Brake Problem

[junkyardpartseeker]

Today, first, my brake light came on. Now, when I stop, my pedal feels spongy and sounds like squeezing air when I press the pedal if you know the sound I am describing.

Thinking my brakes might be out of adjustment, I accelerated in reverse and hit the brakes. Both front brakes locked up, but the rears did not. I did this many times. Still the same.

Other than this, I have done nothing else or checked anything else.

Any suggestions on what to check would help. I am off tomorrow and am planning to look at it then.

Thanks
Tommy

[bigblock73]

Have you checked your PB booster resevoir yet? When you open it and if it (the small compartment, for the rear brakes) is empty, it means either a wheel cylinder is leaking or you have a hole in your rear line somewhere. Look at the inside of your rear wheels...see if you see brake fluid on the rim or tire.

[junkyardpartseeker]

reservoir is full of fluid, and I looked under the vehicle at the rear wheels. No visible signs of fluid leakage. I have not pulled my wheels yet.

Tommy

[rolson1039]

i would check the rears for being out of adjustment. if brakes dont lock up in the back when fronts do therye prolly out some. check for a small leak all the way from the master down to the back wheels then pull the drums off and check the wheel cylinders adjust them after you stick the brake drums back on

[N2TRUX]

Originally posted by junkyardpartseeker
Today, first, my brake light came on. Now, when I stop, my pedal feels spongy and sounds like squeezing air when I press the pedal if you know the sound I am describing.Thanks
Tommy

It sounds like you have a blown master cylinder too me.

[BigRed]

Tommy, I would suggest first bleeding the rears and then the fronts and see what that does for you. If that doesn't work, I would try adjusting the rears (like others said). Good luck!

[junkyardpartseeker]

Here is an update of what I have done:

I found the right rear metal brake line broken, replaced it, and the left rear wheel cylinder leaking, replaced it.

I also went and got another master cylinder.

I have fluid bleeding from the bleeder valves from the rear cylinders, the pedal still feels spongy and my brake light is on. I have also tried several times to go in reverse and hit the brakes to adjust them. No luck so far.

Any other help would be appreciated, I am going nuts racking my brain on this one.

Thanks
Tommy

[Free88]

HI. When bleeding your brake lines always start with the one the farthest from the master cylinder, and then the next farthest, and so on until all four are done. Keep an eye on the master cylinder and make sure that it is always full, and you replace the cover at each refill. A brake bleeding bottle actually works the best. You can buy one but you can make one cheaper. Cut a hole in the top of a platic bottle cap, insert a hose that will fit over your bleeder screws, half fill the bottle with clean brake fluid and then put the cap back on with the hose all the way to the bottom of the bottle. Seal off any opening with some plumbers putty or hot glue, or tape, just make sure it is sealed. I always fill the line before putting it on the bleeder. Push the open end of the hose over the bleeder screw and have some one pump up the pedal and hold it as you slowly release the bleeder screw. The air will go into the bottle, and this way you will suck any air back in when you tighten the bleeder screw. have the other person pump the pedal again and continue at each wheel until no more air comes out, then go the next bleeder and repeat. NO mess and works very well. Make sure to keep checking the m/c full. Works for me.

[Grim Reaper]

Originally posted by Free88
HI. When bleeding your brake lines always start with the one the farthest from the master cylinder, and then the next farthest, and so on until all four are done. Keep an eye on the master cylinder and make sure that it is always full, and you replace the cover at each refill. A brake bleeding bottle actually works the best. You can buy one but you can make one cheaper. Cut a hole in the top of a platic bottle cap, insert a hose that will fit over your bleeder screws, half fill the bottle with clean brake fluid and then put the cap back on with the hose all the way to the bottom of the bottle. Seal off any opening with some plumbers putty or hot glue, or tape, just make sure it is sealed. I always fill the line before putting it on the bleeder. Push the open end of the hose over the bleeder screw and have some one pump up the pedal and hold it as you slowly release the bleeder screw. The air will go into the bottle, and this way you will suck any air back in when you tighten the bleeder screw. have the other person pump the pedal again and continue at each wheel until no more air comes out, then go the next bleeder and repeat. NO mess and works very well. Make sure to keep checking the m/c full. Works for me.

That farthest from stuff is BS. It's better to bleed rears first (side doesn't matter as it T's on the diff) then bleed drivers front.

The reason to do drivers front is the hard line off the Combination valve is on top and it's going to prevent air from getting into the passenger side line if you bleed it first.
Othewise the rest of this info is great.

You might have to pull the pin on the hold off valve on the Combination valve. Looking at the CV on the front cross member the side pointed to the driverside has a rubber cover on it. If you pull that off it will expose a mushroom shaped plug with a pin in the middle. If you push on the mushroom part it will expose the pin and you can grab it with some locking plyers and pull it out about 1/8 inch. BECAREFUL not to smash the pin in such a way that it can't freely return to it's rest position. There is a tool for this but pretty hard to find.

Once that pin is pulled it should gravity bleed very easy and you may beable to do the rest of the bleeding with aout assistance.

[Free88]

Gee I guess the manuals and auto instructors have been given false info all these years. Backs are done first as My note states. Not trying to cause a scene but if you read the Haynes manual or any other truck manual they tell you to start at the right rear wheel, then the left rear wheel, the right front, and finally the left front. And oh ya always bench bleed the master cylinder before installing.

[Grim Reaper]

Originally posted by Free88
Gee I guess the manuals and auto instructors have been given false info all these years. Backs are done first as My note states. Not trying to cause a scene but if you read the Haynes manual or any other truck manual they tell you to start at the right rear wheel, then the left rear wheel, the right front, and finally the left front. And oh ya always bench bleed the master cylinder before installing.

\


Hay I been doing it farthest first for a long time. Not sure where that came from but look at the logic. Why would you bleed a line that might get air in it a second time if done first?

I think that wives tale dates back to single circuit drum brake days. On a single system it would make sense to get the lines with the most potential air cleared first.

Now I will agree ALWAYS do the rear first. The reason being is if you look at how the master and the CV are designed the rear piston in the master drives the front piston with fluid pressure and not a mechanical connection (If pressure is lost it will bottom and drive it mechanicly). You have to get that air out of the rear first to make bleeding the fronts easier.

On the CV you also ned rear pressure first because the front circuit has a hold off vlalve to alow the rears to take up any gap that he disks don't tend to get as much of. The fronts don't start activating till there is about 60-90 psi.

http://coloradok5.com/atrondiskbrakes/74disc13.jpg

Look at the CV. Tis is mounted on the front crossmember and if you head was under the oil pan this is the way it would be mounted. On the left is the front outlets. WHere it's beveled at 45 deg on the top left is the front driverside connection. The front passenger side is straight into the bottom.

Now air rises in fluid...doesn't it make sense to bleed the line that is going to get the most air out first?

Here is the whole link for the write up I did.
http://coloradok5.com/atrondiskbrakes.shtml

[Free88]

Thanks for the info Grim Reaper but I will stay with the way the manual states and the way I have been doing it for years. I am not a master mechanic and if I have upset you in any way my apologies.

[84Stepside]

Had that problem,brake light came on, checked the brakes, front discs fine , rear brakes got the treatment , turned rotors, new pads, breaklight still on. Turns out my problem was my proportioning valve had quit working. Replaced, rebled, no brake light.
T