Odd brake issue

[rusty ol ranger]

86 bronco ii

I went from having very little brake...to no brakes...to decent brakes....and now a stiff as a rock pedal and atleast one...if not both front calipers stuck. I havent messed with them yet either.

I took it for a spin after some tweaking and noticed i had it floored in 5th at 45-50 and was losing speed (i had good brakes when i left,..on a dirt road)...so i hit the clutch and it came to a stop pretty quick. Limped it back home and noticed both front rims were very hot (passenger more so then driver).....and it would not roll at all even on a hill....but i got no pulling of the wheel or anything so it kinda seems both are tied up? Rear drums are cool as a cucumber. Brake warning light is on (but its been on...i think the parking brake pedal thats unhooked dont come totally up)

Lines and hoses are new to pretty new.

Is this a master cylinder issue? Or calipers? Or something else? Never had an issue like this...usually i have brakes or i dont...or one wheel sticks.

 

[Ranger850]

Both fronts sticking at the same time probably isn't the slide pins. It sounds like a release or check valve might be clogged/stuck. No signs of water in the Stop juice, right? Water in the break system will swell up the o-rings and any other petroleum based products in the system, causing the symptoms you described. Could aslo be debris or rust particles clogging up the system.

 

[rusty ol ranger]

Both fronts sticking at the same time probably isn't the slide pins. It sounds like a release or check valve might be clogged/stuck. No signs of water in the Stop juice, right? Water in the break system will swell up the o-rings and any other petroleum based products in the system, causing the symptoms you described. Could aslo be debris or rust particles clogging up the system.

Fluid looked good in the resivior. It was low initially and i topped off the resivior.

I seen the lines and shit were new but the bleeders on nothing looked messed with so i figured it needed bled initially when it was soft. I kinda figured as the pedal got better (and i added fluid) and moved it around it kinda bled itself but i think i was wrong.

Just curious...would a power booster cause this? I heard a hiss the other day that stopped when i played with the pedal...but now i dont hear that. But i still have power assist

 

[ericbphoto]

It’s something common to both sides on the frint. So I would suspect something with the master cylinder. If opening the bleeders relieves the pressure and allows the calipers to relax, then the calipers are good.

 

[rusty ol ranger]

It’s something common to both sides on the frint. So I would suspect something with the master cylinder. If opening the bleeders relieves the pressure and allows the calipers to relax, then the calipers are good.

Im going to try that next time im out there since i got the engine squared away.

 

[Uncle Gump]

Not sure I've ever seen a master do that... but it could. Is the top of the brake pedal sloppy? If the master stuck... slop in tip of pedal.

I'm thinking calipers stuck...

 

[bobbywalter]

check the wheel bearings and make sure they arent loose and binding the calipers. if the vac booster popped seems you would hear it and the fast idle ect....

 

[rusty ol ranger]

check the wheel bearings and make sure they arent loose and binding the calipers. if the vac booster popped seems you would hear it and the fast idle ect....

Yeah i got no signs of a vacuum leak. Which is why i was puzzled by the hissing i heard the other day. Ill jack it up and see if the hubs wiggle at all once i confirm its not the brakes.

Not sure I've ever seen a master do that... but it could. Is the top of the brake pedal sloppy? If the master stuck... slop in tip of pedal.

I'm thinking calipers stuck...

Doesnt seem to be. Theres like....maybe 1/4-1/2 inch of nothing then the pedal gets rock hard. Would that be enough slop to indicate the master cylinder?

 

[superj]

i had an issue on my jeep cherokee one time where the brakes were spongy and didn't stop the truck decently. i changed the master cylinder and then the brakes would slowly lock up as i drove around. turned out that the rod from the master to the booster was a hair to long and the booster needed replacing. something went bad in the booster which caused it to slowly apply a little pressure

i was always told to replace the master and booster together, and i have not ever done it, till that jeep. once i replaced them as a unit, i never had trouble with the brakes again.

 

[rusty ol ranger]

i had an issue on my jeep cherokee one time where the brakes were spongy and didn't stop the truck decently. i changed the master cylinder and then the brakes would slowly lock up as i drove around. turned out that the rod from the master to the booster was a hair to long and the booster needed replacing. something went bad in the booster which caused it to slowly apply a little pressure

i was always told to replace the master and booster together, and i have not ever done it, till that jeep. once i replaced them as a unit, i never had trouble with the brakes again.

Hmm.

Maybe i should do both if its not the wheel bearings or calipers. Ive only replaced one booster ever and it was on my 77 F250. The booster wasnt even bad the damn vacuum nipple broke and fell down inside it. Ran the old master though.

Anyhow...ill pry update this thursday or friday (assuming i get the chance to mess with it) with any more questions or findings.

I hate brake stuff.

 

[Uncle Gump]

Probably not...

Crack a line loose at the master and if you get a big squirt of fluid... the master is probably holding pressure in the system. If not... look for stuck calipers.

 

[rusty ol ranger]

UPDATE....
Pretty sure its the master cylinder and/or booster.

The pedal only comes up halfway unless you pull it, once the pedal is pulled up you can hear a hiss.

Im just gonna replace both.

 

[Shran]

If the booster pushrod is adjusted to long it will lock up the fronts and they will get hot… when it cools down they will unlock. Not sure if that’s even part of your issue but it’s something to check.

 

[rusty ol ranger]

If the booster pushrod is adjusted to long it will lock up the fronts and they will get hot… when it cools down they will unlock. Not sure if that’s even part of your issue but it’s something to check.

I didnt know you could adjust the booster pushrod?

Yes thats exactly the issue i had. It was locked up tighter then fort knox, yesterday after i sat for 2 days they were still locked (when i tried to push it) but the pedal was back to mush...but as soon as i started it and moved it under its own power they broke free...and i did many stops with it but couldnt get them to lock again.

But like i said, if you hit the pedal it comes up maybe 1/2 way, stops for a second, comes up a bit more then stops and you have to pull it back up manually...then you hear the hiss from the booster.

 

[Shran]

pull the master cylinder off and you will see a pushrod with an end that screws in or out. It’s supposed to be set to a specific length. I don’t recall what that length is but google or a chilton book if you have one would have that info.