Reasons for Spongy brake pedal?

I recently changed my brake pads, rotors, and shoes (car has rear drums and front calipers), and I also bled the old fluid out and put new fluid in. This was my first time ever doing it, and I'm a little scared I let the fluid get too low and therefore I sucked air into the master cylinder's piston. So, I'm going to bleed to master cylinder and rebleed the brakes this weekend, however, I'm looking for ideas of what else it could be if this doesn't work.. Thank you!

brake lines?

I'm going to re-bleed them this weekend, after I bleed the master cylinder.. So are you saying they could be damaged? If so, how might i check this.. There's no physical leak I can see. Thanks!

Spongy brake pedal is most likely air in the brake lines. Also you need to bed in the pads and rotors. This involves getting them up to high temp to develop a transfer film at the pad and rotor interface. This is the procedure I usually follow and works well...

  1. After installing new brake pads, make 6-to-10 stops from approximately 30-35 MPH applying moderate pressure.
  2. Make an additional 2-to-3 hard stops from approximately 40-45 MPH.
  4. Allow at least 15 minutes for the brake system to cool down.
    After step 4 is completed, your new brake pads are ready for use.

What exactly do you mean by 'do not drag brakes'? But thanks, I have heard of bedding them in, but I haven't tried it yet.. Thank you!

Drag brakes means do not sit on the brakes either at a stop or ride them when driving. After step 2 the brakes are going to be pretty hot, if you are at a stop light for 2 min with your foot on the brake pedal and the Pad sits on one part of the rotor they can tend to stick or even warp the rotor (due to uneven cooling). Its like cooking an egg in a hot stainless steel pan, if you leave it in one place it will stick...

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Oh gotcha, Thank you! I'll definitely do this today

You can put a clear plastic hose on the bleed fitting that way you can visually inspect the fluid for bubbles. Using DOT3 or sythetic?
Leak will show up easy. Master cylinders do wear out but in this case it is safe to say air buble. The plastic hose also help prevent any air getting back in. Hope this helps

Thanks, I'm using DOT3, and I've been using a clear tube on my calipers/drums, and I plan on picking up a master cylinder bleeding kit from oreilly's this weekend.. I'm definitely scared that it could be my master cylinder that went out, but it's good to hear that an air bubble is likely!

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You have air in the brake system, proper bleeding should remove the air, a good rule of thumb is since you let the master cylinder go dry/too low and got air in the system when you think you have it all out do it again, start at the wheel that is the furthest away from the master cylinder (normally right rear), then do the left rear, then the right front, and finishing with the left front. Another thing to consider is since you replaced the rear shoes make sure when your all finished that the shoes are adjusted up to the drum (slight drag) and that the self-adjusters are free and working.

If you did not have a spongy pedal prior to the brake job air is the issue.

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I didn't have a spongy pedal before, and I've heard that bleeding all the brakes won't get air out of the master cylinder.. Any truth to this? Thanks, and how would I go about checking the adjusting the shoes on the rear drums? I thought they just adjusted naturally overtime.. Thank you!

Try replacing your brake lines. Ideally with a set of braided stainless steel brake lines.

All rubber parts on cars go bad long before the car does. Old rubber brake lines balloon up when you stomp the pedal resulting in a mushy feel. It you are sensitive enough to notice, steel brake lines will give you a more precise feel.

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It sounds like you need to get the CHILTON or HAYNES books for your car. They come in 2 flavors, the ones you can get at the auto parts store (which aren't very good) or the expensive one the mechanics use. I happen to have a PDF of the dealer repair manual for my vehicle. When I do a repair, I only print the pages I need.

The first place to start is to find the correct forum for your car. May I suggest starting with the SCCA (Sports Car Club of America) or Wheelwell (PC Part Picker for cars)? you did get air in the lines (you didn't remove the calipers from the hoses?) some master cylinders can be bled separately most can not unless they are removed and bench bled (not necessary in this case) almost always you can remove the air from a master cylinder by bleeding the wheel cylinders and calipers it just takes a lot of time.

To bleed the brakes properly without a pressure bleeder or vacuum bleeder you need two people, one to work the brake pedal and one to open the bleeder. The person working the pedal is actually the person who has to pay attention to what he is doing, you never want to pump the pedal only apply pressure to the pedal, then open the bleeder while the pedal person lets the pedal sink towards the floor but not hitting the floor (don't bottom it out) then close the bleeder before letting the pedal return, just keep repeating the process 6-10 times per wheel, if you are getting air of course keep working that bleeder till you get a solid stream of fluid then move to the next wheel.

