Low Pedal Goes to Floor, Soft Brakes

Tiny
ESDLS
  • 1996 CHEVROLET TRUCK

Brakes problem HD K2500, Silverado, ABS Brakes, Vacumm Assisted Power Brakes.

I had good brakes firm pedal, pedal only moved about 1/3 distance to floor to attain firm solid braking action.

Then-- inspected front disk brake pads, needed replacement. Removed wheels, depressed brake caliper pistons, removed calipers, replaced disk pads, reinstalled calipers and wheels and started the truck, actuated brake several times to reset disc pads,

Now I have soft pedal, low pedal, pedal would travel all the way to the floor with steady foot pressure.
Replaced master cylinder, bench bled master cylinder, bled front brakes did the THING! ---

Thought new master cylinder might be bad, took new master cylinder back to parts store, exchanged master cylinder for ANOTHER NEW MASTER CYLINDER-- bench bled new master cylinder, put the second new master cylinder on truck, bled front brakes, started truck, tried brakes SAME DAMN THING, had soft pedal, low pedal, pedal would travel all the way to the floor with steady foot pressure. ----

While both new master cylinders were installed on the truck, removed cap from master cylinder, stepped on brake pedal, brake fluid squirted like a fountain out of the reservoir neared the winshield on both new master cylinders, even after the master cylinder secondary piston moved past the fluid inlet hole located in the reservoir. What the hell has happened to the master cylinders?---I do not know if the truck is even safe to drive with the soft pedal, low pedal, pedal that travels all the way to the floor with steady foot pressure.----

Please help-- do you have any ideas what might have happend? ----

Thanks Bob Zinter, Aurora, CO.

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Wednesday, August 27th, 2008 AT 9:24 PM

3 Replies

Tiny
MHPAUTOS
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Hi there,

Thank you for the donation,

I would get hold of 3 vise grips and clamp off all the flexible brake hoses, see how the pedal is then, if it is high and hard the problem will be in one of the brakes, do this test first.

Mark (mhpautos)

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Wednesday, August 27th, 2008 AT 11:03 PM
Tiny
ESDLS
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See my previous/first email to you---

Dear Mark (mhpautos), Certified 2CarPros Master Technician:

I have suspected that the ABS might be the problem, as when I first bought the truck I had the same proplem, but after I changed the Master Cylinder the problem went away.-- The problem that the truck had when I first bought it was as follows----
Soft Brake Pedal, very weak braking power, excessive pedal travel. One day when I was driving the truck on an icy road and had to stop the front wheels began to slip on the ice and the ABS kicked in--after the truck stopped and the red light turned green, I drove to the next red light and when I stepped on the brake-- the brakes worked absolutely perfect-- very little pedal travel, firm brakes pedal, the truck stopped better than it ever did. Then for no reason at all the brakes would go back to soft pedal and excessive pedal travel again-- so I would find an icy patch of road and intentionally skid the front wheels to activate the ABS and most of the time the brakes would begin to work perfectly again. This went on for about a month, then it stopped and never happened again for about a year, until last week whene I changed the front disk brake pads and it began again.--- Does this additional info provide you with any additional clues on what might be happening to my truck braking system?-- See my last/first Email to you.----Thanks, Bob Zinter

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Thursday, August 28th, 2008 AT 12:53 PM
Tiny
2CARPROS KEN
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This sounds like the ABS module is having a problem, I would have a shop with a tech2 open the valves and have the system power bled, this should remove the air in the system.

When you set the pads did you push down and let up slowly? if not the system is full of air due to the small orifice in the master cylinder. Here is a guide and video on how to do it correctly.

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

And how to bleed the system

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

Let us know how it goes so it will help others

Best, Ken

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Thursday, September 1st, 2016 AT 5:48 PM

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