Soft brake pedel

[Dom2door]

When bleeding the ABS system I think the air go back through the master cylinder. I am going to check the master cylinder I pulled off to see if air is in it. I keep it full and plugged.

 

[Erik the Awful]

I think the problem is in the calipers after pinching the flex lines.

Nope. If you pinched the hoses and the pedal's still spongy, you've eliminated the calipers as a cause.

 

[Dom2door]

That's just it, with the hoses pinch the pedal is hard.

Pedal hard with tuck not running, soft when is, the only time it matters the most.

If the booster is keeping the master cylinder from going all the way back might be a problem, did not check that, not that I know how.
Just thinking out side the box
The junk always had this problem since I bought it, payed to much for it, hate it.

 

[DamHoodlum]

It takes alot of work to get ALL the air bled out.

I also have all new master cylinder, brake lines, calipers, rotors, pads, proportioning valve, hardware etc.....

My Brakes Work Perfect!!!!

 

[Dom2door]

Looking at the GM procedures I did all that just did not wait 15 sec between pressing the pedal down again. I did the low pressure bleeding and the two person bleeding at the same time and again did not wait 15 sec. I did get one pint out.
Back to the drawing board

 

[jaywestfall]

It takes alot of work to get ALL the air bled out.

I also have all new master cylinder, brake lines, calipers, rotors, pads, proportioning valve, hardware etc.....

My Brakes Work Perfect!!!!

Is that a set for a J5, and did you use a stock power booster?

 

[Schurkey]

Is that a set for a J5, and did you use a stock power booster?

J5? Do you mean JB5?

No, that is the WRONG master cylinder (it's a 2-chamber, should be a 3-chamber) for a vehicle with low-drag front calipers as would be included in the JN3 / JB5 / JB6 brake system.

But he says he's replaced the calipers. So maybe his truck doesn't have low-drag calipers any more. For all I know, his truck may not ever have had low-drag caliper--JB7, for example.

 

[kylenautique]

I have a 1999 two door Tahoe
I am sure this has been talked about, read all I could find on line but no real fixes.

I did replace all of the flex lines , calipers, pads, shoes, master cylinder and rear cylinders.

I bleed the system every witch way , presser, two person, pressure and two person, and reverse bleeding by pushing fluid up to the master cylinder. I also did bleed the ABS system via automatic bleeding.
I tracked it down to my calipers. I pinched off the flex lines an I get a good hard pedal this tells me that there is no air in the lines. I don't know what would cause this in my front calipers and the back could be a little out of adjustment.
Pedal gets better with just the back flex line pinched. Pinching the passenger front has more effect on the pedal then the driver side front. Could it be bad calipers?
Thanks for any help, Dom

Just fyi, there is no way to bleed the ABS system without a gm scan tool or snap on tool. If you got air in the system, that’s the only way to correct it. Make sure you bench bled your master cylinder first. If you did the NBS MC upgrade, it doesn’t

I have a 1999 two door Tahoe
I am sure this has been talked about, read all I could find on line but no real fixes.

I did replace all of the flex lines , calipers, pads, shoes, master cylinder and rear cylinders.

I bleed the system every witch way , presser, two person, pressure and two person, and reverse bleeding by pushing fluid up to the master cylinder. I also did bleed the ABS system via automatic bleeding.
I tracked it down to my calipers. I pinched off the flex lines an I get a good hard pedal this tells me that there is no air in the lines. I don't know what would cause this in my front calipers and the back could be a little out of adjustment.
Pedal gets better with just the back flex line pinched. Pinching the passenger front has more effect on the pedal then the driver side front. Could it be bad calipers?
Thanks for any help, Dom

I have a 1999 two door Tahoe
I am sure this has been talked about, read all I could find on line but no real fixes.

I did replace all of the flex lines , calipers, pads, shoes, master cylinder and rear cylinders.

I bleed the system every witch way , presser, two person, pressure and two person, and reverse bleeding by pushing fluid up to the master cylinder. I also did bleed the ABS system via automatic bleeding.
I tracked it down to my calipers. I pinched off the flex lines an I get a good hard pedal this tells me that there is no air in the lines. I don't know what would cause this in my front calipers and the back could be a little out of adjustment.
Pedal gets better with just the back flex line pinched. Pinching the passenger front has more effect on the pedal then the driver side front. Could it be bad calipers?
Thanks for any help, Dom

I have a 1999 two door Tahoe
I am sure this has been talked about, read all I could find on line but no real fixes.

I did replace all of the flex lines , calipers, pads, shoes, master cylinder and rear cylinders.

I bleed the system every witch way , presser, two person, pressure and two person, and reverse bleeding by pushing fluid up to the master cylinder. I also did bleed the ABS system via automatic bleeding.
I tracked it down to my calipers. I pinched off the flex lines an I get a good hard pedal this tells me that there is no air in the lines. I don't know what would cause this in my front calipers and the back could be a little out of adjustment.
Pedal gets better with just the back flex line pinched. Pinching the passenger front has more effect on the pedal then the driver side front. Could it be bad calipers?
Thanks for any help, Dom

If you got air into the ABS system you cannot bleed it without a GM scan tool or Snap-on scan tool. Make sure you bench bleed your master cylinder before installing. If you are doing the NBS master cylinder upgrade, it doesn’t always work with JB6 brake systems. If your rear brake shoes are way out of adjustment, that will also make your pedal have tons of travel.

 

[jaywestfall]

J5? Do you mean JB5?

No, that is the WRONG master cylinder (it's a 2-chamber, should be a 3-chamber) for a vehicle with low-drag front calipers as would be included in the JN3 / JB5 / JB6 brake system.

But he says he's replaced the calipers. So maybe his truck doesn't have low-drag calipers any more. For all I know, his truck may not ever have had low-drag caliper--JB7, for example.

Yes. JB5

 

[Dom2door]

My build sheet has JB5 brake system, when replacing parts that is what I went with, I don't have a snap on or a gm scan tool but do have a foxswell that can do automatic bleeding.
I did F up and probably got air in the ABS system, long story. Never had a good pedal so not sure if it had air in the abs system.

Going through the ABS functions on the FoxwellFoxwell, I used the dump funtion on both the front left then the right but could not get the rear to dump, no codes.

Up date
With the obs master cylinder back in I plugged the outlet ports and had a hard pedal, no move ment just the slack in between pedal and booster. Removed the smaller plug and reconnected the steel line, pedal travel down even with gas pedal. With brake lines hooked back up and another + gal of fluid bleeding with the ABS cycling, padle even with gas pedle. It stops.