I have a 1988 chevy s-10 blazer i got for 200 bucks and im rebuilding it. It started with no brakes whats so ever. I replaced pretty much all the lines, the front has brand new calipers and pads and the back has brand new shoes, cylinders, and springs. I test drove it a couple times and the front brakes are engaged. I let off the gas and it slows down fast. I pulled back into my drive way and the front brakes has smoke pouring out. Someone told me maybe a porportioning value. Please help

 

Proportioning valve splits the pressure front to back like 70/30. If it failed I think you would have 50/50 split, or no proportioning of pressure as a failsafe.

I am wondering if there is a leak in the brake booster that is causing it to stay applied some? There is a little valve that opens when you step on the brake and uses engine vacuum to power assist your foots input. If that little valve is leaking allowing vacuum to leak in and apply some input force, it could cause your problem. You may be able to hear it hissing a little when your engine is on. Also, have you cracked a front bleeder with the engine on? Does it just leak or spray out like there is some force in the lines?

When the engine is off and you press the brakes and let off, can you spin the front hub by hand? Or is the brake staying applied even with the engine off?

 

I have not cracked the bleeder with the engine on, i did to bleed the brakes in the beginning and the flow was good. With the engine off, the brakes are still applied.

 

there must be a problem with the master cylinder if pressure is staying in the system when the engines off and pedal is not applied. When you lilft off the brake the pistons move inside the master and allow the fluid to pass back into the resevoir. Somethings not letting the pressure back in. Maybe there is a failed cup seal inside of it?

 

ok, i just put a brand new master cylinder in and the same problem is there. its not as bad, maybe because i didnt drive it as long, but the front brakes are still engaged, please help

 

Did you replace the rubber flex lines?

 

what do u mean, where is that located and what is it. is that the line that separates the back two lines cause if so i did replace that, not sure what ur talking about, please explain

 

There are three rubber flex lines on your truck. One at the back that drops from the frame to the rear axle. And there is one at each front wheel that goes from the frame to the front calipers on each side. If the hose has collapsed on the front lines, it will act as a check valve causing the front calipers to stick.

 

I agree with Swartlkk. These things collapse (usually at the mounting tab where they crimp them on). If you pull one and cut the end off, run a wire down the hose. If it's collapsed I'll bet the crimp area is where you'll find yor problem. The things are pretty cheap and if you've gone this far into the brakes it's chump change. Usually the front hoses are the problem. The proportioning valve (it's called a combination valve) does more than proportions the brake fluid flow from front to rear. Is your brake light on when you don't have the parking brake set? If not then the valve is probably not your problem. They're pretty pricey unless you can get one from a junkyard.

 

thanks guys, i plan on changing those lines saturday. One more thing. the front right side brake lines are the only lines out of the four i did not replace. i took the caliper off and put the end of the line into a water bottle and press the brake pedal. only a tiny bit of fluid can out, should a lot be coming out. Does that mean that line is clogged. The fluid that did happen to go into the bottle had rust pieces floating around. This might be my problem. Ill be changing the lines and the flew hoses this weekend. let me know what you think. thanks