I changed out the front brake pads on my 97 Nissan Altima.  I have done this
several times in the past with no problems.

I had to force the piston back to allow the caliper to fit over the new
pads.  I always do this the same way.

Now, the brake pedal is very spongy, and the fluid reservoir is over-full.
Did I force the fluid backwards into the reservoir?   I don't think any air
was introduced into the system.  I don't see how it could have, nothing was disconnected.

Is it possible that over time, things will work themselves out right where
they were before or do I have to do something to correct this?

hmm, that  is  interesting.  i  can't  help  much except drive  it  around the  block  and  see if  it  feels any different and if  it does, bleed the brakes  that you changed  some  and see if there  is   fluid  in there.

I'd start by removing some fluid from the master cylinder so that the level was in range.

I like to start with the easy fixes.

It sure sounds like air got in there.  When changing pads I always crack the bleeders to make it easy to push the pistons in, and give the whole system a proper bleed when I'm done.

Did you take the cap off the fluid reservoir when you did the work?  You needed to.  You also need to have someone help you watch that it doesn't overflow.  A turkey baster is sometimes needed to take some fluid out.  

You need to have the brake system bled now.  You may have damaged the caliper piston as well.  Watch the rotor on that wheel.  If it rusts over in a day or two even when you have been driving it then it is not working.  Trust me, it doesn't take much to screw it up.  

Quoted: I'd start by removing some fluid from the master cylinder so that the level was in range. I like to start with the easy fixes.

This may help but I doubt it (if you have already pumped the pedal).  Remove the EXCESS fluid then try pumping the pedal.  It may just need to redistribute the fluid back through the system properly.  If it works and the pedal firms up be sure to recheck the fluid a couple of times.  It may need fluid put back in.

When you compress the caliper piston, you do indeed send the fluid back into the brake fluid reservoir. That is why you should do this step slooowly. If there is too much fluid now,it means that someone added fluid to a system that had not lost any fluid in the first place (The fluid level in the reservoir will go down as the brake pads wear,because it takes more fluid to compensate for the pad wear.)
   If you compressed the caliper piston too quickly, you might have introduced air into the system, and it will have to be bleeded out. I use one of those "Mity-Mite" vaccuum pumps to make brake bleeding an easy, one person job. (No more yelling at your wife when she presses the brake pedal at the wrong time!)

Do not, repeat, DO NOT, get brake fluid on the paint.  It will eat clear coat like Oprah eats muffins.  I recommend washing the vehicle as soon as you are done with repairs just to be safe.

I had an Oldsmobile with a nice set of hand prints crazed into the clear coat where I grabbed the fender with fluid on my hands.  Lesson learned.

Quoted: If there is too much fluid now,it means that someone added fluid to a system that had not lost any fluid in the first place (The fluid level in the reservoir will go down as the brake pads wear,because it takes more fluid to compensate for the pad wear.)

That is precisely what happened.

Okay, I just took the excess fluid out.  I'm going to try pumping the pedal, take it for a spin and see what happens.

Thanks for all the help so far and I'll let you know how it goes.

Quoted: Quoted: If there is too much fluid now,it means that someone added fluid to a system that had not lost any fluid in the first place (The fluid level in the reservoir will go down as the brake pads wear,because it takes more fluid to compensate for the pad wear.) That is precisely what happened. Okay, I just took the excess fluid out.  I'm going to try pumping the pedal, take it for a spin and see what happens. Thanks for all the help so far and I'll let you know how it goes.

"testing" a brake job is always exciting.

try adjusting the rear brakes to get a nice pedal

Alright, took it for a spin.

I'm beginning to wonder if this "spongyness" is in my mind or not.  Could it be that the new pads don't have the same level of "bite" as the old ones causing me to have to press a little harder to get the car to stop?

Not sure what to do now.

I will bet some of it is in your mind. However, if you have never changed the brake fluid in the system, that is bled it out completely and refilled, expect some problems in the future. 9 years is a lot of accumulated gunk/rust and water in the system.
Notice the brake fluid is black or brown now and not clear like it comes out of the bottle.

It's slightly brown, yes.  Golden rather.  I'd have to look at the fluid in the bottle to see how different it is.

In retrospect, I probably should have taken it to a garage, but I knew it only really needed pads and they rake you over the coals.  Can't really dump that much money into the car.  I really only need about another 3 years of service out of the thing.  The car has 102k on it now, I generally put about 15k on a year.

Brake pads do have to bed in.  Drive it easy for a few days until the rotors and pads get real friendly with one another.  It might be good to use paper towels to get nearly all the old brake fluid out of the reservior and then refill with fresh and bleed the brakes until fresh fluid is coming out the bleeders.  You should really do this at least every 3 or 4 years.  Especially with anti-locks.

Quoted: When you compress the caliper piston, you do indeed send the fluid back into the brake fluid reservoir. That is why you should do this step slooowly. If there is too much fluid now,it means that someone added fluid to a system that had not lost any fluid in the first place (The fluid level in the reservoir will go down as the brake pads wear,because it takes more fluid to compensate for the pad wear.)    If you compressed the caliper piston too quickly, you might have introduced air into the system, and it will have to be bleeded out. I use one of those "Mity-Mite" vaccuum pumps to make brake bleeding an easy, one person job. (No more yelling at your wife when she presses the brake pedal at the wrong time!)

The vacuum type can cause cavitation from the pressure drop, which means bubbles in your fluid.  I replaced my bleed screws with speed bleeders, which have check valves in them, you just hook up a catch bottle and bleeding becomes a one-man operation.

Did you change the rotors ?

If not, and they're not pretty close to flat, then you'll have decreased contact between the rotor and the pad lining, requiring you to step harder on the pedal, to get the same amount of 'stop'.

