Brake problem , at witts end.

[Fordbinder]

Okay guys I have a 94 cc dually 7.3 i.d.I. had breaks but not very good so I investigated. Former owner had put on new shoes,pads,drums and rotors- great right. Well I noticed wetness all over rear backing plate so I tore into it the guy had a wheel cylinder puking so he replaced it but did not clean up the mess and it was bad almost like an axle seal leak but not. So I buy new shoes and put them on, go to check master cylinder well just because. as soon as I twist cap I hear this giant sucking sound and wala-
no brake pedal i.e. no brakes to speak of. So I take it to Car x and have them power bleed the brakes, go out to truck to leave -no pedal so they bring it back in and rebleed it.. still no pedal they say try it maybe it will come back. Also say they think master cylinder bad. So I take it home put on new master cylinder bench bleed then do wheels no better so I go back to Car x they bleed again little pedal but it fades they say it is as good as they can get it. So I try to bleed it myself find two plugged bleeders so go back to Car x they re power bleed -no pedal. Was advised maybe new master was bad so I get another , bench bleed it then bleed allfour wheels. Pedal until I drive it then it fades again. I am thinking bad booster but afraid to put out anymore money. Any similar experience,any advice??????????????? Supposed to leave for San,Antonio on the 20th , but not with brakes like this.

 

[steelheadguy]

After you cleaned the wet rear brakes from the leaking cylinder, did you notice any more leaking?
If he didnt clean up the leaking brake fluid, I wouldnt trust his work. Are you sure he replaced the wheel cylinder?

Id say it was the masyer cylinder but you said you already tried a new one. Maybe look for vaccuum leaks or yea the booster.

 

[rotarydragon]

Have you tried pulling the hose off the booster? Should have a stiff pedal with it gone. Is it draining the fluid?


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[icanfixall]

A sinking brake peddle usually means a bad master or the dreaded rear shoes are really far out of adjustment. Our self adjustable rear brakes DO NOT WORK. Also sounds like this shop had no idea what they were doing other than getting bucks from you. Driving a truck or car "hoping" the brakes will come back is silly.
Heres what you can do. Buy a brake adjusting spoon. Manually adjust up the rear brakes. If the drums were ok and did not have a wear lip then remove the drums and adjust up the brakes. If you do not want to remove the wheels and drums just use the brake spoon thru the small opening. the brakes only expand one direction. I don't remember if the spoon is moved up or down to adjust. I think the spoon touches the bottom of the adjuster star wheel and you press down to turn the wheel upwards. A really easy way to determine if the rear shoes are too far out of adjustment is apply the parking brake. See how far down the brake peddle goes after that. Drive slowly when doing thes.

 

[pickupman]

I did my rear brakes a couple months back and after finishing the brake pedal was really mushy. It was my first time doing them, and I though I had adjusted the brakes correctly, but it turned out that I hadn't.

What I had to end up doing was with both the rear wheels off the ground, adjust the stars until the wheels couldn't be turned any more. Then I backed off on the adjusters until the wheels could spin freely with just a slight among of drag. Doing that solved all the braking issues.

 

[79jasper]

Sounds like a combo of rears out of adjustment and maybe front rubber lines expanding.
I would say the rear wheel seals are leaking too. It's pretty common.

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[Fordbinder]

Thanks for all the responses guys, I have a mechanic going to check it out for me, he seems convinced that the proportioning valve is the problem. Will advise after I get truck back. Again thanks for the responses!

 

[typ4]

Hes likely wrong, the system is sealed, a bad prop valve just messes up the brake bias. Your booster may be bad and causing the master to have air intrusion.
If it was a chevy I would agree with the prop valve.

 

[79jasper]

Hes likely wrong, the system is sealed, a bad prop valve just messes up the brake bias. Your booster may be bad and causing the master to have air intrusion.
If it was a chevy I would agree with the prop valve.

