This is on my 81 Blazer Ok so i noticed today my brakes got harder but still worked alright so i checked to make sure the vac line was still hooked up and not clogged and it was good. So then on the way home i tried hitting the brakes hard to make sure they still work in case of an emergency and they got 20 times worst. no i barely have brake and it's still really hard to push. When i push the brake and hold it you can here it going psss where it goes into the master cylinder. I've had master cylinders go out of other cars many times and when they did the pedal went to the floor thats why im confused about this. i don't have a leak anywhere either or the pedal would go to the floor.

 

Before replacing a master cylinder, try bleeding out the brakes starting on the passenger rear to drivers rear to passenger front to drivers front. Don't forget to check the brake fluid level every few times you pump up the brakes.

 

ok i just tried to bleed them and the rears bled ok but the fronts wont at all, i open the valve and nothing happens. what coudl it be?

 

Nobody's ever had this problem eh?

 

With bleeding the brakes, you may have pushed the pedal down to far and triggered the equalizer valve to shift.
Sometimes you can get it back to center by giving the brake pedal a quick hard push (almost like a kick).

The idea of the valve (which is a block that the brake lines from the master cylinder go in to before the lines are directed to the wheels), is that if a brake line breaks on the front, you will still have rear brakes. If a rear line brakes, you still have front brakes.

On the equalizer valve, there is a pin on the top, covered by a rubber boot. If you open the front bleeder screw, hold the pin down and have someone push the brake pedal. You should be able to bleed the front brakes.
If that doesn't center the valve, try kicking the brake pedal again. They can be tough. I have sometimes had to replace the valve if they don't equalize.

From reading your post, I thought that your original problem was not a bleeding problem, but a booster problem. Is the hissing you hear air (vacuum)? If you hold your foot on the brake pedal, than start your engine, you should feel the brake pedal go down a little. That shows you that the power assist from the booster is working.

Post again if you need more help. Post again when you figure it out. I always like to hear the results to know if we're right or wrong with our long distance diagnosis.

 

When i have my foot on the pedal and turn in on it does nothing, as i know it should shift down a little bit. It actually was a little stiffer on the top of the breaks earlier today and when i kinda slammed on the brakes to make sure they were still workign fully was when it suddenly got REALLT stiff and just about no brakes. I checked the vacume line to the booster and it's all good.

 

I'm sure the vacuum line to the booster is fine but, you said that when you push on the brake pedal, you hear it "going psss "
That could be an internal vacuum leak in the brake power booster.
There is a rubber diaphram in the middle of the booster. If it tears or has a leak then there will be no assist and the vacuum will go right thru the booster, probably to the vent in the back ( which is actually at the prake pedal rod, inside the truck behind a rubber boot.)

Let me know if you don't understand, and I will try to find and post a picture.

Keep asking questions, and you will find the solution.

 

i understand what your saying. But i still don't get why my front brakes can't bleed. I know that the problem isn't air in the line but still. So do you say i go ahead and replace the booster?

 

What I was saying is that I think your original problem was NOT air in the lines. I don't think you needed to bleed the brakes. If you had air in the lines, you would have avery soft brake pedal, that might go to the floor if you stepped on it hard.
Now that you bled the rear brakes, you have created a problem with the equalizer valve.

If you hear a hissing noise while stepping on the brake pedal, it probably is a power booster problem. That was your first problem.
Try to locate the hissing noise. Start the engine. Put youe ear clse to the brake pedal. Push the brake pedal with your hand and see if you can hear the hissing noise near the firewall where the brake pedal rod goes thru to the power booster.

I'll try to find some picture and post them. Pictures are always easier to understand.

 

yeah i know it's not air in the lines. And the hissing is right where the rod goes into the booster.