03 F250 SD braking problem!!
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Mountain Pass
Joined: Nov 2012
Posts: 112
Likes: 11
From: Hurst,Texas
03 F250 SD braking problem!!
I don't know what's going on maybe some body can shed a little light on this. If you hold the brake pedal down for a long period of time you can feel the pedal slowly go to the floor. So no problem I'll change the master cylinder bleed everything brand new fluid. Don't drive it much we let the sister in law drive it we'll I jump back into it the other day to go to Home Depot and once again I notice it still does it. Could the hydra brake booster be bleeding by or what's else could be causing this it's driving me insane. I really can't imagine the hydra booster causing a problem but it's new to me so I'm asking if any body has any ideas. I was thinking about bleeding the brakes again thinking there maybe there's air but I have run 2 bottles of brake fluid through how much more??
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
Likes: 1,678
From: Stephensville WI
If your pedal drops slowly while you hold pressure on the pedal, then you are losing pressure. Replacing the M/C often cures this, but the issue may also be a leaking line, a ballooning flex line, a leaking caliper or a leaking fitting.
Thread Starter
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Mountain Pass
Joined: Nov 2012
Posts: 112
Likes: 11
From: Hurst,Texas
I'll get under it this weekend and look at the rubber lines and have someone step on brake pedal. I looked at the calipers all of them seamed fine and no brake fluid residue anywhere. Thanx.
Thread Starter
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Mountain Pass
Joined: Nov 2012
Posts: 112
Likes: 11
From: Hurst,Texas
K I drove it all day long today. You can apply the brakes and hold them after about a minute or more the pedal starts going to the floor once it's all the way to the floor you can still hold the brakes and the truck doesn't move so this tells me that it's not a master cylinder problem but something to do with the hydra booster or power steering pump. Is it possible the power steering has lose it pressure valving. Another words it doesn't developed the pressure it needs to sustain the brakes and steering. I can push on the brakes HARD and it causes the engine to idle down like it getting bogged down then when I push on the pedal hard and turn the steering you can't turn the wheel unless you let up on the brake pedal. So could it be the power steering pump loosing the pressure or could it be the hydra booster valving messed up.
Elder User
Joined: Oct 2001
Posts: 544
Likes: 2
From: Jersey Shore Not Seaside!
No.
As far as brake and turn issues, that's common for this truck. There is a priority circuit in the hydroboost that controls how much pressure is split between the steering and the brake boost; brake wins.
Pedal drop is not effected by the hydroboost with the exception that a HB that would apply full force under any pedal movement would take you to full apply with a long travel.
A slow drop in pedal can only be from a leak, master cylinder seals bypassing, or a fault within the ABS controller. If you are loosing fluid, you have a leak. If fluid is not disappearing, you don't.
There is a check for the ABS controller and the instructions for testing it is in my facebook page.
But the ABS controller failure is pretty low.
Aftermarket sources of M/C have had some early failure issues, though.
If you are not loosing fluid I would do the ABS controller check as that costs nothing but time. It's not uncommon to find that if you apply the pedal hard and hold the pedal holds, while a light application results in pedal drop is a good indicator of the M/C seals.
As far as brake and turn issues, that's common for this truck. There is a priority circuit in the hydroboost that controls how much pressure is split between the steering and the brake boost; brake wins.
Pedal drop is not effected by the hydroboost with the exception that a HB that would apply full force under any pedal movement would take you to full apply with a long travel.
A slow drop in pedal can only be from a leak, master cylinder seals bypassing, or a fault within the ABS controller. If you are loosing fluid, you have a leak. If fluid is not disappearing, you don't.
There is a check for the ABS controller and the instructions for testing it is in my facebook page.
But the ABS controller failure is pretty low.
Aftermarket sources of M/C have had some early failure issues, though.
If you are not loosing fluid I would do the ABS controller check as that costs nothing but time. It's not uncommon to find that if you apply the pedal hard and hold the pedal holds, while a light application results in pedal drop is a good indicator of the M/C seals.
Thread Starter
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Mountain Pass
Joined: Nov 2012
Posts: 112
Likes: 11
From: Hurst,Texas
WOW I appreciate it very much this give me somewhere to start because I thought the same thing MC bypassing so replaced that immediately. But the basic problem was still there so now I'll chase the ABS controller. Thanx. I'll let y'all know what I find.
