no rear brakes and hard pedal?

[70396CST10]

Hello all:

I have front disk brake with power brakes..

I was doing maintenance on my new project Saturday and went to check the fluid in the MasterCylinder and the fluid was very low in the front and there was no fluid in the rear.. I added fluid and tried to bleed the rear but no fluid comes out at the back... Front bleeds fine..

Brake pedal is hard and the brakes do not work very well.. The front wheels will not lock up..

How can the brakes work if there is not fluid in the rear? Wouldn't the pedal go to the floor? Is the prop. valve stuck or something?

Thanks in advance..

James..

oh yeah,

I did a search..

Thanks again..

[special-K]

Blockage?Did you pull your drums?Are the cylinders pushing?Could be frozen and dry.

[Big Block]

Your proportioning valve could be bad or possibly clogged. I have had this problem before. I replaced it with a used one I had and it work fine.

[StormRider]

Like Special-K said, I would pull the rear drum off and have someone step on the brakes to see if the wheel cylinder is pushing. Then work your way up from there....proportional valve....master cylinder. Your fluid being that low means that either your brakes are shot or have very little life left or that there was or is a leak somewhere. I've had to take lines out one end at a time and see if fluid is flowing or not. Shouldn't be too hard to locate or fix...just need an extra hand (or leg)

[70396CST10]

Thanks for the help guys..

I had a friend try and help me bleed the brakes and there was no fluid at the drums so I assume the wheel cylinder would not work without fluid..

We even tried bleeding the line right off of the master cylinder for the rear brakes and there was no fluid there either but the bowl was full.. Maybe the master cylinder has gone bad? How could the front have fluid at the front bowl working and not at the back.. I wonder if the bowl hole is clogged or something.. I am just trying to save myself from throwing parts at this thing to fix it..

I'm thinking master cylinder, prop. valve, or booster also maybe..

I drove the truck this morning to work and the pedal is very hard with little brakes.. And if you pump the brakes then they work even less..

I will try a master cylinder and prop. valve and see what happens.. I believe I have a couple laying around off a nova that had disk brakes..

I also did not check my front pads after bleeding the front brakes so maybe they are about gone.. I figured I would still have decent brakes with the fronts working but the brakes are scary horrible..

I am new to these trucks so all the help is really appreciated..

Thanks guys and I will keep everyone updated..

James..

[kbs71]

If the back bowl was completely empty of fluid, try bench bleeding the master cylinder. I wound up taking my prop valve apart cleaning it up with brake cleaner and reinstalling it. Just remember how you took it apart. Then try bleeding your back brakes. It may take several bowls full of fluid to fill those lines and cylinders back up. keep bleeding tilll you see new fluid coming out and no bibbles. next do the front one the same way. It's best to do the right rear first then the left rear, right front and finally the left front.
But sounds like the MC needs to be bench bled first.

[70396CST10]

Thanks for the response..

I have never actually ever had to bench bleed a MC before..

What are the steps I need to take?

Thanks..

James..

[69TowRig]

You will need plugs for the ports on the MC. Put the MC level in a vice or something to hold it, then pour fresh fluid in the resevoir. Keep slowly pushing the piston on the MC in with a screwdriver (about 1" and no farther) and letting out until no more bubble float up in the resevoir (keeping the resevoir topped off of course).

Then when you to to hook the lines back up try to do it as quick as possible so as not to get air back in the MC, then re-bleed everything and go from there.

If you find that your proportioning valve is acting up, do a search on here there are instructions for re-adjusting that as well (but I can't remember where).

[70396CST10]

Thanks for the help..

I hope to try some things this weekend and I will post up the results..

thanks for the help..

James..

[Huck]

James--the fluid went somewhere outside of the system so you have to find that leak or you are wasting your time. I would do the following - get a new or rebuilt master cylinder and rear wheel cylinders===this is a cheap buy. Most master cylinders will come with instructions on how to bench bleed with plugs etc. Replace all three items. Then try to bleed--if you get no fluid out the back---your proportioning valve is stuck. This little bugger has a piston that moves forward and backward depending on fluid between it and the brakes--. It could be stuck anwhere in it's path driving you nuts. You could have a rusted brake line anywhere--common on these trucks--that leak or blocks fluid so be sure to check the lines. The rubber hoses could also be shot by this time too---. Go for the cheap fix's then work backwards to the proportioning valve as this is the most expensive part of the system. Good luck--Huck

[70396CST10]

Thanks Huck,

I will definitely do it in that order.. I'm going to start with the MC and go from there.. I'm hoping to find some time during the week in the evening or Saturday at the latest to figure out this problem..

Thanks for all the help guys and I will keep everyone posted on the progress.

After this I have to get started back on trying to get my fuel gauge to work.. New float did not fix it.. lol...

Thanks again for all the help..

James..

[70396CST10]

**UPDATE**

Well Huck, you were right.. I worked on the truck some yesterday.. I checked the fluid again and sure enough, the rear bowl was empty again.. So I replaced the MC with one I had on the shelf.. I was getting fluid through the rear line so I tried pumping the brakes to see what happens.. Sure enough, another hard pedal.. I was stumped.. So I check the fluid again and it is empty.. I look under the truck and bingo, fluid on the shop floor at the back of the truck..

Problem.::::

Rear brake line that connects to the rubber hose at the rear was broke right at the fitting...

So I guess I will be replacing that line... I took it off yesterday and man is that line long..

Only thing I hate is that the line that broke is probably between 95-100 inches long.. Can you get lines like that at the parts store?????

Question::???? How could the brake even work with the fluid leaking out like that? I had a hard pedal and little brakes but I figured with a broke line there would be no pedal at all????? Confusing..

