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I replaced my brake pads this weekend and now my brakes seems like they are much softer than before. I can easily put the brake to the floor. The vehicle is a '98 Chevy Malibu. I have seen some references to bleeding the brakes. Could that be it?

Update: One other question I just thought of. Can the reservoir be too full? Could that cause problems?

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3 Answers 3

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Bleeding the brake will remove air in your brakes line. If you only replace the pads without disconnecting any brake lines, no air should have entered the system.

BUT, since you have played with your brakes, and with the symptoms you have, you should bleed the brakes to remove any air. Air in the brake line can make the pedal softer and can also prevent you from braking. I've changed my brakes (pads, rotors and calipers) this summer and had a soft pedal and re-bleeding the brake solved my issue.

Also, if your brake line are old they can bulge under the brake fluid pressure, which can also create the soft pedal as you described. Then you can change your brake lines and even switch them to stainless steel lines that won't bulge, but are way more expensive!

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Check your fluid level. If it is abnormally low, you may have a leak. Also, if the reservoir is completely empty, you may have to follow special procedures to bleed your master cylinder and/or ABS pump.

You will want to bleed your brake system until you have completely replaced the old fluid with new fluid. If you routinely bleed and maintain your brakes, this is not always necessary. But if you do not know the last time your fluid has been completely flushed, I recommend this highly. Brake fluid is cheap and a power bleeder makes the job easy (I think I answered another question of yours regarding power bleeders).

While bleeding check for any leaks around the lines and calipers. You can also pull the calipers off and check your pad wear.

If, after bleeding, the pedal is still soft - I'll just say I've had this scenario on 3 different vehicles and on all 3 it turned out to be the master cylinder. I can't tell you how to tell for sure if this is it. I simply swapped it as the next step after a couple of bleeds failed to fix the problem.

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Both the other answers cover bleeding well, however if you didn't open the hydraulic system (other than the master cylinder cap) then I doubt it's air in the line. My answer assumes a couple of things, you replaced the front pads and you did not turn (resurface) the rotors.

During normal brake operation the rotors don't wear evenly, they may be thinner on the outside (farthest from center) than on the inside for example, or other irregularities. Note I am not talking about "warped" as that would cause a vibration when braking. When you install new pads that have a nice flat surface and the rotors aren't because they haven't been turned the brake pedal will feel spongy. This is because not all of the pad is in contact with the rotor. This will eventually go away as the pad wears and all of the pad comes in contact with the rotor.

Another cause could be not burnishing the new pads. You should always burnish brakes after every brake job, which simply means make several stops from 30 MPH, allowing time for cooling in between stops to seat the pads to the rotors so to speak. You can find more info here At Bendix, we highly recommend that new pads and shoes be broken in properly.

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I did take a spin and slam on the brakes some. However do to another issue I found (a broken sway bar), I didn't want to drop the front-end too much by slamming on the brakes. I will be bleeding the lines to see if that helps. At least get new fluid in the lines. –  Mike Wills Oct 25 '11 at 13:06
    
@MikeWills Slamming on the brakes in not the same a properly bedding (burnishing) them. [Slamming on the brakes may cause glazing of the pads which will make matters worse.] A crucial part of the bedding process is to get the brakes hot enough to make sure the resins present in the pads are baked out of the pad. Not doing so may result in "green fade" (see about 1/2 way down on the StopTech Page on Bedding Brakes) . –  jwernerny Oct 26 '11 at 12:59

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