Another Brake Issue Thread

[bvenvert]

Well, I have been all over the forum reading about brake problems and the corresponding repairs and I feel like I might have too much information, if there is such a thing.

Anyway, I have a 91 Ranger 4x4 and I now have a brake issue ,which results in the brake pedal going all the way to floor with little or no braking power. I have tried to bleed the brakes which goes smoothly on the rears and after about three or four tries, I can get the air out of the lines. Then I moved to the front, right side and have spent literally ten to fifteen minutes trying to get the air out of the lines, with no luck. It seems that every time I pump up the brakes and release the pressure through the bleeder valve at the caliper, I have bubbles appear inside the glass jar. I had a friend of mine over to monitor the brake fluid in the reservoir and he says he can see bubble coming up in the reservoir while I am releasing the bleeder valve at the right front caliper. Would this indicate that I have a bad master cylinder? I was under the impression that you should never see air bubbles in the reservior, especially when you release the pressure at the bleeder valve. I replaced the booster and the master brake cylinder three years ago and the truck doesn't get driven that much, but I wouldn't think it would need to be done again already.

I guess my second question is could the ABS or HCU (Hydralic Control Unit) be causing the problem? I am not sure the truck even has an HCU, but I have read on the forum that once you get air in the HCU, you need a special tool in order to properly bleed the air out of the system. Along with this if I had air in the HCU would the vehicle be throwing up an ABS light on the dash? I do not have any lights at this time.

Thanks in advance for all your help.

 

[bvenvert]

Anyone with any ideas?

I think at this point I will just pull the master brake cylinder since I can get it replaced under warranty and see if it fixes my problem.

 

[Maniak]

You only have Rear ABS, and from what I've read from a few places you don't need the special too on RABS systems. You just push the pedal all the way down a few times with the engine off to re-center it.

I've never seen a brake system do what your describing, but I'd be thinking the same thing you are.. you shouldn't be seeing air in the master cylinder..

~Mark

 

[Four0Sport]

how are you bleeding the brakes? the most effective way to bleed brakes is not to 'pump' them, but rather have someone in the truck apply steady pressure to the brake pedal, and have them floor the pedal when you open the bleeder. also, on an ABS equipped vehicle you should have the key turned to the 'on' position.

pumping the pedal actually puts air into the system if you let the pedal come back up with the bleeder open. hope this helps. keep us updated.

 

[Maniak]

Thatis true.. pumping should be done with the bleed screw closed just to build up pressure.. then they hold the pedal down while you open the screw.. when the pedal gets at/near the floor you close the bleed screw and do that again until you stop getting air out of the line..

BUT..

I read the issue being that with the bleed screws closed that stepping on the brake made air bubbles show up in the resevior (sp?) which isn't normal.

~Mark

 

[Four0Sport]

if bubbles appear when the bleeder is closed that would lean more towards pressure bleeding off somewhere in the booster/cylinder, id think.

 

[bvenvert]

Thanks for your assistance. I have been through the brake bleeding procedure a number of times and everything on the rear brakes seems to work according to plan. I pump up the system with the brake bleeder closed to build pressure, then open the bleeder at the wheel with a hose attached that flows to a small jar of brake fluid, making sure to keep the hose under the top of the fluid level in the jar. This is done to ensure that the bleeder valve doesn't pull air back up into the system.

Okay, all that being said, When I move to the front brake on the right hand side I cannt get the system to keep from pushing air into the jar. I go through the process listed above 15-20 times and still get air in the jar when I open the bleeder valve. In addition, we have seen air bubbling back into the master cylinder durig the process, which doesn't seem possible unless something is wrong with the master cylinder.

I guess I am trying to diagnose whether there is something wrong with the system that is going to require a visit to a mechanic or whether or not I can repair on my own. If it turns out to be a master cylinder, I have replaced it on this vehicle before about 3 years ago, so that's not a problem, I just want to make sure I am going down the right path.

 

[Maniak]

It is possible to get air around the bleed screw which will make it look like your still getting air from the brake system.. just put a glob of bearing grease around the bleed screw to keep that from happening..

BUT.. bubbling in the Master cylinder is a different story.

~Mark

 

[bvenvert]

Good point on pulling air in around the bleeder valve, but I think in my case I am going to pull the master cylinder once we get this burst of warm weather over the weekend and have it replaced under warranty from Autozone. Once I install it and bleed the brakes, I'll know if I still have more work to do.

 

[Bigkondor]

This is about my girlfriends 91 Explorer 4x4. The ABS light and red brake light were on, also when I drove it after the lights came on it had no front brakes, only the rears would lock up. I replaced the master cylinder, everything bled fine, but the lights were still on.
After driving it it was fine, and then after a few hours, the same problem only rear brakes, no front. I then looked on here and saw the comment on recentering the valve, by turning the key to on and pressing down. So if you do that everytime before you drive it, its fine, if you dont and just start it and drive off, no front brakes until you do this. Where is this valve, is it in the ABS unit which can just be bypassed as I had read here, or is there a proportioning valve somewhere that needs replaced...Also the ABS light or the red brake light have not been coming on, even when there are no front brakes...

 

[SPMahoney]

ok sounds great...please be kind, but i dont know were this "bleeder" screw is, let alone what to do when i find it...sounds like there's a jar of brake fluid involved, i remember my step-father running a hose ...sucks he's passed; i could really use the Ole Man...

would the Hanes book detail this process? its tough to pic this from Posts, and i dont want to hog the space....

 

[Mettler]

So I wonder, did you ever figure out what was wrong? Im thinking there might be a loose line on the master cylinder.

 

[SPMahoney]

took the 98sport to the brake shop; tech immediately diagnosed that there wasnt enough vacumn being created by the engine...the pedal has initial pressure, but loses that pressure after the first touch...we can cross reference the engine problems i am already aware of, but i didnt realize it would impact the brake system

 

[SPMahoney]

:thumbdwn:took the 98sport to the brake shop; tech immediately diagnosed that there wasnt enough vacumn being created by the engine...the pedal has initial pressure, but loses that pressure after the first touch...we can cross reference the engine problems i am already aware of, but i didnt realize it would impact the brake system

 

[shaggymane]

nice of you to come back and post the outcome. Questions come to mind though. Wasn't it idleing very low or showing a vacumn leak to not have enough vacumn to pull the brakes on properly? Guess it could simply be a wornout vac booster. Or what engine problems were you already aware of?

 

[Four0Sport]

hmm.. im having similar problems with my 93. no leaks, bled the system twice, still dont have very good pedal. I do know that my trans modulator needs replaced, there is trans fluid in my vaccum line going to the trans and going to the FPR. The line going to the booster was clean but I'm wondering if the trans modulator being bad is affecting the motor creating vaccum or affecting the booster? Any ideas?

 

[Tony H]

Good point on pulling air in around the bleeder valve, but I think in my case I am going to pull the master cylinder once we get this burst of warm weather over the weekend and have it replaced under warranty from Autozone. Once I install it and bleed the brakes, I'll know if I still have more work to do.

How did the New Master work for you?
Also When Bleeding. Don't use the 'Pump the pedal, hold it then have a friend crack the Bleeder' method.
instead, take a small jar, put a small amount of brake fluid in the jar run a hose from the Bleeder into the jar and make sure the hose is below the Brake fluid. The hose has to fit tight on the Bleeder. Now pump the Brake pedal about 7 times and then tighten the Bleeder. The hose going down into the brake fluid in the jar acts as a Check valve. you can bleed brakes without any help this way. Also don't loosen the heck out of teh Bleeder one full turn is plenty.