brake warning light/brakes question

[GER]

On my '80 GMC Heavy-Half, does the brake warning light mean the rear brakes are out of adjustment, or is it a master cylinder or booster issue? Or something else? This is the light that comes on when you put the emergency brake on, but even with the e-brake off, the light just stays on. The light came on occasionally before and I noticed the brakes were getting a bit 'mushy'. I have since replaced the master cylinder, and before that the front calipers,pads,and had the rotors turned. The rear brake shoes looked like they had lots of material left.
I tried bleeding the brakes at all four corners with a mity-vac, but now the light still stays on and the brakes are not very strong right now. I am thinking the brake system may still need some bleeding, but I am now wondering if there may be additional parts I have to replace. What do you guys think?
Thanks for your help!
-Gerald.

 

[58 chevy]

RE: brake warning light/brakes ques

It may be that the pedal isn't coming all the way back up, which is keeping the light on.

 

[GER]

RE: brake warning light/brakes ques

I've checked the e-brake pedal and it is all the way up. That was the first thing I checked. The light started coming on occasionally while I was driving, and at the same time, I noticed that the brakes were starting to feel weak. I thought that maybe the two symptoms were related, and that the park brake light was also a warning light that there is something wrong in the system? Maybe not?

 

[83silverado]

RE: brake warning light/brakes ques

This is actually common in older chevys. The only reason your brake light will come on besides your e-brake is from pressure variances in the system, picked up by your prop-valve. It is located on the front most cross member on the rear side of it. it is possible that it may need replacement, but you probably just need to rebleed your system. Use a partner and do an up down procedure.(open valve, push peddle down, close valve, let peddle up). Dont pump the brakes because it just stirs the the fluid around and may actually cause air to stay trapped in certain areas. I hope this helps, I've ran into this problem many times.

 

[GER]

RE: brake warning light/brakes ques

Thank you so much Silverado! I knew that light was to do with something else in the system too. I will try and rebleed the system again when i get a chance (truck's outside and it snowed again!) and I will let ya know how I made out. Thanks!
-Gerald.