GMC Sierra C/K (Pre-1999):

Brake pedal fade

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#1 9/28/2017 8:10 PM

1717Kyle
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Registered: 9/28/2017
Posts: 2

Brake pedal fade

I have a 96 C-1500 that has brake pedal fade.New rear brake job including wheel cylinders, adjusted and working fine for 8-10 months. Brake pedal started fading, saw fluid leak from rear of master. Replaced master with reman one and could not get non fading pedal. Swapped out master, must have been a defect. Still have fade. Replaced with New master, still have fade. I was ASE certified in brakes in the late 90's. Now too old to deal, I brought it to reputable shop, installed new master, same thing.Shop owner says he is at a loss.......does anyone have an idea?    Thanks.

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#2 9/29/2017 8:49 AM

TechHelp2
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Registered: 11/23/2009
Posts: 1258

Re: Brake pedal fade

When you say fade do you mean the pedal is sinking or are you having trouble stopping (extra pressure on brake pedal to stop)?

Brake fade also relates to the brake system when the system over heats and you have trouble stopping. This can be fixed by replacing the brake fluid with DoT 4 fluid (higher boiling point). If the pedal sinks then it is a different story.

The other area to pay attention to is the flexible brake hoses. If they are old they can expand when you step on the brake causing the brake pedal to sink (fade). You can check this with a micrometer, measure the hose at a few points then have someone step on the brake hard and measure again and compare the two measurements. I don't remember how much is but if there is not much of a difference then it could still be air in the system.

The best way to get air out of the brake system is to take your truck to a repair shop that has a pressure bleeder. This will force any air out of the system and also replace old brake fluid with new fluid.


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#3 10/5/2017 6:03 PM

1717Kyle
New member
Registered: 9/28/2017
Posts: 2

Re: Brake pedal fade

Pedal goes to floor right from the get go, dash brake light never comes on. Hoses are fine, adjustment on rear is good. Have bled so much complete clear fluid thru out system. It acts like there is air in the system, but there isn't. I have seen other posts about other year models having simular issues and someone said something about the abs system having a valve or something that must be open to get all trapped air out???    Been through 5 master cylinders and a very complete system bleed, can't get pedal to stop going to floor. The first hit of the pedal works well it just continues to go to floor.

GMC Sierra C/K (Pre-1999) Recalls, TSBs and Service Information >> ALLDATA

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#4 10/6/2017 10:52 AM

TechHelp2
Administrator
Registered: 11/23/2009
Posts: 1258

Re: Brake pedal fade

You said the brake pedal goes to the floor and the brake light is not on. Does the light work?

Take a bottle and use hose that fits over the bleeder valve.

Partially fill the bottle and put the hose over the bleeder and insert the hose into the bottle.

Fill the master and put the cover on, open the right rear bleeder.

Open the bleeder and gently press the brake pedal about half way then release, have someone look for bubbles in the bottle. If you see bubbles in the bottle keep pressing the pedal until the bubbles go away. You have to check the master all the time to make sure it does not run dry. This may take a while and may use a lot of fluid, be patient after a while if no air is noticed move to the left rear wheel and do the same procedure. Then move to the right front wheel then the left front wheel.

You may have to crack the lines on the Electronic Brake Control Module (EBCM) to see if there is any air trapped inside the valve body as you press on the pedal.

If you can't get a pedal your only option may be a repair shop with a pressure bleeder to get the air out. The mechanic can also put a scanner on the vehicle computer to see if there are any brake codes stored in the computer.


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