Brake! Warning light on

[VIKING_MECHANIC]

Alright guys, need your help. I'm got a problem with the brakes on my 97 C1500 that mimics almost the same problem I had two years ago with it.

Back story:
A coworker was trying to help me figure out why my parking brake wasn't working properly, it would apply but wouldn't hold the truck. The cable to the left rear drum is very tight, while the cable on the right drum was loose. After some dicking around, I noticed the front cable is for a K3500 w/longbed(determined this with part number and went through my email to the day I bought it). The cable going from the pedal tp the middle of the frame is very tight, even with the pedal fully disengaged.

Now the problem. We thought we could disconnect the shoe from the plate the cable is attached to until I can get another cable. Put everything back together and now the brake pedal goes straight to the floor and the red brake light is on. Knowing what that light means, I immediately assumed air some how got in the system. We took off the drum and reconnected the brake cable and adjusted the shoes and put the drums back on.

Nothing changed.

I bled the brakes (twice) with our bleed machine and very little difference. I even tried bleeding the abs. Can use our scan tool because there is codes on and it refuses to do the procedures.

I even bled the abs manually and noticed a lot of air bubbles came out until it was a solid stream(even had coworker pump the pedal).

I don't remember what I did to correct this when it happened two years ago. Am I missing something? Keep bleeding brakes/abs module?

 

[Donald Mitchell]

Sounds confusing. How could the parking brake affect the hydraulic brakes?

 

[0xDEADBEEF]

Maybe the wheel cylinder popped because the shoe was gone and now it's seeing a loss of pressure tripping the light? I dunno.

 

[VIKING_MECHANIC]

Okay. I figured it out.

I bled the brakes again, this time manually with someone in the seat while I was under the truck with a bottle quarter full of brake fluid and a hose. Bled all four corners.

Pedal is firm and the brake light is off.

And my parking brake works now.

I don't know.

 

[Schurkey]

Verify BOTH adjustments--the service brakes at the two rear wheels, and AFTER the service brakes are adjusted properly, make sure the park brake is adjusted properly.

1500s almost always have the 254mm (10" leading-trailing shoe) drum brakes, they're "automatically" adjusted by using the park brake, and nobody uses the park brake. As a result, the shoes get way out of adjustment. If you're lucky, nobody has tightened the park brake cable to make-up for improperly-adjusted service brakes.