Brakes don't always work

[white90gsx]

OK sometimes for no reason the back brakes don't seem to work and the brake pedal almost goes to the floor but then sometimes they work real good and are real stiff as soon as you press the brake pedal there's brake right away..This just started this maybe a week ago.

[bmoha2]

bleed your brakes

[white90gsx]

Yea I was going to do that this afternoon. But the problem only seems to happen after a few hard runs..

[bmoha2]

causing your brake pads to glaze. If that's your case, look at slotted or cross drilled rotors and higher quality brake pads. I had definitively done a few hard braking runs in the past and when the brakes got to hot, had nothing, nada. Scary as all hell. If your rotors are too thin, worn out they make not be able to retain enough heat and become useless. I went to slotted rotors and virtually eliminated the problem. That is of course assuming that you don't have any actual mechanical brake system failure. I mean leaking brake lines, leaking brake calipers etc. Check the fluid in your brake fluid reservoir. If it is lower after you lose your brakes you're losing brake fluid somewhere. When I first installed my SS brake fluid lines, I experienced exactly that. Turns out I needs a couple more turns on one of my brake lines.

[white90gsx]

Yea my rotors need cut anyways I was just going to buy the cd and slotted anyways but now that you mention by back rotors are really thin.

[Rob10_99]

Being a perf. autotech, I would suggest you never, ever cut your brakes.
You want as much metal on your disc's as you can get, and as much cooling as you can get.
Ducting and drilled/slotted with some good pads will make your brakes almost 2x better than stock dsm garbage.
Get SS lines for sure, and do your clutch line while your getting dirty!

Just an FYI, cutting your brakes is only about $20 cheaper than buying new rotors, IMO, go with rotora slotted and or slotted/drilled with the SS lines.

[snowborder714]

I would highly suggest staying away from cross drilled rotors as they usually are not cast with the holes drilled, which makes them more prone to cracking. The PowerSlot slotted rotors are very nice if you have to have slots. If not, get Napa blanks, which work perfectly fine. And then get a good set of pads, some decent fluid, and SS lines.

And if you really want to get fancy, get SpeedBleeder bleeder valves

[bmoha2]

speedbleeders are mandatory! They rock!

[DSM Jeff]

I'm curious as to how you know the rear brakes aren't working? I would say bleed all the brakes but if this doesn't fix your problem I would look into an issue with the master cylinder.

[white90gsx]

Yea its weird an even when I do bleed them I wont know for days because sometime they dont stop working for a couple days. They will stop for a hour or two then work fine..

[DSM Jeff]

Originally Posted by white90gsx

Yea its weird an even when I do bleed them I wont know for days because sometime they dont stop working for a couple days. They will stop for a hour or two then work fine..

Are you loosing any brake fluid? You could have a seal going inside the master, allowing pressure to bypass where it is suppose to go.

[bmoha2]

First and foremost check to see if you are losing any fluid. If you are identify where you're losing it. Start eliminating the possibilities one at a time until you find your problem. A lot of people have a hard time feeling whether their rear brakes are doing anything or not. Some people just aren't sensitive like that. I don't think I ever really felt my rear brakes until I upgraded the rear rotors to Powerstop cadnium coated crossdrilled rotors with EBC Kevlar Green brake pads and a set of SS brake lines on all four corners. Of course I also put slotted Brembo rotors on the front with the same brake pads at the same time. Before, the front brakes were doing all the work. Not only that but when I tore everything apart to replace the rear rotors I found out that the rear brakes pads had worn in a really bizarre way and were only actually grabbing with about a 1/3rd of an inch of the whole brake pad. If you really want your brakes to function and feel like you want them to, you have to get us a little more information and be willing to start taking a few things apart to see whats going on. You need to take out and clean and relube the two brake caliper slider bolts on each side of the rear. If they look rusted or corroded with pitting, it is time to replace them. they are pretty cheap from the dealer. Does your brake pedal feel spongy? Sometimes if you have one of the slider bolts seized it will produce a spongy feeling pedal. I had a seized slider bolt on each side of my front brake calipers. Hella spongy feeling pedal. Bleeding your brakes wont help that. You need to make sure that first off your brake rotors aren't worn too thin to be able to deal with heat. If they are too thin they will overheat way too fast. If they are replace them. Are your brake pads worn out? If so replace them. Do your brake pads slide freely in the brass retainer clips? If they don't you may need to do a bit of filing to get them to move freely. Don't count on brand new brake pads being a perfect size. I have had to file every single one of my brand new EBC pads. I have done the same with other brands as well. You are looking to remove sources of stiction from your brake system. If the brass clips look bent or damaged. Replace them. Some people replace them every time they replace their brake pads. Look at your bleeder screws to see if they are leaking. Look at the bolt where your brake line attaches to the caliper t see if they are leaking. Look at the spot on the inner fender well where your brake line is connected to the hard steel line for leaking. Leaking is bad.

[white90gsx]

No im not losing any fluid anywere..The petal is not spongy it just goes more to the floor for the brakes even to engage and when they do I can feel them hitting rock bottom and my front tire almost lock up..But it hasn't done it in 2 days..Pads are like 50% in rear still.

[havoc742]

I had the same problem in a 91 S10. Took it to 2 different shops for an inspection and both (Brake Masters, Les Schwab) confirmed my front end was about to drop out the bottom of the truck. Bushings were shot in the entire front end. That's what I get for driving it like I stole it for 6 months.

[bmoha2]

They might be too thin to be doing anything good. If your rotors are half as thin as they should be and your brake pads are 50% worn out, it still wont work so well.

[white90gsx]

That's what I thought from day one because my rotors are pretty thin in the rear but why only do it once in a while?

[bmoha2]

the thinner they are, the less they can deal with the heat. When they get too hot they lose grip. If you are saying that they only fade when you are doing a few harder stops. Maybe you need to see if you have a seized caliper.

[bomper04]

if you have checked to see that their is no contaminants in your brake fluid and have bled your entire brake system then it's time to check the master cyl. most likely it's your primary cup seal...well at least to my knowing. i might not know much =(

[Bud92gsx]

I don't want you to drive on them hard, but I had a seized caliper twice now. Both on the front, not same wheel either. But that made one of my wheels really hot. Now Go to advance auto get new rotors on the rear, a quart of DOT 4. bleed out completly, fill with DOT 4, after installing rotors of course.

[Bud92gsx]

Originally Posted by bmoha2

They might be too thin to be doing anything good. If your rotors are half as thin as they should be and your brake pads are 50% worn out, it still wont work so well.

Get ceramic pads as well. Saved my life a couple of times...