Brake problems

[Deezelcaddy]

My 92 f-350 is still experiencing brake problems. The brake pedal won't "hold". If I put continuous pressure on it it will get pretty close to the floor. I bled the brakes and got nothing but fluid at all 4 corners and the abs valve? Under the drivers seat. I don't want to just throw parts at it buy from my reading it seems that the booster androsterone can fail causing a similar situation. I still have to adjust my rears by hand but when I changed brakes last summer I put all new hardware on so I would hope my auto adjusters are working. I am a bit stumped on this one. Thanx in advance for any advice.

 

[79jasper]

I betcha those auto adjusted ain't doing anything.
Fords are notorious for this.
Adjust them real good, and I bet your pedal comes back.

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[icanfixall]

No mattter how much we hope the self adjusters work. They rarely do on the rears. The simple easy way to know if the rears are out of adjustemt is the sinking brake peddle after a stop or see where the parking brake sets when it holding the truck. If the parking brake is near the floor or more than half way down then you need to manually adjust the rears. What is happening is the front disc brakes are doing most if not all the braking. Thats very ******* them to stop a load too. I found this out many years ago at a very good Midas Brake and Muffler shop locally. I kept cracking front rotors from overheating them. The brake guy was very good explaining this. He told me the shoes needs to be about 25 thousands from the drums to be correct. As they wear and the gap gets wider the master cylinder tries to fill the wheel cylinders. As that happens you feel the sinking peddle as it fills the out of adjustment rear brakes. The dreaded sinking brake peddle is the result. Of course when you stop all feels normal but its not. Your fronts are doing everything for you. Fronts normally do most of the stopping but they are not made to do all of it.

 

[Black dawg]

Out of adjustment brakes will cause LOW pedal, but will not cause SINKING pedal. For the pedal to sink, something has to leak. If no external leaks are found, it is internal.

 

[79jasper]

Yes it will.
I've had a sinking pedal, adjusted my brakes and bam, no more sinking pedal.
No leaks anywhere.

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[Black dawg]

so, you push the brake pedal down hard, brake pads and shoes are firmly seated into the drums and rotors, and then the pedal starts to sink. Where does that fluid go?

 

[icanfixall]

so, you push the brake pedal down hard, brake pads and shoes are firmly seated into the drums and rotors, and then the pedal starts to sink. Where does that fluid go?

In this case you are correct but.. you mentioned that the pads and shoes are firmly set. Thats not the case when the rears are out of adjustment. I was not a believer either till I saw this happen. I'm not sure how once the master cylinder has pushed enough fluid to stop the truck by the fronts does it bypass somehow and continue to fill the out of adjustment rears. But it does just that.

 

[rwelli1001]

Note about rear adjusters. I was taught many years ago, They only work when you come to a complete stop going backwards.

 

[chris142]

i agree with blach dawg. a low pedal will be fixed with adjusting the shoes.but if your sitting at a light and the pedal sinks to the floor thats a leak. usually internal in the master or dumping the fluid into the booster

 

[Deezelcaddy]

Thanx to all for the very quick replies. I will adjust the shoes tomorrow and report back. I imagine it is the standard procedure? Jack up a wheel crank until there is drag and back it off a bit? Please don't laugh too hard but I always get this wrong, do I pull the screw driver down or pull it up to expand the shoes. I know it's 50/50 but I always seem to guess wrong. Thanx again for all the help.

 

[79jasper]

I adjust to a slight drag and leave it there.

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[icanfixall]

Please use a brake adjuster spoon. Its much easier to adjust the shoes with that tool. They are cheap at most auto parts stores. Because of the adjuster it will only be able to be turned one direction. To turn the star wheel on the adjuster the other direction you must push a small flat screwdriver in to push the lever away from the star wheel.

 

[Deezelcaddy]

Well, I fixed the brakes and everybody was right. The shoes were way in. Also, the right rear wheel cylinder was seeping a bit(left side replaced last fall). I cranked out the shoes and replaced the wheel cylinder and all is well with adequate exceptions. The left side parking brake cable froze up on me so it is getting replaced today. This is a job I hate, but it is the only remaining cable I haven't replaced. Any tricks or is it just pull your guts out till you get it to catch? Also, both the and and the brake lights are on. This will be the third time I replace the abs sensor. The sensors work for about 6mos and then fail. I buy everything at napa. Should I try a dealership part this time? There is a bit of gear grease puking from the port on the rear. Thanx all in advance for your help.

 

[icanfixall]

Happy you fixed the brake problem. Sounds like you had 2 issues. A bad wheel cylinder and out of adjustment brakes. And now a leaky axle seal and a bad parking brake cable. Getting those fixed will give you great brakes again for the vacuum booster type brakes. Sounds like we were both right and wrong on this one. Sinking brake peddle was due to a bad wheel cylinder AND.. Out of adjustment brakes. Nice find really. To recap.. If you have a tight brake system and the peddle sinks after stopping usually the rears are way out of adjustemt but can also be a wheel cylinder or master cylinder bypassing or leaking thru. Adjusting the rear brakes is the simple easy way of determining whats wrong. Its also the cheapest fix. If adjusting the rears correctly does not fix the sinking peddle look deeper for a bad master cylinder or leak in the hydraulic brake lines or wheel cylinders. These trucks have 3 flexible brake hoses and the calipers up front can leak out the cup seals. I think that covers most of it well.