Thanks for the help guys and I will post up how the brakes work after replacing the line and bleeding the brakes again..

[Huck]

Hydraulics do not work when your fluid leaks out--. That is the biggest problem with that stuff. With the rear not working, you are only getting marginal help from the front---but the proportioning valve is working against you that's why the pedal is hard. To properly bleed your brakes (according to the GM shop manuals) you need to hold in the pin which is at the front of the prop valve (sometimes covered with a rubber boot). You can either fab a tool or use a big C clamp--pipe vice--or other creative thing. With this pin held depressed, then bleed your entire system starting at the LR then RR, then LF then Rf. You can bleed with a pressure system (best) or via "pump the pedal and have partner work the wheel cylinders/caliper bleeders" or with a vacumn system.
Now that said, I have been dealing with a similar problem for some time---so I know your frustration. Once done and working, it usually will be fine for years ~~~. Good luck--Huck

[70396CST10]

Well, I got the new brakes line put on Saturday and thought I was headed for success... I filled bowls up with DOT 3 and had my wife help me by pumping the pedal for me.. At first I had fluid at the rear with no problems and I bled all four corners.. But when I jumped in the truck and tried the brakes they were no different.. Still a hard pedal and hardly any brakes... So I run to town in the truck for the wife to get some sugar and while driving it the pedal starts to free up like or starts going all the way to the floor and I was loosing all brakes.. Well, now I have no brakes and now the pedal is soft and goes all the way to the floor.. Looked for more leaks but found none.. I assume I still have air in the line? I could not get anymore fluid to the back.. I guess I will try bench bleeding the MC to see if that will help??????? But this brake situation is hard to figure out and I don't really have the equipment to do a proper run down on it like a shop would..

but the update is that I have no brakes at all now.. Can't even pump them up so I figure I must have a ton of air in the line???

thanks..

James..

[larry may]

Try bleeding L/F first then ,Then R/F , Then L/R Then R/R...bleed each one individually untill you get a good flow. Keeping the MC full while doing this...my .02%

[70396CST10]

Thanks Larry:

I will try that but it seems like I'm having trouble getting fluid to the rear.. But I will try what you say.. I was doing the opposite.. I started with the rear first... lol..

Thanks again..

James..

[fastwillie 696969]

here what to do youre the only one to pump the brakes
get a clear glass bottle (no wrapper) add new brakes fluid about 1/3 filled
get some rubber hose that fits over the bleeder valve about 18 inch long
make sure the mc is full then start at the futher away from mc r/r first like you did before what i do is mark the fluid on the bottle for starting point and pump the brakes until all the air bubbles stop coming thur and the fluid raises in the bottle do all around and top off mc /did you change the proportioning valve it might be clogged up with crud and some off them have a clip in front that has to be set when bleeding
good luck

[70396CST10]

I have not changed the Proprotioning Valve.. Here is the latest update.. I have tried using a pump that pulls vacuum through the line at the rear to get fluid back there with no luck.. Just pulls air.. So I did the same thing at the MC and plenty of fluid.. So then I did the same thing at the pro. valve and plenty of fluid there also... But no fluid at the back????

And absolutely no brakes at all now.. Plenty of fluid at the front but no brakes at al...

I have now tried opening the rear bleeders and letting the truck sit a couple of days and seeing if the fluid will go back.. Someone told me to try that because it worked for them..

I just don't have enough knowledge or understanding to figure our why there is not fluid at the back line???????????????????

That is the question???? Is the air that bad and keeping the system from allowing fluid to the rear..

I would hate to have to turn this deal over to a mechanic to fix.. I should be able to do this..

Thanks for all the help and just wanted to update everyone..

James..

[68speedalert]

Two questions.....

When was the last time you had a good pedal and was satisfied with the stopping distance?

&

How long has the project been sitting?

[70396CST10]

The brakes have never worked good since I purchase the vehicle on 2-7-07..

The pedal was hard but would stop the truck but barely.. I knew it wasn't right..

And the previous owner purchased the truck on 5-20-06 and was driving it everyday.. But he was fine with the brakes..

Not sure before that..

The pedal use to be hard and the front brakes were working barely but you could not lock them up..

I assuming the small bowl/back bowl is the bowl for the rear brakes correct? Front bigger bowl is for the disk brakes I assume? That is correct, Correct?

Thanks..

James..

[68speedalert]

Originally Posted by 70396CST10

I assuming the small bowl/back bowl is the bowl for the rear brakes correct? Front bigger bowl is for the disk brakes I assume? That is correct, Correct?

That is correct.

The hard pedal may be because the booster isn't working.

With engine off, pump the pedal 5-6 times. Hold it there and start the engine. If the booster is working, the pedal should drop an inch or two.

[70396CST10]

Yes Sir...

Power Assisted brakes with disk up front and drums in the rear..

Thanks..

James..

[68speedalert]

I edited my last post. I read back to your post and saw it was power.....sorry bout that.

[70396CST10]

OK so I worked on the brake problem some more last night..

I worked on figuring out why I have no fluid at the rear wheel cylinders..

I started by taking the rear hard line loose from the rubber line and fluid poured our from the line.. Almost emptied my bowl.. So no blockages from the MC to the rubber line.. I then take the two hard lines loose and inspect the rubber line on the other side.. And no fluid present..

So I take the line loose and blow through it and can't pass air through the line..

So I take the line off my camaro and now I have fluid to the back

But, still no brakes.. Did a complete bleed on the system again and still no brakes..

I have no clue what to do????

I do have fluid to the back brakes now.. But no brakes..

Aggravating truck..!!!!

[68speedalert]

do you mean no hard pedal or hard pedal but it won't stop?