Brakes go to the floor :(

[Raspi454]

97 k1500 350 jb5
Bought the truck with brake problems thinking it'd be something simple. Pedal goes to the floor then has like an inch of actual brakes. Don't see any line leaks, bled them, replaced a wheel cylinder made sure the drums were tight, and they got good life in em still. Truck did include a new master cylinder, but seller's description of brake problem was very vague "needs brake work soon". What do you guys think? Should I put that new master cylinder on, or does it sound like something else?

 

[Pinger]

Does the pedal go straight to the floor or is it a slower sinking? If the latter, when stationary, and holding it on the brakes, does the pedal feel as if it's being pulled from under your foot?

 

[Raspi454]

Does the pedal go straight to the floor or is it a slower sinking? If the latter, when stationary, and holding it on the brakes, does the pedal feel as if it's being pulled from under your foot?

It goes pretty much right down then the last bottom inch of so is where the brakes start.

 

[Pinger]

For as long as the master cylinder is suspect you are probably going to have to replace it - though doing that didn't immediately cure my (slowly) sinking pedal.
What did was, getting some air out of the ABS unit, or replacing the rear flexible hose, or more thorough (rear) bleeding, or some combination of that lot.

If you haven't yet bled the ABS unit and you have the scantool to do it - probably better you do that first.

 

[Schurkey]

If you haven't yet bled the ABS unit and you have the scantool to do it - probably better you do that first.

Yup.

 

[Raspi454]

For as long as the master cylinder is suspect you are probably going to have to replace it - though doing that didn't immediately cure my (slowly) sinking pedal.
What did was, getting some air out of the ABS unit, or replacing the rear flexible hose, or more thorough (rear) bleeding, or some combination of that lot.

If you haven't yet bled the ABS unit and you have the scantool to do it - probably better you do that first.

I need a scan tool to bleed lines?! oh lord, anyway else I can do that?

 

[Schurkey]

You need a scan tool to bleed the ABS. If the ABS doesn't get air in it during the repair, you should be OK (assuming it doesn't have air in it NOW.

Considering that the brake pedal acts like the system has air in it--pedal is low and squishy--bleeding the ABS is probably going to be unavoidable.

If you bleed the ABS first, you may find that was the only "repair" you actually needed. Or--maybe not. Won't know until you try.

 

[Vanishing Point]

I'm afraid my colleagues are correct regarding ABS bleeding. And Harbor Freight does sell its $159.97 ZURICH ZR13 OBDII CODE READER with an ABS/SRS FIX ASSIST handheld scanner for Chevy/GMC Trucks that will help you accomplish all that with directions and prompts—again, depending on your experience and, of course, with some help.

 

[thegawd]

Schurkey living out in the country and having a long lane way I cycle the abs by slamming on the brakes. I do this a few times a year. I believe this exercise helps keep it good but the one time I needed to cycle the abs and I didnt have the scanner. I downloaded and paid for a couple apps that are supposedly able to perform the task but I just got pissed trying to figure it out. I jumped in the truck and cycled it many times by slamming on the brakes and then went back and rebled everything. I know this is not the ideal procedure but if one can do this safely, like on a farm and not a public road, how do you feel about it?

Al

 

[Supercharged111]

I threw my ABS in the dumpster, makes bleeding a snap.