At some point the person working the pedal will notice the difference in how tight or stiff the pedal is (not spongy) and at this point you can continue or quit, a note of caution you need to keep a eye on the master cylinder while bleeding and keep topping it off to ensure it doesn't go dry and you have to start all over.

Some older cars have a red brake light on the dash, if that light is on after doing a brake job it means you got air in the system and the proportional valve is off center because of the trapped air, if the light is on while bleeding it will go out once you have all the air removed and the valve can return to center, this light gives you a indication if you still have air in the system but don't confuse it with lights on more modern cars that is measuring the height of the fluid in the master cylinder.

Last thing is that older cars with power brakes might need to be running to completely bleed the system and get the proper feel at the pedal, the assist that the brake booster creates when the engine is running is necessary to get the proper pedal travel.

On the rear brakes to adjust them there will be a knock-out or a rubber plug either on the face of the brake drum or on the backing plate that holds the shoes, wheel cylinder, springs, anyway you can use a tool to rotate the star wheel on the auto adjuster from outside and turn the drum until you hear it slightly dragging, don't get it too tight! or they make a measuring tool that you measure the inside dimension of the drum and use that tool as a guage to run the shoes out manually before installing the brake drum.

The adjusting spoon or tool looks like this....

The measuring calipers look like this....

Most cars and trucks that have rear drum brakes get their pedal height from the rear brake adjustment, what that means is that the amount of travel the pedal has to travel before starting to apply the rear brakes, in most cases it shouldn't make the brakes pedal feel spongy but will increase the travel the pedal has to go which might give the perception of being spongy to some drivers.

Anyway hope that helps.

This might also help...

Wow, thanks a ton for all this information!! This will definitely be the first thing I check seeming it's so easy! I did have to loosen the shoes with this adjuster to get the drum off, however, i always thought the drums would re-adjust automatically through some driving time, I'll make sure I tighten those up! Thank you!

Bled master cylinder, readjusted rear drums, and bled all brakes again.. Still having symptoms so I decided to visually inspect my calipers and it seems my front passenger side caliper's piston seal is uncentered, I'm going to go take some pictures now and upload them, but if anyone sees this before I upload them, do you have any advice.. Return it? Stick a screwdriver in there and try to pry it out? Or is it not a problem at all.. Thanks

EDIT: Adjusting the rear drums did help a bit, but definitely not as much as I'd hoped.

EDIT #2: I should mention that there is no visible leaks on the caliper, and no puddle under it when it sets overnight.. Here are the pictures, the first picture is the "good" side of the piston, where the seal is right up against the piston, the second picture is the "bad" side of the piston, where the seal looks like it's hanging off:

EDIT #3: Also, the rotor that sits between this caliper can be moved back and forth when the wheel is off (not with the wheel on), while the other side can not. Also, when I took the picture caliper off it kind of slid off when unbolted, while the other stayed stuck (even after un-bolting it) until i pulled it off.

When you say "return it" does that mean that you installed rebuilt caliper when you did your brake job? the seal around the piston is what is called a lip seal, it is just to keep trash out (dirt dust) of the bore that the piston moves in and out of, the actual sealing of the caliper piston is a o'ring that is back further on the piston....something like this picture but the placement is different on different brake systems.

If the problem is just the seal it's not a issue but if the piston itself is cocked in the bore then yeah it's defective, like I asked above if you replaced your calipers? then I'd ask how you bled them, as far as the procedure you used.

It might also be of help to know what car (type, make age) you are working on.

I'm an idiot I can't believe I didn't mention this.. I did replace one caliper because when I tried bleeding it the bleeder screw snapped, so I replaced the caliper with a new NAPA one (this is why I mention returning it). I have an 07 cobalt ls with the 2.2l motor. I went in the order of RR, LF, LR, FR.. This order was recommended by my Haynes book

EDIT: do you mean the piston cocked in the bore like it doesn't move? If so the piston does move.

Is this a system that needs a computer to bleed the abs?

I know on all the newer toyotas you can not reliably bleed the brakes.

With this being an 07, I would call the dealer and ask if it needs a computer.

There's no abs