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Brake Bleeding With RABS

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Old 08-18-2013, 02:16 PM
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Brake Bleeding With RABS

98 F-150, rear drums, discs. on front. Replaced all rotors, drums, pads and shoes. Still has a low brake pedal and a little spongy. Rears are adjusted correctly, so that is not it. I pulled the back two cylinders and under one cup it was wet, so I replaced that one. Bled it correctly the old fashioned 2- man method....(OK....wife and I), RR then LR....got all the air out. It is better....but being the old **** guy I am...not quite right. A year ago the RABS module for the rear only ( located right under the MC) corroded off the terminals, so I tossed in a used one and got the ABS light to go off. I did the quick bleed by cracking the line from the ABS module that takes off to the rears. It was "OK" but I always felt it was a little mushy. It has a bleeder on it, so my question is do you bleed the RABS first then the back two wheels? That would seem to make sense. Since it is rear only there is no "motor" in the RABS unit that would have to be activated to bleed them. As always, any input is appreciated.

Jeff
 
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Old 08-18-2013, 02:36 PM
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Originally Posted by Spotty
98 F-150, rear drums, discs. on front. Replaced all rotors, drums, pads and shoes. Still has a low brake pedal and a little spongy. Rears are adjusted correctly, so that is not it. I pulled the back two cylinders and under one cup it was wet, so I replaced that one. Bled it correctly the old fashioned 2- man method....(OK....wife and I), RR then LR....got all the air out. It is better....but being the old **** guy I am...not quite right. A year ago the RABS module for the rear only ( located right under the MC) corroded off the terminals, so I tossed in a used one and got the ABS light to go off. I did the quick bleed by cracking the line from the ABS module that takes off to the rears. It was "OK" but I always felt it was a little mushy. It has a bleeder on it, so my question is do you bleed the RABS first then the back two wheels? That would seem to make sense. Since it is rear only there is no "motor" in the RABS unit that would have to be activated to bleed them. As always, any input is appreciated.

Jeff
I can't answer your question 100%, but I have always heard it should be in this order.. RR, LR, RABS, RF, LF.. Thats the way I have always done it and haven't ever had a problem.
 
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Old 08-18-2013, 02:40 PM
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Yeah...been bouncing around the 'brake section" here and that seems to be the answer. Maybe I'll wait for some more input before I bleed the RABS. Thank You for the response !!
 
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Old 08-18-2013, 04:11 PM
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I went out and looked on the RABS module and there was a nipple on the side of it.....bigger than what you see on a wheel cylinder. It had a rubber cap on it that I pried off. It took a 24mm socket to loosen it and nothing runs out even when hitting the pedal. So I took it out and behind it was a spring that puts some pressure on that cap and nipple. It was clean and not plugged. I screwed it back in and I am leaving it alone since I have no clue if that should bleed or what....
 
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Old 08-20-2013, 09:02 AM
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Beside bleeding you might want to recheck your rear lining to drum clearance. If they're too far apart it requires more pedal stroke to supply more brake fluid to the rears.
 
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Old 08-20-2013, 09:21 AM
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Originally Posted by Lime1GT
Beside bleeding you might want to recheck your rear lining to drum clearance. If they're too far apart it requires more pedal stroke to supply more brake fluid to the rears.
Yeah...that's how it acts. I ran the star adjuster tight to center the brakes in the drums, then backed it off to a slight drag.....I think that is OK. Actually yesterday the pedal felt higher and firmer, so maybe as the pads and shoes "wear in" it will get better. This is my work truck and I will admit it is overloaded with construction stuff, tools, a rack, ladders....etc. Brakes have always been more of a "suggestion" than a "command"...Thanks for the input though...
 
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Old 12-05-2013, 07:03 AM
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Did your pedal ever become firm?

I've got a new-to-me '98 with the RABS, and can't get a firm pedal after flushing a quart of fluid through the system.
 
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Old 12-05-2013, 01:37 PM
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A squishy break pedal is a common problem on the older f150's 97 to i think about 99. from what i have found there is really no fixing this problem. i had a 97 4.6l and from the day i bought it it had a soft pedal. and i know of and have driven several other older f150's with the same problem. Even after putting all new pads and running all new break lines they were still the same. from what i know there is not a fix. but maybe someone will chime in with a better answer.
 
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Old 12-05-2013, 04:52 PM
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I have a 1997 F-150 4x4 4.6L I have replaced everything except a few front brake lines, and my pedal has ALWAYS been soft. I've replaced front calipers and pads, rear wheel cylinders and shoes, rear brake lines from the master cylinder back, and nothing has improved my pedal feel. The truck stops fine, just has a soft pedal.
 
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Old 12-07-2013, 07:50 PM
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Originally Posted by BobBarry
Did your pedal ever become firm?

I've got a new-to-me '98 with the RABS, and can't get a firm pedal after flushing a quart of fluid through the system.

Yes...it eventually got firmer and higher...took a few weeks. Have no idea why...Maybe the rear drums got centered in and "fit" better after a few hundred stops.
 
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Old 12-07-2013, 08:50 PM
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I adjusted the drums outa bit, and it's better than before.

There doesn't seem to be any provision or procedure to bleed the rear ABS unit, so it isn't likely that.
 
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