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84 Brake issue

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Old Sep 7, 2020 | 09:32 PM
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84 Brake issue

Hey all, I’m looking at buying an 84 250 with the 6.9. The brakes are spongy at best, and that’s after being bled four times. Not sure what’s going on but I’d like to have an idea before I buy it. I’ve been looking at new brake lines for it all evening. Any input on where to start looking would be most appreciated. Thanks all!
 
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Old Sep 7, 2020 | 09:48 PM
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master cylinder is my first guess
 
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Old Sep 7, 2020 | 09:51 PM
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“Supposedly”, that was replaced within the last couple years. Not certain if it’s the booster or what. Did the diesel 250s have a heavy duty braking system?
 
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Old Sep 7, 2020 | 10:40 PM
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well just do the Booster trouble shooting and I'm pretty sure you will discover that boosters do not cause spongy brakes
 
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Old Sep 8, 2020 | 08:32 PM
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If you decide to replace the master cylinder buy one for a F-350.
 
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Old Sep 8, 2020 | 08:36 PM
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Originally Posted by Perk85F250
If you decide to replace the master cylinder buy one for a F-350.
forgive me, I’m completely new to this. It’ll bolt up directly?
 
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Old Sep 8, 2020 | 10:00 PM
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On my 91 f250 it always had spongy brakes ever since I bought it, but they worked great, eventually it was got pretty bad and the pedal was pretty low to the floor. Ended up adjusting the rear brakes and although they do still feel spongy, they work absolutely fine.
 
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Old Sep 8, 2020 | 10:07 PM
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Originally Posted by 84_6.9
forgive me, I’m completely new to this. It’ll bolt up directly?
Yes, direct replacement.
 
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Old Sep 8, 2020 | 10:51 PM
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I think a bit of the Sponginess comes from the Accumulator in the RABS unit on the 91 .. I see it a bit on my 93 also

that didn't happen with my 83 or 84
 
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Old Sep 9, 2020 | 10:03 AM
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Originally Posted by lonewolf_
I think a bit of the Sponginess comes from the Accumulator in the RABS unit on the 91 .. I see it a bit on my 93 also

that didn't happen with my 83 or 84
Leads me to suspect the rear wheel cylinders then. On a daily driver they will normally start leaking fluid when they're shot. But on something that's sitting alot of times they'll hold fluid but suck in air...
 
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Old Sep 12, 2020 | 11:33 PM
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The accumulator - you mean the chamber in the RABS valve with the Spring in it?
 
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Old Sep 13, 2020 | 11:11 AM
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Originally Posted by Mwdog
The accumulator - you mean the chamber in the RABS valve with the Spring in it?
Correct. see image
 
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