Spongy/soft brakes after pad change 2003 Alero 3.4

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moss

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Today I changed the front and rear brake pads on my niece's 2003 Oldsmobile Alero 3.4. The car has front and rear disc brakes. Also I bled the brake fluid starting from rear passenger, rear driver, front passenger and lastly front driver. Somehow the brake pedal stayed soft. I repeated the bleeding but still the same. I have changed brake pads and bled the brake fluid plenty of times, but never had soft brake pedal at the end. My first thought was faulty master cylinder or brake booster, but when I went to Autozone the guy there told me I need special scan tool for ABS. So I didn't buy a new master cylinder since I didn't want to replace a good part. Now I'm confused.
Do you guys know what scan tool the Autozone guy was talking about? Is it a special GM scan tool? Or should I ignore what he said and go ahead and replace the master cylinder?
Thanks in advance
 
I think that model's ABS unit has bleeders and can be manually bled, if that's what you were trying to do after replacing the MC. The bleeders can be hard to get to. When you bled it did you do it by pumping the brake pedal? Sometimes this can make the MC leak internally since it stroked into "bad areas, and sometimes the pedal will firm back up over time. This assumes you didn't allow the brake fluid level to drop to far when bleeding and allowing air into the MC and ABS.
 
Thanks for the quick reply. Yes, I bled the system by pumping the brake pedal, and I had a helper also. what do you mean the pedal will firm back over time? You mean overnight, in a few days, or weeks? You think I should wait a few days before I try to replace the master cylinder?
I'm pretty sure I didn't starve the reservoir of brake fluid, but it did go on the low side once. If air got into master cylinder, does that mean it's gone?
 
I mean the master cylinder can over time stop internally leaking and seal, and so the pedal will firm up. It might be a day or two, or even a few weeks, it's hard to predict. I've seen this before several times. But if the pedal height is decent I'd wait and see.

It doesn't sound like you got air in the MC, but if you did then you'd probably need to bleed the system at the ABS.
 
The pedal height is fine, it's just spongy. I will take your advice and wait a few days. Thanks again.
 
You are more than likely going to need the scan tool to burp the air out. Sorry. Call around, some dealers are going to be more snarky about saving this than others.

Another thing you can try, because you have nothing to lose, is finding an empty sandy lot and activating the ABS a few times.
 
Try putting teflon tape on the bleeder screws and attach a tight fitting plastic or rubber hose,put the hose in a empty can as close to the ground as possible.The tape is only to keep fluid from going all over the caliper.
Leave the bleeder open for a few min making sure to keep the MC full.Tap the caliper lightly a few times with a rubber mallet.Do not pump or open and close the bleeder,when finished simply close the bleeder.Do this for all 4 starting at the right rear.

It helps to put the axle your working on stands to get that end in the air a little.
 
Leave everything tightened, engine off, and just quickly pump the brake pedal completely to the floor, for about 25 times.


-------------------------------------

1999 Alero 3.4L
 
I'm a little confused... In your first post, you didn't mention replacing the master, only wanting to.. Yet many others are talking like you did... Did I miss something?

How did the brakes feel prior to replacing the pads? Is the soft pedal a new occurrence? Why did you bleed the brakes after replacing the pads?

You do need a scanner capable of reading ABS systems which all aren't, however, the ABS is likely not your culprit here and changing the master doesn't require reading the ABS computer.
 
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Did you machine the rotors? It sounds like the car doesn't stop very well. Sometimes American cars have a rather soft pedal so it may just be that the pads aren't seated because the surface finish on the rotors is incorrect.
 
Thanks for the replies gentlemen. I did bed in the new pads, I took the car on an empty highway close to my house and made several high and slow speed stops. I haven't changed the MC yet. I didn't machine the rotors, I never do. I usually just measure rotor thickness, if under manufacturer's specs than I just change the rotors. I did also pump the brake pedal to the floor several times. The pedal is definitely a lot softer after the pad change. I checked for a leak, but couldn't find one, also fluid level in reservoir didn't change overnight. Also the pedal height is where it should be, it just is softer than before like it's not holding pressure.
I will drive the car on a sandy lot or on grass to activate the ABS a few times. I hope that will help. Also will try pumping the brake pedal all the way down 25-30 times like mentioned above. If in a few days the pedal doesn't get firmer, I will go ahead and replace the MC.
 
Those pads have to seat and mate with the rotors.
Your perception is normal, to various degrees.
Be aware that on tiny slip up when bleeding will negate all the good bleeding!
 
I'm still really think the master cylinder seals got a little disrupted when the pedal was stroked to floor during bleeding, and I don't think you have air in the system. Although air in the system is a possibility. You might consider getting a mighty vac tool to bleed the brakes in the future.

Does the pedal seem to drop lower as you press on it and is sometimes lower than at other times? I think this ABS has bleeders and can be bled without a scanner but replacing the MC and bleeding the whole system again would be a major pain. Since you have decent pedal height, I'd just continue running it and see if the pedal firms up.
 
Which way did you install the wear indicator pad ? The Alero front brake pads must have the pad with the wear indicator tab on the inside of the rotor for the pads to slide properly.

Also, the self-adjusting is done by several slow stops. Drive at about 20 mph, and use very light pedal pressure to stop.
 
Originally Posted By: mechanicx
I'm still really think the master cylinder seals got a little disrupted when the pedal was stroked to floor during bleeding, and I don't think you have air in the system. Although air in the system is a possibility. You might consider getting a mighty vac tool to bleed the brakes in the future.

Does the pedal seem to drop lower as you press on it and is sometimes lower than at other times? I think this ABS has bleeders and can be bled without a scanner but replacing the MC and bleeding the whole system again would be a major pain. Since you have decent pedal height, I'd just continue running it and see if the pedal firms up.


You were correct, brake pedal got harder as time went by. The MC seals must have been disrupted during bleeding, but everything seems fine now.
 
Good to hear the issue resolved itself, Thanks for updating
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