I HAVE A 1989 CHEVY S-10 BLAZER 4.3L APPROXIMATELY 180,000. I HAVE A BRAKE LIGHT ON THE DASH. I REPLACED A BRAKE LINE GOING FROM THE MASTER CYLINDER TO THE REAR BAKE HOSE. I HAVE TRIED TO BLEED THEM BUT CAN'T GET ANYTHING TO WORK. THE FRONT BLEEDS FINE BUT NOTHING OUT OF EITHER REARS. I HAVE TRIED EVERY IDEA EVERYONE HAVE SUGGESTED AND NOTHING IS WORKING. I WAS WONDERING IF IT WAS THE PROPORTIONING VALVE UNDER THE HOOD OR THE ONE ON THE REAR AXLE? I AM OPEN TO ANY SUGGESTIONS THAT CAN BE OFFERED. ALSO THE PEDAL GOES ALMOST ALL THE WAY TO THE FLOOR BEFORE IT STOPS. I HAVE ALSO REPLACED A MASTER CYLINDER,PASS SIDE REAR WHEEL CYLINDER, REAR BRAKES,BRAKE LINE FROM WHEEL CYLINDER TO REAR PROPORTIONING VALVE. PLEASE HELP I AM TRYING TO GET IT FIXED BEFORE WINTER.

Is this truck equipped with rear wheel ABS?




78 Corvette Pace Car For Sale-18k mi orig-Florida

no abs at all.

Make sure that is actually true. the old Blazers didn't really have any marking to indicate there was. The only indication was a flat, verticle module next to the master cylinder. If it has the ABS, then you could have a dump valve pocketing air, otherwise you would be looking at a bad master, proportioning valve or bad rear brake flex hose. I would try capping the line at the master and see if you can get a good pedal.




78 Corvette Pace Car For Sale-18k mi orig-Florida

ok do u mean a flat black box next ot the master cylinder if so then it has rear wheel abs.

Yep, here's what it looks like







78 Corvette Pace Car For Sale-18k mi orig-Florida

Also the other thing is I am kind of confused on is we cant get any fluid out of the what I call the proportioning valve under the hood. But apparently I am getting fluid somehow back to there because I am leaving puddles right where the line meets the rubber line by the rear axle. This is confusing because people tell me that I should try to bleed it more and that still did not work could not get any fluid to the rear wheels. When you push on the pedal it just about goes all the way to the floor. So what steps would you suggest that I take to get fluid back to both rear tires so I do not have to worry about getting into an accident???? Please help I am stuck.

What exactly do you mean by capping the line at the master cylinder? How do you do that?

Capping it off means removing the line from the master cylinder a making something to seal off the hole and see if you can bleed the master alone enough to get a good pedal. That will tell you the master is good and the problem is further down the line.

You might want top try bleeding with a pressure bleeder also.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Guess I'm whacked today but to add to Hammer's list of great suggestions:



A hand held vacuum pump on an open bleeder (use clear line so you know fluid is coming) can work with some feisty but good systems. Don't allow fluid into the pump is the reason for clear line (fish tank stuff etc) will do and it may snap to.

Master cylinders if older don't like pedal to floor sometimes and fail traveling further than they have with crust tearing it's rubber seals inside it even when and if it wasn't a problem to begin with,

T
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Tom Greenleaf - MetroWest, Boston

One basic trick you can use is just start at the Master, find the rear brk line, have some one pump the pedal & crack the line slightly. If fluid comes out, move down the line to the next fitting & crack that one after pumping the pedal. Keep going until you find an area where you don't get fluid when you crack the line....... That's going to be your problem area...........

Well it does have a new master and I have been noticing that when you take off the cap there is suction but i have been seeing that there is a leak at the line before the rubber line where I replaced the line to. that is what so confusing because apparently there is fluid to that point, but when cracking the lines off the proportioning valve off the master cylinder for the rears there was no fluid coming out.

Well - you have to replace that section of line that leaks to the splitter that's on the rear differential. Did you "bench" bleed this master cylinder till no more bubbles showed up?

Was it a new or rebuilt? Have to tried to plug it off to get a firm pedal to rule out defective or air locked up master cyl?

Could be wrong on this but usually the front-most port on master is for the rear brakes. You said one rear wheel cyl is new and I'd make sure bleeders work - take them out till air can blow thru them if needed. The new one should have a new bleeder.

This will come to pass. I do suggest you replace wheel cylinders in pairs also,

T
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Tom Greenleaf - MetroWest, Boston

We did bench bleed it and there were no more bubbles and it was a new master no rebuilt. Both bleeders were working on the wheel cylinders but no fluid coming out of either one of them. I havent tried any of this yet gotta wait. thanks for the help

So far from what I under stand with this problem is there's no fluid pressure at all to rear brakes. You could put the adaptor back on and re-bleed just the rear of master and see if it flows at all now. It might have an issue/fault or be defective even new. In a career I've only seen two defective new ones but it can happen or it's got a huge air pocket as you said you can't get fluid to the proportioning valve even AND had that leak which could have sucked air back in and make it difficult. If you can - get a solid plug proper item to plug the rear system off and you should have a normal feeling brake pedal. If not there's air in master to be re-bled or it's defective is best I can guess.

There's nothing more frustrating than a defective new part and if you returned it get a different brand as the times that happened to me it was a flaw with the whole batch. Unfortunately it puts the burden on you to determine that a part is bad and that's why you are here of course to figure out what's wrong as this should not be this difficult. A pressure bleeder would force fluid thru unless there was a blockage. You could even crack line right at master and see fluid come out. If you let off of the brake pedal if doing this that way with a helper it will suck air back in until all is re-tightened, then pump up and do again and again till air is out. You would need to start all over if master lost fluid and so on.

Are you up on brake bleeding?

(pic shows common bench bleeding. Some can still be done on vehicle but best if done first)

T
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Tom Greenleaf - MetroWest, Boston