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Discussion Starter · #1 ·
My brakes were working fine, hadn't had any work done on anything, was out with my lawn equipment and trailer and came to a stop sign....surprise....VERY soft brake pedal all of a sudden! It's been that way for almost 2 years - I've gotten used to it. I still have full use of braking, it's just that I have to go almost to the floor to get it!
I have a 2001, F250, 4 Door, XLT, 7.3 Diesel, 2 wheel drive, I THINK it's 4 wheel ABS (It has an ABS sensor on the front, not the back), 333,000 miles. I haven't had any brake work done on it since 2013, and even then it was only new pads.
I've been told it was probably the ABS pump, which I've found on EBay for anywhere from $99 to $460 used, but, before I buy one, I want to make sure that that is the culprit. Could it be the hydroboost? I just replaced the power steering pump about 2-3 years ago. What about the master cylinder? Brake booster?
If I pump the pedal it gets stiff but then goes limp again after a few seconds.
From what I understand, it's probably the ABS pump bypassing.
Is the ABS pump the same as the HCU?
Thanks!
Jim
 

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Experts will chime in, but sounds like the master cylinder to me.


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If I pump the pedal it gets stiff but then goes limp again after a few seconds.
This is a classic sign of master cylinder bypassing. There are two chambers (front and rear) separated by rubber cup seals. If the fluid bypasses the seal from one chamber to the other, the pedal will sink as the fluid bypasses back to the reservoir.

From what I understand, it's probably the ABS pump bypassing.
Negative, Ghost Rider. Unless it has an external leak, the ABS pump can't cause the pedal to sink.

Unlike the master cyl (which vents to the reservoir), the ABS module has no passages to the outside. There are two inputs from the master cyl, and three outputs to the calipers. Basically, the 5 pressures are all identical when you step on the pedal (NON-abs assisted stop). Even if there are internal leaks between passages, the pressures will still be equal, and the pedal won't "sink", because no fluid is being displaced.
 

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I've had the same problem for a few years on my wifey's F150.
Had a dealer change master , all fluid, pads everything - no help.
Then after a while it started getting worse.

After some research I came across this thread and post #20 outlines how to check an ABS hydraulic control unit.
https://www.ford-trucks.com/forums/970862-2002-f150-brake-pedal-fade-2.html
I changed the ABS hcu and all is back to normal

I dont think it's quite the same on our super duties, but it's a good place to start looking after the obvious has been checked, ( ie, leaks, air in lines, etc.)
 

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i would be changing master cylinder first, cheaper, easier to change, and most likely the cause of your problems shy of a caliper leaking.
 

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Discussion Starter · #6 ·
Not the master...

Well, I replaced the master cylinder today with a brand new one from O'Reilly's (not reman'd) after bench bleeding it (quite easy to do with a very long extension for sockets, btw!), bled the brakes (got the old cruddy fluid out), and nothing has changed. I still have a good solid pedal at first, then it slowly drifts down towards the floor.
Next? Booster? I saw a post about the ABS hydraulic control unit - is that the same as the pump or different? Initially that's what I thought it was (the hcu).
There are no leaks anywhere, so that cuts that out of the equation.
I'm open to suggestions....
Thanks for everyone's support!!
Jim
 

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I'll be damned. I was sure a master cyl would fix it. The post linked above is for the F150 which evidently has a return line to the master cyl. I didn't think the early Super Duties do. I'll look at my 99 tomorrow in daylight. If you do want to try the "paperclip test" outlined for the F150, I would suggest removing the LF inner wheel house panel to access the HCU. It's under the left battery, and even if you remove the battery and tray, its a long reach down there. Through the wheel well its right there.

If I led you astray, I apologize.

Edit add: Just for grins, have you attempted to make the ABS activate? Make sure there's no one behind you, and there's nothing to hit if it brake-pulls unexpectedly, and stand on the brakes. See if the ABS works. And perhaps something in it wlll get dislodged, or "reset" by the activity. I have no idea if it will or not. But sure won't hurt anything to give the ABS a work out.
 

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Discussion Starter · #8 ·
Hey Dave, thanks so much for all the help so far! It's greatly appreciated! While I'm no expert around an engine or vehicle, I usually know enough to fix things but this has me stumped!

