 

[radioouman]

Originally posted by: Sukhoi

Originally posted by: radioouman
A bad master cylinder will allow fluid to go back into the resevoir when you hit the brakes.

Is that something I could visually see?

No, not at all, although you might be able to hear it. If you put your foot on the brake pedal you might be able to hear the fluid flow back past that worn (or broken) o-rings around the piston. It will just flow back into the resevoir and won't leak.

 

[Sukhoi]

Originally posted by: radioouman

Originally posted by: Sukhoi

Originally posted by: radioouman
A bad master cylinder will allow fluid to go back into the resevoir when you hit the brakes.

Is that something I could visually see?

No, not at all, although you might be able to hear it. If you put your foot on the brake pedal you might be able to hear the fluid flow back past that worn (or broken) o-rings around the piston. It will just flow back into the resevoir and won't leak.

Hmm, I may try that out tonight. My sponginess was the same before and after the brake flush, so either the same pocket of air stayed trapped the whole time or there's probably an internal leak in my master cylinder.

 

[radioouman]

Originally posted by: Sukhoi

Originally posted by: radioouman

Originally posted by: Sukhoi

Originally posted by: radioouman
A bad master cylinder will allow fluid to go back into the resevoir when you hit the brakes.

Is that something I could visually see?

No, not at all, although you might be able to hear it. If you put your foot on the brake pedal you might be able to hear the fluid flow back past that worn (or broken) o-rings around the piston. It will just flow back into the resevoir and won't leak.

Hmm, I may try that out tonight. My sponginess was the same before and after the brake flush, so either the same pocket of air stayed trapped the whole time or there's probably an internal leak in my master cylinder.

A master cylinder was $30 for my '93 Dakota (just replaced it this spring). I don't know what it would cost for your car. They also recommend filling the master cylinder with fluid before installing it, otherwise you will get air trapped in the master cylinder. Also, plan to bleed the brakes afterwards because you will get air in the lines. (Lots of bleeding)

 

[AMCRambler]

Worn brakes can get you excessive pedal travel, meaning the pedal goes down further before the brakes start grabbing. Disk and drum brakes on most newer cars automatically adjust themselves to a certain point as the brakes wear though so pedal travel shouldn't really be huge unless they're real worn. Getting a bad bleed job done could get air trapped in your master cylinder. If they let the master cylinder run dry while bleeding the brakes and then filled it and resumed bleeding there could be air trapped in it. It would take a real numb skull mechanic to do this though and at the very least they should test drive the car after the work is done. If they gave the car back to you and the brakes failed and you got killed or seriously injured hooo weee what a liability that would be.

My guess is your master is shot and you need a new one. They are pretty cheap if you wanted to buy one and replace it yourself, if you're handy. If not a decent shop shouldn't charge you more than 2-300 for the work. They can also diagnose it to be sure.

 

[thecritic]

A bad brake flush job can cause the pedal to feel worse. I've have mixed results with those "one-man" bleeders; I've found that following up with an old-fashioned bleed always delivers the firmest pedal.

Worn out pads shouldn't affect the pedal feel. However, a brake flush and bleed can restore the pedal feel.