Trouble Bleeding Brakes -- Endless Tiny Bubbles
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Trouble Bleeding Brakes -- Endless Tiny Bubbles
Have a very frustrating problem trying to bleed the brakes on my F-350 after overhauling the rear drums. I replaced all drum hardware and lines (hard and soft) from the ABS back. (fronts were done last year)
When I bleed the system I get good fluid flow with no bubbles for about 10-20 seconds, then I get a very long stream of tiny bubbles for about 10 seconds and it goes away. Does it sound like I'm pulling air in from a connector? I've been up and down this thing a dozen times, run my fingers around the connections, etc... and I can find NO fluid leakage.
I'm pretty stumped. Any ideas? My pedal is spongy and it feels like I only have the disks in the front working.
When I bleed the system I get good fluid flow with no bubbles for about 10-20 seconds, then I get a very long stream of tiny bubbles for about 10 seconds and it goes away. Does it sound like I'm pulling air in from a connector? I've been up and down this thing a dozen times, run my fingers around the connections, etc... and I can find NO fluid leakage.
I'm pretty stumped. Any ideas? My pedal is spongy and it feels like I only have the disks in the front working.
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Joined: Aug 2018
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if your sure there are no leaks it has air trapped somewhere...what i do is open the rr bleeder the push peddle to the floor and close bleeder and let the pedal up and repeat, when you pump the pedal it can trap some air in high spots, then replete at each wheel
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Joined: Aug 2003
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From: Dallas, TX
It's possible that it's pulling in air from the bleeder threads. Those don't always make a good seal. When I bleed my brakes, I only crack it open just enough to get fluid just barely flowing. Any more than that and I can never get a good bleed.
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OK. I spent all day on this double-checking every connection. I think the bubbles were coming in from around the bleeders. I just barely cracked them open and it seemed to make a difference. Bled the entire system front to back and no difference in feel. The pedal is still soft and it takes two or three pumps to get decent pressure and then just sinks to the floor. It feels like I'm only getting about 25% brake. I'm about 99% sure there is no air in the system.
The only things I haven't replaced are master cylinder and booster at this point. Thoughts?
The only things I haven't replaced are master cylinder and booster at this point. Thoughts?
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Tuned
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From: State of Confusion
Sinking to the floor suggests a fluid leak. If it's not external, it could be a bad seal in the master.
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I'm betting your RABS valve is failing or has failed. The seals inside are bad and allowing fluid to leak past.
You can bypass it or pull the big 1_1/4" nut off of it, then remove the inner spring. Reinstall and bleed, then your pedal will return.
Just be sure all air is bled. Once you remove the spring, I understand it can't be reinstalled correctly.
You can bypass it or pull the big 1_1/4" nut off of it, then remove the inner spring. Reinstall and bleed, then your pedal will return.
Just be sure all air is bled. Once you remove the spring, I understand it can't be reinstalled correctly.
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RABS was already replaced when I did the fronts.
I didnt understand this part. You are saying to remove the spring to bleed, but once its removed it can't be reinstalled correctly? 
Once you remove the spring, I understand it can't be reinstalled correctly.
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From: Dallas, TX
Has the ABS valve been bled? It has a bleeder on it and should be done last, if I recall correctly.
Once when I bled mine, I skipped the ABS valve, and still had a spongy pedal. Bled it along with all 4 wheels again, and it's stronger than it's been since I've owned the truck.,,
Once when I bled mine, I skipped the ABS valve, and still had a spongy pedal. Bled it along with all 4 wheels again, and it's stronger than it's been since I've owned the truck.,,
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Has the ABS valve been bled? It has a bleeder on it and should be done last, if I recall correctly.
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From: Mexico, Missouri
But since you said you have changed it already, then I would try bypassing it. Was it a New RABS valve that was installed?
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