Well this is still a problem got the drum brakes adjusted out enough now that the ebrake works. no nice little oval punchout to get to the adjuster screw had to take the drums right off. But I still have a brake light on and the brakes are not good. I have tried to read the book on this and as far as I can tell it is the combination valve that is causing the light to come on. The book explains how to bleed them holding a pin in on it???
My 1991 service manual says these are your options:
1: malfunctioning caliper assembly.
2: malfunctioning master cylinder
3: contaminated or improper brake fluid
4: parking brake on or not fully released (I need to lift mine up with my foot after I use it)
5: worn out brake lining
6: incorrect wheel bearing adjustment'
7: malfunctioning self adjusters
8: brake assembly attachments missing or loose
9: improperly adjusted master cylinder pushrod
10: RWAL system malfunction (rear wheel anti-lock brakes)
Glancing through the manual, I think your problem is actually somewhere in your front brake system. When you have someone step on the brake, do you see those pin(s) moving? Yes? Then it's basically good... In that event, then my best guess is that your rear brakes are working (which wont stop your truck for shit) and that your front brakes ARE working. The proportioning valve in our trucks separates the front/rears not each corner. So poke around for some leaks or what not in the front braking system. See if your pads aren't worn to shit, no leaks, pinched or collapsed flex lines... etc. I've got GM's service manual in my lap, so if that doesn't help!
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