[Winston1984]

Hi all, long time user but my mail account to recover password got nuked.

Been working on this problem for months intermittently. 96 f250 4x4, Dana 60 swapped in. I’ve had this truck about 4 years. Brakes were never great but never felt unsafe till recently.

Pedal will sink to floor after hitting an initial hard spot. I knew my backs were in bad shape so totally rebuilt the back end(minus one wheel cylinder but it’s not leaking) replaced master as it was seeping into booster. Bench bled the master, then ran a gallon attempting to bleed air out. Not getting any air. Even found out about the rabs, bled that. Did some panic stops to try to actuate and rebleed rears in case it cycled air in. Found an old post here about air trapped in the calipers.

No dice. Pedal still sinks to floor over a second or so. I could use y’all’s help as I’m at my wits end.

 

[klhansen]

It's possible the replacement master was bad out of the box. Not an unusual occurrence.
Something is leaking by in the master cylinder for the pedal to go to the floor. There's really no other explanation for that symptom. It wouldn't be air, that would just cause a soft pedal till the air gets compressed, but the pedal wouldn't go to the floor.

 

[Winston1984]

Thanks kL,I was suspecting that but was unsure. Are any brands worth anything? This is a raybestos from rockauto. Is there an oem solution?

Like everyone, I just want a decent part the first time.

 

[Steve83]

96 f250 4x4, Dana 60 swapped in. I’ve had this truck about 4 years.

You should put ALL the truck's details & history (as much as you know) into your signature so it shows with each post, as this page explains:

(click this text)


Phone apps don't always show signatures, so you may need to switch to a real browser in desktop mode on your phone, or just use a desktop/laptop computer. Put your location (nearest city) in your profile & upload an avatar of the truck. The more pics you post of the truck, engine, wiring, labels, & undercarriage, the more likely we can help you. Not all its details are relevant to these issues, but you don't necessarily know which ones are relevant, so just put everything in now.

...totally rebuilt the back end(minus one wheel cylinder but it’s not leaking) replaced master as it was seeping into booster. Bench bled the master, then ran a gallon attempting to bleed air out. Not getting any air. Even found out about the rabs, bled that. Did some panic stops to try to actuate and rebleed rears in case it cycled air in. ... Pedal still sinks to floor over a second or so.

Got any pics of what you did? List of parts you used? Did you follow the Ford instructions for assembly, including grease? Read this page:

(click this text)


What about the front wheels? Are the bearings maintained & adjusted properly? If they're loose, the brakes must first straighten the rotors before they can begin braking, which will also result in a low (or no) pedal.

 

[Winston1984]

Steve83. Understood on profile. Like said, I gave up on my old account and created this one. Will flesh out details in bio. Truck is my electrical contracting truck. Bought it, rebuilt the ttb front end. 100k later the front needed rebuilt,almost every component. Bought a salvage 60 and put new front components including brakes and calipers 30k ago. Work done as link showed. I did not replace the drums, I should take back off and confirm measure. The adjusters were run out to light contact as indicated. Also ran them out further for testing purposes. No change in pedal. Good point on wheel bearings-confirmed they are in spec.

Mororcraft shoes, hardware kit, and driver adjuster kit. Don’t remember brand of wheel cylinder.

 

[bugman]

I can't do it but Kevin should be able to recover your old username. Just send him a PM with what it was along with your new email address

Sent from my SM-A426U using Tapatalk

 

[1997VAstroker]

My buddy had a similar issue with his old Cherokee, beat him up for months. Finally took it to a friend of ours garage. It beat them up for awhile too. Ended up that the rear shoes were out of adjustment. They seemed in spec buy spinning the wheel by hand, but under use caused the pedal to travel to far and he would run out of brakes. his pedal was solid when it had no Vac assist (Vehicle not running). Not saying this is what you have, but you might want to check the shoes a second time.

 

[mwaters_120]

Vacuum pump is possibly bad , you have vacuum assist pump on the truck , get a vacuum gauge to check hose at booster from the vacuum pump .

 

[Winston1984]

Vacuum pump is possibly bad , you have vacuum assist pump on the truck , get a vacuum gauge to check hose at booster from the vacuum pump .

That would give me a hard pedal correct? Or are you saying it’s weak and taking time to build-which reveals a bad hydraulic sustfm

 

[mwaters_120]

That would give me a hard pedal correct? Or are you saying it’s weak and taking time to build-which reveals a bad hydraulic sustfm

No pedal It will be soft go right to floor , I checked the vacuum on my 95 F350 and it was well under 10 psi , new vacuum pump was the fix

 

[Winston1984]

Will check vacuum pump when I get home. However that goes against what I understand about brake boosters. Unless there is a failed mechanical(linkage) component it should be giving no boost, therefore no assist. Or am I wrong?

On my super duty for example: hydro boost. Say you leave your foot on the brake pedal and shut the truck off. After the accumulator expels the reserve the pedal gets stiffer and rises a little. My old squares with vac. boosters do it as well.

I appreciate all suggestions

 

[Donald Lewis]

Steve83. Understood on profile. Like said, I gave up on my old account and created this one. Will flesh out details in bio. Truck is my electrical contracting truck. Bought it, rebuilt the ttb front end. 100k later the front needed rebuilt,almost every component. Bought a salvage 60 and put new front components including brakes and calipers 30k ago. Work done as link showed. I did not replace the drums, I should take back off and confirm measure. The adjusters were run out to light contact as indicated. Also ran them out further for testing purposes. No change in pedal. Good point on wheel bearings-confirmed they are in spec.

Mororcraft shoes, hardware kit, and driver adjuster kit. Don’t remember brand of wheel cylinder.

Running out to light contact does not mean they are close. Run them brakes shoes out to lock the wheel gettinig them centered, then back of for moderate drag.

If that replacement master cylinder was A-1 Cardone brand expect it not to work.