Excessive brake pedal travel

[Case 7230]

Hi there. This is my first post here.
A couple of months ago I bought my first Chevy truck, a `92 K1500 with the 350 and 4x4 auto. The brakes would brake the truck to a stop with just a couple of inches of pedal travel but press just a little harder on the pedal and it would go to within a couple of inches of the floor. So I replaced front pads, rear shoes, then the master cylinder and rear wheel cylinders. The front flex hoses had been recently replaced so I replaced the rear one. I have bled it every which you can and nothing has changed it from when I got it. Any ideas? Thanks in advance.

[ryiguy]

Mine is doing same i've changed all as well mines a 89 Just brought a new master cylinder for it, hoping that will do it

[436'd skylark]

are the rear brakes adjusted snug?

[crabtruck]

I can never be sure what folks mean when they say they bled extensively, after having been fooled before myself.
It's essentially a closed system, you push on one end of a hose and the fluid tries to come out the other end.
Once no more can get out (brake shoes moved as far as they're going) you can not push more in from top.
Unless somthings bad or your being misled.

First something bad is the easiest to find: the fluid is leaking out.
You can see it, may have to pull wheels or you notice a drop in the resv.
Secondly, hoses may be expanding to take more fluid.
Third, you may be compressing air in the system. Usually pedal pumps will be a tip off.

You could be misled into thinking you're pushing more fluid
when seals in the master leak at the higher pressure.
Could try plugging the master ports and see if you get the same pedal action.

[Case 7230]

Thanks for the replies. Rear shoes are fully adjusted out. New flex hoses, new master cylinder, new rear wheel cllinders. Nothing I have done has made any difference to the pedal travel over when I bought it. With no booster (engine off) the pedal is high and hard except that with a lot of pressure on the pedal there is slight "give" in the pedal. Start engine and the pedal is easily pressed to within about a couple of inches of the floor. Yet when moving brakes very efective with just a couple of inches of pedal travel. When M/C outlets blocked then super pedal. Pumping pedal does not improve it. Any further thoughts?

[shoman44]

do u have abs?

[shoman44]

did u bleed the master after you put it on?

[shoman44]

Brake Pressure Modulator Valve (BPMV) must be bled just found it on my website for work.
It says that it has to be bleed if you do any service to the brakes such as master,caliper,cylinders or lines. So i am guessing that is what is giving u the low pedal . Good luck

[Case 7230]

Thanks shoman. Where is it and how do I bleed it?

[shoman44]

you will need these things to do the job if u have them or no somebody who has the tools.

Combination Valve Pressure Bleeding Tool (Three Required)
Tech-1 Scan Tool
RWAL/4WAL Cartridge Kit

i would send u a pic of what it looks like if u give me a email i can send pics to.
that is the problem with newer vehicle's its not like the good ole days where u just bleed the system and be done with it. The new electronics in these vehicles are so advanced , that now u have to hook a computer up to the vehicle's and tell them u are going to bleed them. for your year truck its not that bad once u have done one . but for the first time u will learn some things.... that is why i don't buy new i know how to work on them but is much more pain in the *** then anything else.