Hi, yesterday i turned 16 and got my liscendes so after school i went to my friends which is like 12 miles away, on my way back i noticed my brakes were getting alittle mushy so i didn't think to much of it other than i'll look into it later. Also whenever your driving and you like hold the brake at a certain point for a while the pedal starts to travel but it wasn't a lot. Then that night i went to a Blink 182 concert w/ my friend and i just droped my car off at her house, whenever i got back i started the car i pushed the brake and it easily went to the floor and the brake light came on, and then i pressed it again and again, it got alittle harder but not much. It was doing the same thing today, it will stop the car but i haven't went over 25 since i was just driving in town, but it's really freaky. We replaced the master cyl a few weeks ago and bled the brake lines, and the pads are good so what is wrong? Or what should i check for, it does this everytime time i push it. Let me know!

Alex..

It could be a leak, did u check fluid in the Resovoir? Either that or it could be your master cylinder needs changing/rebuilding. This is just from my expieriences.

Check your brake fluid level in the master cyl. If its low, then obviously add and check for leaks. If not, you may have to re-bleed. Sorry if this isnt much help but Ive only worked on Fiero brakes once and I swore Id never do it again lol.

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My 7 Fieros

I check the fluid today it is fine, we replaced the master cyl i think 2 weeks ago w/ a new one. Where should i check for leaks at? But the fluid was full when i check it this morning before i went to school. lmk

Alex..

Likely the new MC is bad. Most likely it's secondary piston.

Are you certain it's a new one? Not a rebuilt? I never use rebuilt aluminum MC's if I can avoid it.

Pumping it that much would expose a leak quickly as it would rapidly exhaust the MC tank.

Are you certain that the brakes aren't dragging? That could have boiled the fluid but you would probably have smelled it if it got that hot. I still think the new MC is bad.

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11-Sept-01, The day the world as we knew it ended.

[This message has been edited by theogre (edited 09-18-2001).]

Alex:

I have to agree totaly with theogre.

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It is a rebuilt one... LoL we got it at Oreily's. I don't think they were dragging, the right rear one did for a while but i haven't noticed it lately, but i didn't smell anythign wierd whenever i got out of the car. We were going to rebuild the rear calipers but haven't got around to it yet. So you think the new MC is bad, the first one wasn't bad but we thought it was at first. I'll go look for leaks after i get offline, any more ideas? LMK.

Alex..

Rebuilt Al MC is only as good as the rebuilder. I have little doubt it's your problem. It should have at least a short warantee on it.

is there any way for me to check to see if it is the MC? I don't mean to sound like im doubting you but i just wanna see if i can avoid changing it again. thanks,

Alex...

I'm not sure if you disconnected the calipers at all. If so, you might have an issue with those copper washers. I'm not sure whether or not there is supposed to be 2 sizes, but when my rear hose leaked, I switched it with a shorter washer (I just had a pile of them) and the leak stopped. Just another option to consider if it applies.

If it's not losing fluid, it's the MC. Everything else that causes this, except air in the system, would have a leak.

You could try rebleeding and see if it helps but I doubt it.

The keys here

It was working normally then went mushy.
Stayed that way and wouldn't pump up.
No Fluid loss.
Suposedly, no calipers are dragging and causing a fluid boil.

It could be the secondary piston or the quick takeup valve. Since you can't pump it up then I'd have to say piston.

Hey man here is something very wierd that I had a problem with:
My car would start to do the samething but after along drive with realitively few stops and little breaking. The breaks were good. The master cylinder looks new. The booster works great and there were no leaks! The only thing i could figure was that the previous owner used the wrong fluid and it was boiling but realized that the breaking I was doing was extremely light. I was told to use the Emergency break when I park it to align the breaks. Since I have done this I have had no problems. I dont understand it. Nerver heard of this before but it worked. If I forget to do this then the breaks start going to the floor and the Bake light comes on and only stops after pumping fast. try it it cant hurt.

falconhulk,

The symptom you describe often indicates the MC has a bad quick takeup valve. This can only be fixed by MC replacement.

The QT portion of the MC will makeup for even pretty serious rear caliper clearance problems. A bad QT valve kills this function and the main bore simply can't handle the volume demands. (Explanation of the quick takeup function is in the brake upgrade article in my cave.)

In all honesty I'd have to recomend you replace the MC. If at all posible, get a new one not a rebuilt. Even if you have to special order it. I'd also do the manual rear caliper adjustment in my brake service article. That will set the base clearance in the calipers to where it should be.

It certainly wouldn't hurt to try the manual adjustment first but I really think you both need to replace the MC.

Thanks theogre! I am going to take it back to the dealer and have him check this again. Its real strange though I have not had this problem since he told me to use the e brake. Maybe just a coincidence?

The E brake will keep the calipers in adjustment. This is a good thing. The fact that you are dropping to the floor with even a small amount of pad wear is what makes me suspect the valve in the MC. A failure of that valve means the brakes still work but they won't tolerate any out of adjustment condition.

Even when my rear bakes were considerably out of adjustment, my pedal never dropped below the hieght of the gas pedal. (Gas pedal with your foot off it.) Now that my rears are set correctly the pedal doesn't even drop that far. (How far out? I could have gotten two of the shims required for the manual adjustment in one caliper. the other was pretty loose.)

Allot of how the valve works is explained in my brake upgrade article. I'll try to sumarize it.

We'll skip a bunch of math... Lets say the MC without the QT function has 3cc of available fluid volume. We'll say a working QT function adds another 3cc of volume for a total of 6cc.

If the rears normal fluid requirement is 2.5 cc that's not a problem even for the broken MC. However when the clearance in the caliper increases, so does the amount of fluid needed to close the gap. Excess clearance can easily double the volume needed to close the calipers.

A broken MC is stuck with just 3cc. A working MC has 3cc(or likely more) to squeeze down to the calipers. The MC that's working right will suffer drom low pedal but the one with the bad valve will drop a very long way.