Bleeding brakes nothing will work

[6.2diesel]

So I replaced both front calipers after one was locked up. Now I come to the point to bleed my brakes. Service manual says to hold open a valve but doesn't say how. Any advice will help. Truck is a 1986 c30 2wd. Front brakes.

 

[1low4x4]

Combo proportioning valve

 

[chengny]

I guess - when they say open the valve, they must be referring to the bleeder fitting. It is a little plug with holes drilled in it. The holes get opened to the chamber that contains the brake fluid when you loosen it - and it seals off at the bottom when you tighten it.

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The basic procedure is :

1. Open the bleeders one by one (starting at the brake that is furthest away from the master cylinder). Just crack the bleeder open - maybe a half turn.

2. When you have the bleeder cracked open, have an assistant slowly pumping the brakes. Each time he's pushing the pedal all the way to the floor. Brake fluid will come squirting out of the bleeder.

3. You will be watching at the bleeder for when the stream of brake fluid no longer has any air bubbles coming out with it.

4. Don't forget to keep the master cylinder full of brake fluid while you bleed the lines - you will use a lot of fluid.

5. Anytime that your assistant stops pumping the brake pedal, one of two things has to be done:

a. You must close the fitting snug. Or
b. Your assistant must push the pedal to the floor and keep it there.

If one of these things not done - when the assistant lets the brake pedal come back up, air will get sucked back into the bleeder and you will have to start all over again.


If you can find a length of rubber hose and a glass jar, that makes it easier to see when the bubbles (air) is completely purged from the line:

Open the bleeder and snap the rubber hose over the tip. Put the other end into the glass jar and have the helper start pumping. The mixture of air and fluid will spew into the jar. At first it will be mostly air, then about half and half and when the line is bled properly only brake fluid will come out of the hose (no bubbles = a bled brake line).

At that point yell to the assistant to "Push the brake pedal all the way to the floor and HOLD IT THERE!"

While he holds the pedal down, you take a (6 point) socket and firmly tighten the bleeder fitting. I say firmly, but do not go all Neanderthal on the fitting - they are like little valves and can twisted off if over tightened.


That's one brake bled, go around and do the others the same way.


I wrote this wicked fast and it probably contains many mistakes and/or omissions.

 

[chengny]

If they are talking about the CPV, just disregard that nonsense. You only have to deal with that if you are unable to get flow to either both the fronts or both the backs. That isn't your situation.

 

[1low4x4]

sorry, I guess the headline was kind of misleading, bleeding brakes nothing will work. Led me to believe is combo valve was stuck

 

[6.2diesel]

Well i pulled the brake line. There is no fluid making it to the caliper on the side it was locked up on. Is this why we couldn't get anything to come out? Is the line shot?

 

[robert8096]

Check the rubber brake hose going to that caliper. They are known to rot from the inside and restrict fluid flow. Change both sides and the rear one if you find it's bad.

You can check by removing the capture nut that holds the rubber line to the frame and gently pull the metal line thru the frame. Gently separate the metal line from rubber line and see if you get fluid flow.

 

[firebane]

I had to pull a bleeder screw out and drill it because so much dirt had built up and was letting it bleed properly.

 

[1low4x4]

Both good points^^^

I also had to pull a bleeder screw screw poke a pick in there.

 

[Scottycutlass]

I have had this issue before on my Dads truck. I have a power bleeder and that didn't help either. In the end I found the brake line to that wheel was plugged and had to be replaced. The reason they plus is because when the breaks get changed people push the pistons back into the cylinders with out wiping them off first and then that contamination gets into the break line.

Newer vehicles are even worse for this issue since the caliper pistons are made out of ceramic or plastic.

 

[6.2diesel]

Thanks guys. It was the brake line. Collapsed and that's why the caliper locked up in the first place. Oh well, 30 year old brakes they needed it anyways.