bad brake problems, need some input before i start troubleshooting

[Jagged]

I would appreciate any input and ideas before I start troubleshooting tomorrow afternoon:

I just recently put some larger tires on the truck, from 31x10.50 AT's to 32x11.50 mud rover's. My brakes have since disappeared, before I put the new tires on they were getting a little spongy (if that's a correct term). But today I had to stop from 60 MPH and it took me well over 200 yards to do so with the pedal to the floor (ended up having to downshift the tranny to help stop it). The Brake idiot light is on constantly now, I have fluid in my master cylinder (although it's kind of black looking). The rubber part of the brake lines don't expand when the pedal is pressed. The past few weeks both the discs and the drum brakes have been squealing rather loudly as well.

This is on an 87 K5, 350 TBI / 700R4 (vaccuum brake booster I believe), and if it makes any difference, the 350 has a Comp Cam 270H running in it with stock ratio rockers.

My current ideas are; check the vaccuum lines, and brake lines for leaks and inspect my pads/drums/rotors. Anything to do with the master cylinder or booster I really have no clue about.

Brakes really aren't my forte, so once again, any input would be greatly appreciated.

 

[1-ton]

Adjust your rear brakes.

(edit) Like the other guys said "Master Cylinder".

 

[tunedportk5]

I think I would try replacing the master cylinder, thats what it sounds like to me. I forget what problem sets off the brake light on the dash besides the E-brake

 

[k5freak44]

master cylinder sets off the brake light.

also if the brakes are compressed to far the light will go off. this hapend when my pads were worn down to nothing

 

[tunedportk5]

What condition are your pads in, and does the E-brake work

 

[spearchucker]

Sounds like you need new shoes and pads, that's why it's squealing and hard to stop. Replace those and see how much it improves before you try anything else. And it also sounds like you need to flush some new fluid through the system.

 

[Jagged]

Unless I've somehow killed my pads this past two weeks they should still be good; they were well within wear limits when I mounted my new tires. I just picked up some brake fluid today and a friend of mine who used to work brakes a lot are gonna flush out the system and go from there. I'll just start with the cheap, easy part first and move on up... hopefully flushing out the system will work, but I'll definately check my pads and rotors again (and the seals around the pistons).

 

[rusty79beast]

I've had my idiot light come on two times for two different reasons. First was on my 79 Blaze. The culprit was in fact a leaking rear brake line. Once I fixed that the light went off and all was well. The next time I had the idiot light come on was on my 86 Blaze. When I would try to stop a little harder than normal the idiot light would come on and I could tell that it took longer to stop! I could get the light to come off if I was stopped, and put the brake pedal all the way to the floor. I then replaced the rear shoes I believe and the problem was solved. I had replaced the front pads about 5 months prior. I hope this helps. Good luck

Paul

 

[Blue85]

The idiot light means there is an imbalance in pressure between the front and rear circuits.

Based on how bad you say it is, my first guess would be that you have a leak somewhere.

 

[Zeitler]

maybe i'm stupid , but i don't see how old brake fluid can cause poor brakes?

although i've heard that it picks upp water or something over the years

 

[Jagged]

Well, we seem to have fixed the problem. Replace the rear brake shoes and wheel cylinders (both had leaking seals). And we also flushed/bled the brake system. My rear driver's side had a whole lot of air in it.

 

[spearchucker]

maybe i'm stupid , but i don't see how old brake fluid can cause poor brakes?

although i've heard that it picks upp water or something over the years

I never said that his old fluid was the cause of his poor braking. But in his original post he stated that the brake fluid in the resevoir was black which means it's contaminated, it should be redish.