Archived Help w/ brakes

[ndurbin]

It all started the other day when I was screwin around and I was power braking slightly. I heard a loud pop and the brake pedal went to the floor. I checked all the lines over and found a worn spot on the front driver side I replaced it and bled the system of air. But after that the pedal is still soft. I dont get anything solid until about the last 1" of travel then it feels alil more solid. But it's still like trying to stop a freight train with a feather. I can't find any other leaks on the lines. Then today I had to run some errands and if I hold the pedal to the floor like at a stop light for awhile the next time I go to use the brake pedal it's harder to push but still goes almost to the floor before I get any real stopping power. So am I wrong thinking its in the master cylinder or booster since I can't find any holes in the lines?



TIA

Nathan

 

[blacksheepdiesel]

ndurbin,



Did you check for leaks at the calipers and especially the wheel cylinders?



Trent

 

[B.G. Smith]

Sounds like the proportioning valve may have switched over from the leak on the line and hasn't switched back. The valve is mounted below the master cyl. and has two lines going in and two or three going out, it also has a wire plugged into it. If your "brake" lifght in the inst. cxluster is working, it would be on. You can check the valve with an ohm meter to determine if it is switched. With the meter set on ohms, unplug the wire and hook one lead to the terminal and one to ground, should not get a reading. If you get a reading, you have to bleed the brake that is working, either the front or the back, slowly depress the pedal while watching the meter, when reading clears, stop and close off bleeder. bg

 

[CrewCabDiesel]

Have you bled the entire brake system ? Before you start pulling things apart try bleeding the rear brakes, You might have a ton of air in the system when the front line blew and might have lowered the brake fluid level to the point of allows it to suck air. the master cylinder reservoir is small and you can empty it quick with a blown line. If the proportioning valve is stuck it might free by releasing the pressure on the rear brakes and bleeding them. When you go to bleed the brakes work from the farthest point from the master cylinder. 1st Right rear, left rear, right front, left front. I would flush the entire brake system with Valvoline synthetic brake fluid avaible at just about anywhere like autozone of kmart. I use on a complete system flush about 2 quarts, and have a third on stand by. The reason I use and recommend the Valvoline synthetic brake fluid is I get a better petal and the ABS on the rear wheels dosen't freak out if I hit a bump while braking.

Hope this helps

Kyle

 

[ndurbin]

I went back this afternoon and re bled the brakes. The back axle and front driver side did fine. But on the front passenger side I keep getting a hissing sound, like theres air still in there. If I keep pumping on it, it while go away but soon as I try to use the brakes it turns to mush all over again.



I also finally noticed the ABS light was on. (it's kinda hidden from the way I have the steering column postioned. ) I got it to go off once when the hissing finally went away. It stayed off til I tired to use the brakes then it came back on and the hissing came back.



So I am I wrong in thinking maybe theres something leaking in the brake caliper? I can't see any fluid escaping just keeps hissing at me. And it's only hissing at the front passenger side.



TIA

Nathan

 

[B.G. Smith]

Since that is the side that had the leak and the light comes back on when you use the brake, sounds like you still have air in the front lines. A good way to tell when the air is out is to get you a piece of hose that will fit tight over the bleeder screw, put the other end in a clear container, clean and large enough to hold a few ounces of fluid, open the bleeder screw, hold the hose so the end is at the bottom of the container under the fluid level(so air can't be returned to the system when brake pedal is released) have someone slowly pump the brakes until no more air is present, close the bleeder, check all wheels but I suspect most of the air is in the front lines. If you push the pedal until it feels hard resistance while bleeding, the proportioning valve will switch over and block the end(front or rear) that you are bleeding. When you get the air all out, bleed whichever brake you have to slowly until the light goes out then stop and tighten bleeder screw. bg

 

[ndurbin]

This is on the oppisite side off the blown line. The blown line was on the driver side. I'm having problems with the front passenger side.



I'll repeat the process in the morning



Thanks

Nathan

 

[ndurbin]

I bled the front passenger side again today until the ABS light went off. tested the brakes and the light came right back on after a half dozen pumps on the brakes.



TIA

Nathan

 

[B.G. Smith]

For the light to come on, there has to be greater pressure on one side of the valve than the other, (front or rear). This can be caused by a leak in front or rear system, the rear brakes need adjusting real bad or a piston bypass leak inside the master cylinder. Are you losing any fluid from the master cyl. ? bg

 

[ndurbin]

I haven't checked the adjustment on the rear brakes for awhile. So I'll go do that. And yes I am losing some fluid from the master cyl.



Thanks

Nathan

 

[ndurbin]

I checked the adjustment on the rear brakes, they were alil loose but not much. ABS light did the same number, went out and then came back on after a half dozen pumps of the brake pedal. The brakes felt pretty solid until the light came on, then they were back to being mushy.



TIA

Nathan

 

[Eric_77]

When replacing lines it is really hard to get the lines bled. I would say you still have air in the lines. I would get a speed bleeder as I bet there is air trapped in a high point in the system. Other way is a trick we do when replacing MC lines with stainless is to apply just a little brake and leave like that over nite. What that does is leave system in a sort of open state where fluid can run down and air can rise to the top. Other thing to try is go through the system and burp everything to the top. Start at the wheel and bend or pull everything so an air bubble will head up towards master cylinder (reason to go this way is that you cannot pump/bled/close repeat fast enough for a large air bubble to go to caliper it gets hung normally in the loop in the flex hose from frame to wheel),leave reservoir open and watch as someone pumps the brakes do you get air bubbles back up trough reservoir? Keep pumping and taping/bending on brake lines until you see no more air coming to the top. Then at that point bleed at the bleeder valve on the caliper. The reason the front right would now have air while front left is fine is that the left side is more of a straight vertical shot and air rises up quicker and easier while right side is more horizontal.

 

[B.G. Smith]

Originally posted by ndurbin

And yes I am losing some fluid from the master cyl.



Thanks

Nathan

If you are losing fluid from the MC when not bleeding, you have a leak somewhere, get truck on driveway where you can see if it is leaking and pump on the brakes(if the light is on, the leak won't appear as it is closed off). May be a rear wheel cyl. and just hasn't leaked enough to show up. Annnnd it could be near that passenger side caliper that you heard that "hissing" sound. Lots of good suggestions from those above. bg