Yeah, I agree. Considering it doesn't even have a prop valve. Lol


I once seen someone say the prop valve is under the driver on the frame. And the RABS is behind the glovebox. Lol
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[KZF250]

When they bleed the system are they bleeding the Rabs after the two rears? Rabs could have air in it, dirty from old brake fluid or just bad. I have been working on getting a better peddle and it improved after including the Rabs in the bleeding process but still not what I would like. I pulled the unit this morning and the ports were nasty so I'm going to open it up and check it out tomorrow.

 

[yARIC008]

My vote is rears are out of adjustment. Unlike disk brakes which are basically againt the rotors at all times, the drum brakes have to travel to get to the drum. Even a micro inch out if adjustment will feel huge at the pedal.

 

[icanfixall]

When the rears are way out of adjustment the fronts do ALL the braking. that overheats them till the rotors crack or warp.. Not fun. Also when you finally come to a stop the peddle very slowly sinks and the truck creeps forwards. Again.. thats not fun. Mechanically what happens is the fronts do the stopping and the sinking peddle is the master trying to fill the out of adjustment rear wheel cylinders. It can do it but it is not done when it should be done as when the brakes are applied. Manually adjust up the rears. Also if the parking brake peddle sets at the floor or very near the floor you have way out of adjustment rear brakes.

 

[The Bus]

A friend of mine experienced similar issue with his Ford Dually. He replaced parts, power bled, and bled, bled, bled his system. Did I mention, he bled his system?

So he decided to bleed them one more time manually about a week or so later. This go around he heard a very slight hiss from the bleeder screws in the rear when he released them. So he went around each of the bleeder screws, pumped the break peddle, held it, released each of the bleeders until he heard nothing.

No more brake issues.

I think what might of happened was air intrusion at the bleeder screw or other fitting - it does not take a lot of air to cause problems from what I have been told. I also suspect there was no grease on the threads to block air intrusion either.

A hydraulics mechanic warned me about suspended air/contaminants trapped into the fluid when I inquired about the issues my friend had with his dually. He said there is a lot of causes and is not all that uncommon in braking systems given the make up.

He told me that it takes time (patience) and fluid to get it out of your system.

A way to check is to put a piece of clear tubing (make sure it is tight) on the suspect cylinder bleeder and loop it so that an air can be trapped while allowing fluid to escape (think gravity bleed). Make sure air cannot penetrate the bleeder screw threads - a little grease on the threads. Open the master cylinder cap and then open up the bleeder screw to allow the fluid to flow slowly into a clean (pref clear) container - you'll need to check this later. Make sure to keep the reservoir topped off and monitor the tube for signs of air and particles (rubber, metal, dirt, and water). You'll have to gauge your time as to what is present or not present for about 5 minutes or so - my experience. Your not really bleeding, but looking for suspended air and contaminants.

By the way, a problem for some of these Fords is the abs system. If you have rear abs, you might have that dreaded RABS valve that mounts under the master cylinder. Those things are a pain in the XSS, expensive to replace, and difficult to find.

Once you have allowed some fluid to flow and inspected the tube, tighten the bleeder. Inspect the container for contaminants. If you see anything other than clean brake fluid, you'll have an idea of a potential problem and can trace backwards to the source - like the rubber line from the frame to the rear brakes.

I found tiny rubber particles when I did this on a front caliper on my bus. A brake hose that looked to be in good shape, showed no signs of swelling was deteriorating from the inside. I was experiencing fade and a very, very slight pull at times.

I hope this helps.

By the way, the sucking sound was made by not taking off the master cylinder cap when power bleeding. A vacuum was created in the when drawing the fluid out of a closed system.

Before I forget, they make a tool for setting your brake shoes: http://https://www.amazon.com/GearWrench-3377-Brake-Resetting-Gauge

A friend of mine swears by this tool as a real time and money saver. Discovered his new drums weren't true the first time he used the tool.