If you feel any pulsation in the pedal, this will indicate a warped/out of true rotor as well.


Rotors are cheap..... always best to just replace them, unless you get your old ones turned and they have enough metal left to work safely.

You didn't change the rotors or have them turned? the new pads will have to bed into those old rotors again to get the same feel. Nowdays, I just buy new rotors at the same time I buy new pads,and just replace the whole mess at once. (The rotors all come from China now, and fewer and fewer places are bothering to re-surface old rotors anymore.)
  You may have gotten a different type of pads this time,instead of the type that were on the car (Semi-metallic,metallic,etc)
  I live on a dirt road,which eats up pads and rotors in no time at all. I've done so many on my cars that it takes less than a half-hour to do the front brakes these days.

Does it have antilock brakes ?

See it's like this . If your car has anti lock brakes
when your force dirty fluid back through the system
there is a chance that you can lodge debris in the
hyd controller , hanging a dump valve open and end up
a spongy pedal

I get 1-2 in my shop a year from people who
do this . The only fix is a new Hyd controller
because it's a non servicable sealed unit .

Hopefully you just cocked a caliper piston and
got some air in the system , but it's rare to have that
happen and not leak some fluid out the caliper piston boot .

For future refrence , if you have anti lock , you should open
the bleeder before compressing the piston and allow the dirty
fluid to escape . If you do it right you won't have to bleed the
system when your done .

Anyway .. I'll wait and see what you find . Good luck

Guys, thanks again for all the replies!

No ABS on my car, so no worries there.  The rotors look brand new still!  No noticible wear at all.  

Chrome, what do you mean by 'cocked the piston?'  I did have the caliper upside down and stuff in an effort to get the piston to compress.  Oops if that's the wrong thing to do.  But I have done the same thing in the past w/o any noticable problems.

But, there was no fluid leak anywhere to the best of my knowledge.

What he is talking about is if you pressed on one side rather than the middle, you can cock it sideways a bit. There is only an o-ring seal that stops the fluid from leaking by/air coming in. So if you moved it sideways and not straight back, you could have put air in. But as he said, you would see some fluid around the dust boot on the caliper.
You sould still change out the fluid if you can. I have seen black fluid come out from people that never bothered to change the fluid. They had problems when they were in stop and go traffic and overheated the brake fluid that was mostly water at that time. So they got a steam bubble in the line and lost brakes till the pumpped it up and collapsed the bubble.

What he is talking about is if you pressed on one side rather than the middle, you can cock it sideways a bit. There is only an o-ring seal that stops the fluid from leaking by/air coming in. So if you moved it sideways and not straight back, you could have put air in. But as he said, you would see some fluid around the dust boot on the caliper.
You sould still change out the fluid if you can. I have seen black fluid come out from people that never bothered to change the fluid. They had problems when they were in stop and go traffic and overheated the brake fluid that was mostly water at that time. So they got a steam bubble in the line and lost brakes till the pumpped it up and collapsed the bubble.

Unfortunately, I think bleeding out and refilling the brakes is beyond my abilities.  At least, I don't know how to do it.

As said above, use a mighty vac or speed bleeders. Both availible at your local parts store.
The mighty vac is just a vacuum pump that you use by hand. You crack open a bleeder screw and hook up the hose to it and suck the line dry. Move along till all of them are empty. Then refill the master cylinder and suck till you get fluid. This is my choice since you get all the old fluid out, with little or no mixing.
BTW you start with the wheel furthest away from the master cylinder working to the closest. So Right Rear/passenger rear, driver rear, passenger front, the driver front for bleeding. Same no mater what you use to do this.

Speed bleeders replace your bleeder screws. They have a check valve built in. So you just loosen them and put a hose at the end to catch the fluid. Keep your master cylinder topped off and just pump the pedel till you get clean fluid out.

You must be careful even when changing your brakes, especially if you don't change your fluid not to press the pedal all the way to the floor. You can screw up the master cylinder that way.
What happens is, your pedal only moves so far durning normal operation. Say for 3 years you only move the pedal 6 inches. When you change pads, or bleed brakes, you can push the pedal to the floor if you don't make a point not to. The piston in the master cylinder then travels farther than it normally does. The reason this is a problem is that during its normal travel range sometimes you build up gunk at the edge of its travel path, or even a ridge of sorts that when you push past, will tear the seals on the piston. Thus killing your master cylinder.

Everything seems cool now.  Maybe I'll just leave well enough alone.  If I go trying to change the brake fluid (and I don't really know what I'm doing with that) I stand a good chance of screwing things up.

I'm not a mechanic, but I've changed dozens of front brake pads/rotors.

Feeling spongy is a symptom of an air bubble.  But it could be a symptom of a cocked piston,
or an improperly installed pad.  (slipped out of place while installing, etc.)

If the car doesn't pull to one side when you brake, then you pretty much know it is an air bubble.

Since you didn't replace a caliper, the only place the air could have gotten in is the master cylinder.

(unless you have a very tiny  hole in a brake line, which happened to me a few months ago)

And since you pushed fluid back into the master cylinder, you know the bubble is probably
in the piston area, and not in a brake line.

As odd as it sounds, this problem will probably go away on it's own.
I've had it happen on a couple of different vehicles, and the bubble has worked it's way back out.

To help the bubble come out, you can tap on the master cylinder with a wrench or hammer.
I have found that this is often enough to knock a bubble loose.

You have to bleed the systemat least part way.

How you got away without doing that in the past is a mystery to me.

Not really. If all he did was push the pistons back in, the system never gets cracked open in the bottom, so no bleeding required. Just take the extra out of the top.