Brake's won't work Help

[Thumperbr549honcho]

Ok, I have alright pressure to the rear brakes but is not sending hardly any pressure/Fluid to the front brakes. I put new show and pads in a few week ago. I can mask the petal all the way to the floor some of the time. part of the time I can make it nose dive then some of the time the flippen thing won't stop at all. I have bleed the system the best it will let me. It doesn't let me.

[lkmarsh]

How old is the master cylinder? A brake system that works one second but not the next usually means the master cylinder needs replacement. Does pumping the pedal help at all? Does a quick stomp work, when a slow steady pressure bottoms out? All signs of MC failure. Bleeding the brakes by yourself or do you have a helper? My most frequent mistake was forgetting to refill the mc.

[HOOT]

Did you push in the pin on the proportioning valve?
If not then get a clamp and something to clamp in there to push it in while you bleed your brakes.

If you've done that then start looking for leaks. Pull the drums to check inside.

If all that looks OK then you might have a bad master cylinder.

The rubber seals and rings in these systems go out after a while and most of them are way past their prime.

I'm currently replacing everything from power booster to the rear wheels which are getting upgraded to disc while I'm at it. Only old part will be my proportioning valve. It may get replaced before it is all done, I just forgot to order one and I never hear of those failing..

[HOOT]

Brake System Maintenance


Contributed By: Joe Sego
I won't bother you with another how-to on replacing brake pads or shoes. Want I want to address is the need for brake fluid replacement. IMHO this should be done every two years or so.
This task is seldom done on vehicles, but, it's very important. Yeah I know "my brake system has 220k miles on it and it's fine" well I say you are lucky. The brake system is very prone to absorbing moisture. Moisture is the #1 killer of calipers and lines, not to mention the master cylinder.
Brake fluid absorbs moisture. Ever wonder why your fluid looks different shades of brown? *Water* i.e. moisture has caused rust in your system and contaminated the fluid. Quality brake fluid is clear or slightly off color.
Changing the system of all it's fluid is easier than you might think. Several methods work well. I'll not cover the vacuum pump method which draws in new fluid as the old is removed. My preference is the easiest method but takes a bit of time and you can do it alone! No need to have someone pumping the peddle and all that. let's use gravity to change that fluid!
"What type of fluid should I use?" There are several choices, many swear by the 100% silicone fluids. Silicone brake fluid will not absorb moisture as fast as DOT 3, but many complain of a soft peddle with silicone. I would suggest using what your Owner's Manual suggests. Most likely DOT 3. Very cheap too. Depending on your vehicle I would start out with a couple quarts.
The tools you'll need are few. Here is a sample;

• Jack stands ( don't cut corners here!)
• Good floor jack (dittos)
• Brake fluid
• Six point socket for bleeders valves
• Short length of rubber hose to fit bleeder nipples.
• Container to catch old fluid

Be extra careful with brake fluid as it will remove paint!
The gravity method is the (imho) the simplest and safest method to change your brake fluid. I also use the gravity method to bleed my brake systems.

1. Jack up the truck and use jack stands.
2. Remove the wheel(s) not mandatory but easier.
3. Start at longest brake line and work towards shortest; right rear, left rear, right front, left front, in that order.
4. Loosen the bleeder valve and attach the rubber hose to it and put other end of hose in a container. The fluid should start to flow.
5. At the master cylinder add some fluid as necessary to the rear half of reservoir. Do not pump brake peddle. Let fluid flow until it runs clear. (remember to keep adding fluid to master cylinder as needed)
6. This process takes a bit of time, but, you will end up with an 'airless' brake system, plus you can do this alone.
7. Do not move to the next wheel until the fluid runs clear at the current wheel. You'll have time to do other maintenance while the brake fluid flows!

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[Thumperbr549honcho]

How old is the master cylinder? A brake system that works one second but not the next usually means the master cylinder needs replacement. Does pumping the pedal help at all? Does a quick stomp work, when a slow steady pressure bottoms out? All signs of MC failure. Bleeding the brakes by yourself or do you have a helper? My most frequent mistake was forgetting to refill the mc.

Not Sure probly the original. Pumping pedal results in pedal all the way to the floor light bright and no brakes. When I do a quick stomp it works for the first pump I take a nose dive but it goes to the floor by the 2nd or 3rd pump. This results in no stopping power, but the drivers rear wheel will lock up occasionally.

[Chevelleguy]

Sounds like the cups are hard and not sealing in the master cylinder. Replace the master.