Need an answer
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Need an answer
I have a 1992 F-250, 4x4 extra cab with a 1 ton suspension. The problem is I have no brakes. I have replaced everything possible, with the exception of the RABS valve. The pedal seems to bleed off and the truck will not stop. I have bled the system and the RABS valve and there is no air. Still the system feels like it has air in it. I have checked the booster rod adjustment, the rear brake adjustment, and replaced every item you can think of. Can the valve cause this system to have a soft pedal and a long travel and no stopping power? Any Ideas?
Cargo Master
Joined: Jul 2009
Posts: 2,538
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From: Des Moines
I don't know about the RABS valve causing the problem, but I'm willing to bet you still have air in the system, by what you're describing.
Did you do a COMPLETE system bleed? Meaning, is it all new fluid in the system, or is there still some of the old left? If the latter, do a complete system bleed/flush/fill. Bleed every brake until there's new, clean fluid coming out, even if you don't see any air bubbles. That's about the only way to be sure there's no air in the system after a bleed. Also make sure that you're using a hose-in-bottle set up, where you have a clear hose or tube attached to the bleeder screw, and the other end submerged in a couple of inches of brake fluid in a bottle.
You say you've replaced a bunch of parts- so, are you certain that they are properly sealed? If you've replaced bleeder valves on the calipers/wheel cylinders, are you sure you threaded them in correctly? These are easy things to overlook, and many bleeder screws are small/short enough that a cross thread isn't that noticeable if you've got a longer ratchet or wrench.
Did you do a COMPLETE system bleed? Meaning, is it all new fluid in the system, or is there still some of the old left? If the latter, do a complete system bleed/flush/fill. Bleed every brake until there's new, clean fluid coming out, even if you don't see any air bubbles. That's about the only way to be sure there's no air in the system after a bleed. Also make sure that you're using a hose-in-bottle set up, where you have a clear hose or tube attached to the bleeder screw, and the other end submerged in a couple of inches of brake fluid in a bottle.
You say you've replaced a bunch of parts- so, are you certain that they are properly sealed? If you've replaced bleeder valves on the calipers/wheel cylinders, are you sure you threaded them in correctly? These are easy things to overlook, and many bleeder screws are small/short enough that a cross thread isn't that noticeable if you've got a longer ratchet or wrench.
Posting Guru
Joined: May 2010
Posts: 1,146
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From: Central Indiana
My 0.02 USD worth . . .
I'll make this suggestion-
Power bleed the system with copious amounts of fresh fluid, using this pattern;
RR, LR, RABS, RF, LF. Plan to use at least a pint of brake fluid at each position that you'll dispose of. Do not recycle back through the system!! Seriously! I've seen it done by someone too cheap to buy enough fluid to do it right the first time.
You probably either still have air in the system or your MC, even though it's new, is bad. Just because it's new doesn't mean it's good.
I would unbolt the MC and pull it ahead enough to see behind it. It may be leaking into the PB booster, where you wouldn't see it.
Just my 0.02 USD worth. YMMV.
Ray
Power bleed the system with copious amounts of fresh fluid, using this pattern;
RR, LR, RABS, RF, LF. Plan to use at least a pint of brake fluid at each position that you'll dispose of. Do not recycle back through the system!! Seriously! I've seen it done by someone too cheap to buy enough fluid to do it right the first time.
You probably either still have air in the system or your MC, even though it's new, is bad. Just because it's new doesn't mean it's good.
I would unbolt the MC and pull it ahead enough to see behind it. It may be leaking into the PB booster, where you wouldn't see it.
Just my 0.02 USD worth. YMMV.
Ray
Postmaster
Joined: Aug 2005
Posts: 4,728
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From: Cleveland, TN
Did you replace the calipers? If so are you absolutely sure you got them on the correct side? I'm not trying to be a smart a$$ here, we had a thread yesterday with the same problem, it turns out he got the calipers on wrong.... Make sure the bleeder screws are on TOP!!
Good luck with it....
Good luck with it....
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The problem brakes
I have put everything on correctly and everything has been checked and rechecked and then checked again. I have pulled over a gallon and a half of fluid through the system with a power bleeder system. I have put an oversized bore master cylinder on and new booster. There are no leaks, and there is excellent flow to every wheel. I can take the drum off one side in the rear and have someone push the brake pedal slowly down. It gets 3/4 of the way down before it ever begins to move the shoes. The fronts do apply right away, but they have no stopping power. I have worked on cars for 30 years and have never run into a problem like this. I think there are gremlins in this one!
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
I just replaced all the brake lines on a '94 Ranger and recently did the same thing on my F150 and the two couldn't have been more different in terms of getting the brakes to bleed correctly.. despite the fact the basic brake systems are almost identical. The Ranger was dumb easy and needed no extra persuasion.. started bleeding at the back passenger side and worked around to the front drivers side.. 1 shot and done. The F150 needed several rounds and even then the peddle was soft and traveled excessively, the thing I found after some time living with it was that the rear shoes were too loose and snugging them up closer to the drums greatly decreased brake peddle travel and improved stopping power. The other thing to check would be if you have the front and rear lines connected to the correct output on the master cylinder, the front brakes need more fluid volume.
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I now have BRAKES!
Ok guys, First thanks for all of your suggestions and replies to my problem brake F-250. The answer was the RABS valve. I have been a mechanic for many years and have never had a problem with this before, but believe it or not, it was the valve. I took it apart to find the problem. When the brakes were applied, it allowed a bleed by thus causing the pedal to fall and not fully engaging the rear brakes. I installed it this morning and now it will stand you on your nose! I had a feeling it was the problem, but due to the cost of this little puppy, I hesitated until last. But it works. 
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