brakes problem

[trx88]

my buddy has a 91z71

its of course got disk in front drum in back

hes recently had a problem with his fluid leaking out at the master cylinder under the resivour

we replaced the two grommets that go under there and fixed that problem

then today we bled the lines and put all new fluid in there and bled the lines right

and bled each wheel in order multiple times repeating the whole truck three times

i am sure that the lines have no air and are full of fresh fluid

the brake pedal is still soft once he starts the truck

and it makes a real loud whissh sound as he steps on the pedal

im not sure whats wrong with it

possibly in need of a master cylinder rebuild? or possibly the booster?

any ideas friends id be grateful!

 

[6chevy9]

sounds like its still leaking somwhere IMO. anything overlooked? in hurry doing it? the simplest things can be forgot man.

 

[Hodges87]

This is how I always bleed the lines:

1. Pop the hood and remove the cover to the master cylinder and top it off with brake fluid.

2. Start at the Pass-Rear wheel, and crack the bleeder valve and leave it open, but not open all the way. Do not press the brakes or start the vehicle!

3. Take a 10 minute break and be sure to check the brake fluid level in the master cylinder, refill if necessary.

4. After about 20 minutes, inspect the amount of brake fluid leaking from the bleeder valve, if its flowing good close the valve. If not then give it a little more time.

5. Repeat the steps with the remaining wheels in the following order: Pass-Rear, Driver-Rear, Pass-Front, Driver-Front

Hope this helps!

 

[nedla1alden]

Don't know if this helps, but I had same hissing problem on my 97, soft pedal and air hissing sound. Brake Booster was bad.

 

[tattooed4life]

This is how I always bleed the lines:

1. Pop the hood and remove the cover to the master cylinder and top it off with brake fluid.

2. Start at the Pass-Rear wheel, and crack the bleeder valve and leave it open, but not open all the way. Do not press the brakes or start the vehicle!

3. Take a 10 minute break and be sure to check the brake fluid level in the master cylinder, refill if necessary.

4. After about 20 minutes, inspect the amount of brake fluid leaking from the bleeder valve, if its flowing good close the valve. If not then give it a little more time.

5. Repeat the steps with the remaining wheels in the following order: Pass-Rear, Driver-Rear, Pass-Front, Driver-Front

Hope this helps!

Or try how I do it--it will require 2 people.

1-Top off master cylinder.
2-Start at pass. rear wheel, have a person in the car start it and pump the brakes several times and hold the pedal depressed at the same time you crack the bleed screw until the pedal goes all the way to the floor. IMPORTANT-Don't let the pedal up until you tighten the bleed screw. If you do it will draw air back in and defeat the purpose of bleeding the brakes.Have helper pump up the brakes and hold again, crack bleed screw and repeat earlier steps. Do this until a steady stream of fluid comes out.
3-Top master cylinder off
4-Move on to rear drivers wheel and repeat step 2
5-Repeat step 3
6-Move on to pass. front wheel and repeat step 2
7-Repeat step 3
8-Move on to drivers front wheel and repeat step 2
9-Top off master cylinder and pump brakes. Check for firmness in the pedal and that it doesn't surge of "drop"-air in lines. Also while pumping the pedal, you or your helping should check all the bleed screws and make sure they are not leaking and tight.

 

[hiredgun8]

Or try how I do it--it will require 2 people.

1-Top off master cylinder.
2-Start at pass. rear wheel, have a person in the car start it and pump the brakes several times and hold the pedal depressed at the same time you crack the bleed screw until the pedal goes all the way to the floor. IMPORTANT-Don't let the pedal up until you tighten the bleed screw. If you do it will draw air back in and defeat the purpose of bleeding the brakes.Have helper pump up the brakes and hold again, crack bleed screw and repeat earlier steps. Do this until a steady stream of fluid comes out.
3-Top master cylinder off
4-Move on to rear drivers wheel and repeat step 2
5-Repeat step 3
6-Move on to pass. front wheel and repeat step 2
7-Repeat step 3
8-Move on to drivers front wheel and repeat step 2
9-Top off master cylinder and pump brakes. Check for firmness in the pedal and that it doesn't surge of "drop"-air in lines. Also while pumping the pedal, you or your helping should check all the bleed screws and make sure they are not leaking and tight.

This
Same way I was taught years ago.

 

[Butch]

This
Same way I was taught years ago.

same here, bleeding brakes is a pain in the ass but a nessary evil.

 

[Mike]

You have air somewhere. If it comes to it, look up bench bleeding a master cylinder.

 

[sandifer01]

trx88. It is the brake booster. I had the exact same problem in my 95 ecsb. I bought a new booster and installed it. Fixed the problem.

 

[Swims350]

I bleed the 2 person way as above but not with it running.