no rear brake fluid pressure rear brakes not applying

[donald]

2002 f250 superduty 7.3. I am replacing rear brakes that have not worked sense i bought truck. I have determined that there is no brake fluid pressure by opening bleeder screw a little got brake fluid release from bleeder. With bleeder loose i pushed on brake peddle and no additional fluid came out. I replaced the master cylinder after bench bleeding and have no change. I am doing this with motor off ignition off.
I have looked at rear brake lines as much as possible and see no problems.
I just sold my property and need to fix this right and fast any help would be greatly appreciated.
Thanks Don
541-446-3249

 

[XOLATEM]

Get a helper and try it with the engine running...my guess...and I have not seen one up close...is the fluid has to go through an ABS module to get to the rear.

Other, more experienced and knowlegeable folks on here will probably give you a better answer on that...give it time.

Wishing you good luck on it.

 

[Jesus Freak]

In the olden days, I would say that you have to recenter the proportioning valve. But in that newer truck it almost certainly has something to do with abs stuff.

 

[donald]

update disconected the hard brake line from the rubber line going down to axle pushed on brake peddle no fluid came out

 

[Jesus Freak]

It's in the abs stuff.

 

[donald]

talked to dealer service tech said there is nothing in abs unit to block fluid. Said it might be air lock in abs or a blocked line recommended bleeding. going to try mighty vac first then get a friend and try that. we shall see what happens.

 

[gnathv]

I’d crack the rear line fitting at the master cylinder and check it there. If it’s there follow it down the line. It’s air locked somewhere.

 

[donald]

update. removed rear brake line from abs applied120 lbs air pressure to brake line at abs removed one brake line from rear caliper, left other old caliper together. only had a small amount of brake fluid come out less than an ounce. then just air. It might be an air block in abs unit i will try to get help tomorrow to manually bleed the abs and then the rest of system.
Thanks for all the responses. Hope this fixes it.

 

[donald]

update bleed both lines from master cylinder to abs unit both bleed ok. bleed both front brake lines going from abs to front brakes they bleed ok. can not get any fluid to bleed out of brake line from abs to rear brakes. tried motor off and on no differance other than it is easier to push pedal. brake pedal is firm.

 

[donald]

can not get any brake fluid or air from air hose to go through rear brake port of abs unit. front brakes bleed easily. Driving 200 miles to junk yard tomorrow to get used abs pump and module. I tried using a snapon obd2 diagnostic to self bleed abs and all it said it could do is run an abs test. We did that several times, it did turn on the pump for a short test but still would not let brake fluid through abs rear port. I have been fixing brakes sense 1976 and have never seen this. I thought that the abs unit could not block the flow of brake fluid but i guess i was wrong. This truck has a way of schooling me when i work on it. Sure wish previous owner had taken better care of this truck.

 

[Jesus Freak]

I really don't trust abs stuff. Especially the Chevy abs stuff, even back in the late 90s their abs thing was as big as their engine under the hood.

 

[donald]

well the one i just picked up from the junk yard seems to be the same in that i can not blow air through the rear brake ports on abs while on bench. I thought that the fluid can flow through the abs at all times. Does anybody no if that is true or not. I do not want to install if it is going to do the same thing.

 

[Rdnck84_03]

I have never had to do much with the abs on those trucks so I really don't have a definite answer to your question. I would guess that if they both act the same that it is unlikely that they are both screwed up.

I have been told that a shop scanner is required for abs bleeding but I am unsure of the truth to that. I have swapped the abs unit on one of mine and had no issues bleeding it with the pump and crack bleeder at wheels method.

James