I didn't bleed the RABS unit yet because I didn't know it was there. A lot of other people are telling me the same thing that it is located in the frame on the driver side of the truck. As far as the "very poor brakes" are concerned the pedal feels pretty decent. Its when you are driving is when it gets sketchy. You can push the brake pedal with all your force and it just takes a long time for the truck to stop. If you stomp the pedal the brakes don't even lock up or seem to grab, you kinda just coast to a long scary stop. One of my buddies said he thinks it may be the brake booster. Does that seem to sound like it could be the problem. The truck sat for like 8 months, I don't know if that makes a difference either.

 

if you pump the pedal 2-3 times, is the pedal hard to push after pumping?
if so, then you have a bad vacuum pump. if it is always hard to push, then you either have no vacuum or a bad booster.

to test the booster and pump, with the truck running, put a vacuum gauge in the vacuum circuit somewhere and see how much vacuum you have. for the brakes to work properly, you want at least 17 inches vacuum. then have someone step on the brake pedal 2-3 times, and see how far the vacuum drops and how long it takes to recover. it should not drop much, and should recover almost immediately. if not the pump is bad.

if the pump tests good, remove the line going into the booster and see if there is any difference in the way the pedal fells. with the line off the pedal should be very hard to push down.

 

i think its the vacc pump

 

When I had hard braking it was the vacuum pump also, seems to be a common thing on these.

 

mine did the same as his and i replaced the complete brake system new lines and everything lol i was a noob at idi's didnt know what a vacc pump went to lol

 

Dude, I did that exact thing also, new booster, MC, lines, calipers, lol.

 

atleast im not alone lol but yeah to bad the damned thing is lik 150 bucks

 

My truck seems to have the same problem but when I look for a part on Autozone.com this is the only part Im finding (ABS Hydraulic Unit)
Cardone Reman/ABS Hydraulic Unit (12-2026) | 1994 Ford F250 3/4 ton P/U 4WD 8 Cylinders K 7.3L Turbo Diesel | AutoZone.com
is this the part you guys are talking about.
Mine brakes fine at first then its like the power assist just goes away

 

Thats the rabs valve and heres the vac pumpList: Vacuum Pump - 1984 Ford F-250 | O'Reilly Auto Parts

 

Awesome thanks so where is this part at? near the master cylinder?I know I should just go out and look for it but its dark and raining.

 

it works off of the serpetine belt i beleive its in btween the alt and the a/c compressor if i am not mistanging you have to take the belt off then remove the vacc pump

 

You will need a puller to remove the pulley, its the same setup as the ps pump. Autozone has them for free with deposit.

 

Thanks guys, my tenioner pully was begining to squeal so I was going to have to remove the belt anyway.

 

Does the brake proportioing valve have any part in bleeding the brakes?
I have a similar issue, but I don't have that fancy RABS thing.
All new lines, calipers/pads, hoses, a known good used master cylinder and booster (Working great on previous truck), wheel cylinders and shoes.
The only thing I haven't replaced is the vacuum pump, but I have 2 used spares to try.
I have the same feeling in the pedal. I push it, and it's firm...but seems to take a looong time to stop.

 

Mines the same way i always chalked it up to ford brakes, my vac pump pulls 26"hg and i still don't have that stop om a dime and give you 9cents change feel