Brakes?/ Help??
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New User
Joined: Jul 2017
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From: Texas
Brakes?/ Help??
03 F250 7.3. I busted a brake line last week somehow, Got it replaced and fixed up, Bled that line and everything was somewhat good.
Now, when i hit the brakes hard, I have pressure. If I let off even a little, My pedal will start to sink till i apply more pressure. Any opinions on what i should do? I am gonna fully bleed my brakes when I'm home to see if it helps any.
Any past experiences from anyone will be great
Now, when i hit the brakes hard, I have pressure. If I let off even a little, My pedal will start to sink till i apply more pressure. Any opinions on what i should do? I am gonna fully bleed my brakes when I'm home to see if it helps any.
Any past experiences from anyone will be great
Hotshot
Joined: Jul 2008
Posts: 12,782
Likes: 2,142
From: N.GA Mountains
The MC typically never travels beyond 1/2 pedal. When you push pedal to floor it forces the piston into places in the cylinder it doesn't normally go. If there is corrosion on the cylinder walls, it can damage the piston seal and allow MC to 'bypass' causing what you describe.
When I bleed brakes, I put a block of wood under the brake pedal to prevent full travel and avoid this problem.
When I bleed brakes, I put a block of wood under the brake pedal to prevent full travel and avoid this problem.
Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
I'm going to point in a slightly different direction and say you have air in the lines.
An example: Recently I was replacing both rear lines and the center "feed" line and block to those lines.
Well, I replaced both lines first and bled them. Then when I replaced the center feed line, I had to disconnect those and there were some other access issues that allowed the lines to drain.
I allow the lines to drain slowly (tie them up) when disconnected, but make sure to never let the under the hood reservoir go too low (avoid master cylinder bleed issues)
When all was reassembled, I bled the lines again. But on the test drive had similar issues as you describe.
There was air further back in the line that took a lot more fluid to bleed out, but it was obvious once the air hit the bleeders.
Since you had a brake line actually BREAK, it's likely you had a pretty significant drain of fluid and also likely you simply have air further up the line. Bleed the farthest brake from the MC first.
Is it possible to have a failed MC? Sure, but I'd bet it's just air
Good luck and let us know what you find!
An example: Recently I was replacing both rear lines and the center "feed" line and block to those lines.
Well, I replaced both lines first and bled them. Then when I replaced the center feed line, I had to disconnect those and there were some other access issues that allowed the lines to drain.
I allow the lines to drain slowly (tie them up) when disconnected, but make sure to never let the under the hood reservoir go too low (avoid master cylinder bleed issues)
When all was reassembled, I bled the lines again. But on the test drive had similar issues as you describe.
There was air further back in the line that took a lot more fluid to bleed out, but it was obvious once the air hit the bleeders.
Since you had a brake line actually BREAK, it's likely you had a pretty significant drain of fluid and also likely you simply have air further up the line. Bleed the farthest brake from the MC first.
Is it possible to have a failed MC? Sure, but I'd bet it's just air
Good luck and let us know what you find!
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New User
Joined: Jul 2017
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From: Texas
I actually think I found the issue folks. It is the master cylinder. It had a very subtle leak right by the fire wall. Not even enough to make a puddle on the concrete but enough to let it suck some air
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Senior User
Joined: Jul 2017
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From: Yuba City
With anything hydraulic, cleanliness is next to godliness. This finds very near an original or seal is all over.
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