This definitely fixed my soft / fading pedal! Only takes about 2 minutes total. Installing new master cylinder had no effect whatsoever.

https://www.ford-trucks.com/forums/7...2-f-250-a.html



'94 crew cab dually 7.3

 

Interesting... I just pulled my fuse to kill the ABS, it works okay I guess, but it still ain't as stiff as I want it, I'll try this trick tonight. One thing that kinda bothers me tho, what's stopping the piston from moving back when the pedal is released, wouldn't the suction from the master cylinder do the same as the spring does? I'd be more inclined to just put in a solid steel plunger or something in there, so I know the valve ain't going nowhere, neither in or out.

 

I don't know-all I can say is this fixed the problem and I have a firm, solid pedal, finally.

 

I'll mess with it tonight, see what I can come up with... Will post results of course.

 

Make sure you don't have a vacuum leak at the booster.

 

Aight, removed the nut (32mm wrench is what it needs), pulled the spring, replaced it with 32-33 mm long sleeve of the same OD as the spring, then put it all back together - sleeve bottomed out the piston just a tiny bit before the nut jammed against the RABS body, so tis all good and tight now. Didn't drive her tonight, will do tomorrow, but it should be good.

 

My Dodge has rear ABS and it'll lock-up the rear end first in a panic stop. It's not horrible but it sucks.
My Cherokee has 4-wheel ABS and it works AWESOME!
Haven't had any brake or ABS problem with my '94 IDI or '97 PS; YET!

 

My issue with the RABS is that it's more of an anti-skid system, at least mine is - the moment it feels the rears locking up it dumps the pressure and stays this way till I let off the brakes, compared to the constant on-off-on-off action modern ABS systems have. Honestly, I'd rather have full braking power all the time and back off manually when needed, compared to the RABS doing its thing at random times and leaving me with just front brakes and reduced overall line pressure.

 

Tested it today, brakes work great, solid feel and no issues locking up on dry pavement, with the lovely axle hop that accompanies that. Just ordered hydroboost hoses today, will pick them up tomorrow and go for installing the thing on Friday, however with that beast in I may wanna have the RABS active once again... we'll see.

 

first of all the so called fix should be deleted from the forum
sorry but i do have an issue when someone posts on how to disable a safety device
if you cant afford to replace the valve you cant afford to own the truck
the rabs valve is an accumulator with a solenoid valve , if teh pedal is soft and sinks and it is traced to teh rabs valve , it has a bad solenoid valve
the rabs valve opens and closes to absorb some hydraulic pressure to allow the rear wheels to rotate and the allows full pressure to them again and repeats when wheel lockup is detected
rabs does not dump the pressure and remain that way until you release the brakes it does work very similar to modern abs it will pulse as long as wheel lock up is detected until the accumulator is full

 

Yes, that's just what I found out last night while searching the web for more info on the logic it uses. Also, I drove the truck today, both on dry and wet pavement, and as a result my RABS is again fully operational - with the worn out rear tires my truck is way too easy to get sliding, a bit easier than I feel comfortable with.

As for the statement that if I can't afford to fix the RABS then I can't afford to own the truck - I'm sorry, but that's about the most arrogant comment I've heard in a while.

 

All I can say is I know of many safety devices in the trucking industry that did not work like they were supposed to.

Anti Lock brakes on semi trucks killed quite a few drivers when they were first introduced.
The pulsing brake application heated the brakes to the point of failure in a very short time.
More than one case of trucks hitting the run off ramps in the Rockies, after the truck stopped then it started rolling backwards, if one wheel was locking and the rest were turning, the anti lock released the one that was holding and now the driver was running off in reverse.

That was 80's technology as well.

I also remember when the federal government first required brakes on the steering axle.
Icy road, touch the brakes and hold on for the following crash because the front tires locked up.

In a semi it is bad when the trailer is sliding.
When the rear tractor axles are sliding it is worse.
When the steering axle tires are sliding, you are totally without any control at all.
As long as the front tires are turning, you can save a rig

That was such an issue that trucks were retrofitted with a valve to disable the front brakes on wet or icy roads or the front brakes were disconnected.

That was 60's & 70's technology that also killed people.

Yes the anti lock brakes on modern vehicles is a safety device.
Some of the early anti lock systems, well they just did not work like they were supposed to and had the opposite effect.

Bottom line, when I push the brake pedal I am much happier if the rear brakes lock up than I am when the brake pedal goes to the floor.

 

thanks Dave....

We do all sorts of mods here and not all of them are recommended by the factory, strait pipes are technically illegal too. I've concluded that ABS is designed for people that are not familiar with the limits of their own vehicle. I've been in close call situations with my truck a few times and I know exactly how hard I can hit the breaks without locking the wheels. My brain works well as my ABS, thank you very much. I don't want a computer taking control out of my hands in a life and death situation.

My Dad's GMC has 4 wheel ABS and that thing nearly sent him off the road a few times now. One wheel locks while others don't, in one case it was the front that locked up when he had to hit the breaks in a turn. His own reaction time was the only thing that kept him from going in the ditch on the far side of the road. He saw what happened and released the breaks enough to regain steering and recover.

Just a few weeks ago we nearly hit a deer and as he described it, the pedal was like "mush". Pavement was firm and dry on a strait road and my truck with vacuum boost would have easily stopped in a shorter distance in the same situation. His has very powerful hydroboost with big discs and drums, but with the ABS the breaking distance is way longer.

Sorry, but if I ever get a truck with ABS....Shoot me. Or give me directions on how to disable the ABS/ESP. There were automatic seatbelts that were once required by law too and they were such a disaster that the law was repealed. Not all NTSB regulations are good ones, and when it comes to life and death, I will live with my own choices rather than have them taken away to give some one else peace of mind.

 

One of my friends has driven tanker truck (fuel) for 30 years or so. His brand NEW truck has anti-lock brakes and he says it's kind of scary on anything less than dry pavement, on ice/snow it is terrifying.
He drives Hwy 20 from Swet Home to Sisters almost everyday and it is one of the hairiest, steepest, crookedest pases around. I've only been on one pass myself that was worse.
If it weren't for his experience there would have been a tragedy by now.

 

the statement wasnt arrogance it is a time tested and proven fact
the RABS system works , i know i was with ford well before such technology existed and still with them
i also know that my crew cab duelly will swap ends on wet pavement without it working
when in traffic situations
here is an example
truck owner decides to save money and disable the rabs
he learns how to baby the brakes while driving it so not to lock up the rear wheels
until one day when the highway comes to a halt and there isnt time to baby those
brakes and the truck plows over a family in their subcompact 3 plus ton truck versus a 1900 pound car thats half as tall
so the family dies maybe ,but hey the truck owner saved money
and unless things have changed disabling a safety device is still a felony
just my two cents
and yes my 89 is no cherry but my safety equipement all works as designed
especially the rabs
it didnt work when i bought it and i went about correctling that as quick as possible
M.L.S.C. thats why i have an 89 i cant afford to upkeep a powerstroke so i dont own one