No.
As far as brake and turn issues, that's common for this truck. There is a priority circuit in the hydroboost that controls how much pressure is split between the steering and the brake boost; brake wins.
Pedal drop is not effected by the hydroboost with the exception that a HB that would apply full force under any pedal movement would take you to full apply with a long travel.
A slow drop in pedal can only be from a leak, master cylinder seals bypassing, or a fault within the ABS controller. If you are loosing fluid, you have a leak. If fluid is not disappearing, you don't.
There is a check for the ABS controller and the instructions for testing it is in my facebook page.
But the ABS controller failure is pretty low.
Aftermarket sources of M/C have had some early failure issues, though.
If you are not loosing fluid I would do the ABS controller check as that costs nothing but time. It's not uncommon to find that if you apply the pedal hard and hold the pedal holds, while a light application results in pedal drop is a good indicator of the M/C seals.
As far as brake and turn issues, that's common for this truck. There is a priority circuit in the hydroboost that controls how much pressure is split between the steering and the brake boost; brake wins.
Pedal drop is not effected by the hydroboost with the exception that a HB that would apply full force under any pedal movement would take you to full apply with a long travel.
A slow drop in pedal can only be from a leak, master cylinder seals bypassing, or a fault within the ABS controller. If you are loosing fluid, you have a leak. If fluid is not disappearing, you don't.
There is a check for the ABS controller and the instructions for testing it is in my facebook page.
But the ABS controller failure is pretty low.
Aftermarket sources of M/C have had some early failure issues, though.
If you are not loosing fluid I would do the ABS controller check as that costs nothing but time. It's not uncommon to find that if you apply the pedal hard and hold the pedal holds, while a light application results in pedal drop is a good indicator of the M/C seals.
Posting Guru
Joined: Jan 2013
Posts: 2,215
Likes: 2
From: North Lake Tahoe
Correct me if i'm wrong, but can't old and dirty power steering fluid play in affect to this. I heard that by flushing out the power steering fluid with 3 to 4 qts of oil can play a huge roll on the braking system. If your truck has many miles and have never changed the steering fluid it couldn't hurt. Trey did a nice youtube video on how to do it.
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Fleet Owner
Joined: Apr 2012
Posts: 27,307
Likes: 549
From: Spanaway
If the hydroboost was the problem you would not have a sinking peddle.
You would be getting a still peddle.
With the engine off push the peddle down. Does it still sink?
That fluid is going somewhere. Rubber flex lines can be the first
place and then there is leaking rotors or the master cylinder is
leaking internally. Last but not least is the ABS controller.
Fmtrvt gave you a good document to start with.
I agree that some of the less costly rebuilt master cylinders
are not holding up well. We depend on these trucks to do
heavy work and when it comes to stopping. Save a life and
don't go cheap.
Sean
You would be getting a still peddle.
With the engine off push the peddle down. Does it still sink?
That fluid is going somewhere. Rubber flex lines can be the first
place and then there is leaking rotors or the master cylinder is
leaking internally. Last but not least is the ABS controller.
Fmtrvt gave you a good document to start with.
I agree that some of the less costly rebuilt master cylinders
are not holding up well. We depend on these trucks to do
heavy work and when it comes to stopping. Save a life and
don't go cheap.
Sean
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Fleet Owner
Joined: Apr 2012
Posts: 27,307
Likes: 549
From: Spanaway
The one other cause of a sinking peddle is a bad master cylinder.
At least that is where I would look with all you have done so far.
If you don't mind paying for the service you can get the manuals
at one of two places.
https://www.motorcraftservice.com/vd...p?menuIndex1=1
And
ALLDATA - OEM Auto Repair Information for Professionals
If you go this route then spend all night downloading everything to you hard drive.
That way you have it for later.
Sean 
At least that is where I would look with all you have done so far.
If you don't mind paying for the service you can get the manuals
at one of two places.
https://www.motorcraftservice.com/vd...p?menuIndex1=1
And
ALLDATA - OEM Auto Repair Information for Professionals
If you go this route then spend all night downloading everything to you hard drive.
That way you have it for later.
Sean
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