So here's where I stand currently: Like I said, I replaced the M/C the other day and there was no change. Today I disconnected the two lines from the M/C and plugged them. I started the truck and stepped on the pedal and it went down pretty much to the floor and I started getting a kickback. I stepped on it several times to see if anything would change and it didn't. I then shut the truck off, put the lines back in place and started the truck again and this time I definitely felt kickback and the pedal went to the floor quickly. I ended up having to bleed all the brake lines manually, the old push and hold way with my partner (the first time I bled them I used a mityvac).
After bleeding the brakes a LOT, I got it back to about where I was before I plugged the M/C today. The one thing that has changed now is that the brake light is now on all the time, where it wasn't before I did anything with the M/C today. I also feel a kickback on the pedal.
To answer your other questions: No, I haven't tried activating the ABS pump on a dirt/gravel road yet....we don't have too many around here but I'm watching for one so I can do just that to see if it does anything. On the same note, I just realized today, after 5 years of owning this truck, that when I turn the key on and give it a few seconds, there is what almost sounds like a vacuum release or something under then hood. I found out today that it's the ABS activating or doing something. Is that normal? Is that good/bad?
I will try to do the paperclip test this weekend if I get a chance - I have a big job to do tomorrow so it may be Sunday.
On a side note, after I bled the brakes today, I drove it down my street, only doing about 25-30 and slammed on the brakes. They definitely grabbed, as I could hear the screech of the rear wheels locking up.
So, with plugging the master cylinder and the pedal going to the floor - does that mean the m/s is bad?
Thanks again!
Jim
'01 F250 XLT 4 Door 7.3 Powerstroke with 333,000. Still going strong!
Go FORD :)
 

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This guy is our resident brake guy. He has done a brake job or 2 in his day. @zsargent
 

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I don't think the M/C is bad However it is possible. I have seen more master cylinders being damaged on the bench because ppl go too hard on them. I just like to gravity bleed them first. Take longer for sure but no risk of tearing a cup.

I would check all your lines. have someone push the pedal and hold it. Check any soft brakes lines (both front and one rear) for bulges. Inspect very carefully and report.

Check all your calipers, anything leaking. did you notice any loss of brake fluid before? Also do you have drums in the rear?

You have a leak somewhere. Gotta find it.
 

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@zsargent

I mentioned in post 4 above about an ABS HCU on my wifes F-150.
Do we have one on our superduties ?
 

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@zsargent

I mentioned in post 4 above about an ABS HCU on my wifes F-150.
Do we have one on our superduties ?
There is definitely a HCU on the 2002 with ABS. Not sure if the paper-clip test will work... ?

Attached are some service manual pages for the 2002...
 

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Discussion Starter · #13 · (Edited)
Thanks zsargent. I'll check the lines but I don't have any leaks. It wasn't leaking before the new master and it's not leaking now. I'm not losing fluid and really haven't had to fill the resevoir. I'll see what I can do with it tomorrow. I have to work on a job today and am doubtful I'll have time to do anything about any of it.
I have 4 wheel disc.
Jim
 

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Discussion Starter · #15 ·
I've been looking everywhere as to how to do the paperclip test and I have a pretty good idea now but do I have the engine running or off when I do the test? Thanks!
 

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Here is the link again....http://redirect.viglink.com/?format...www.ford-trucks.com/forums/9...al-fade-2.html
go to post #20 for explanation.

Engine running and you'll need a helper to depress the brake pedal when you have the paper clip in the hole.
If it moves more than a 1/4" (which is not much) then HCU has failed.

When I did my F150 the paperclip moved about 1 full inch in one hole and 3/4" in the other.
 

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Discussion Starter · #17 ·
Well, I finally got around to doing the paperclip test on the abs pump today and failed miserably! The first port i put the clip into was fine but the other one just about pushed the paperclip all the way out of the hole!
I've found a replacement on ebay out of Utah and it'll take about 10 days to get.
Will I need to take the truck to the stealership to have them activate the pump to get the air out of the pump after i get it installed and everything bled again?
Do I have to have something reprogrammed so it'll see the different pump?
Hopefully this works - the pump was only $50 with free shipping but this is getting to be like a witch hunt!
Thanks for your help gents!
Jim
 

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Sorry for late reply.
I had a shop do the bleeding because there is a special procedure for these ABS units.

Did you have any luck with this yet @AtlJim965 ?
 

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Discussion Starter · #19 ·
Hey guys, sorry for taking so long to reply!
I put in the reman'd abs pump that i bought off of ebay for $50 and I now have brakes close to what they should be!! My brake light is still on but I'm going to return this master cylinder and get a new one....i may have damaged it when i plugged the ports, started the engine and applied pressure to the brake pedal.
As of right now, i have a good pedal and it doesn't sink but i think it should be and was firmer!
At least i have fresh brake fluid in the system now! Lol!
 

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This is a classic sign of master cylinder bypassing. There are two chambers (front and rear) separated by rubber cup seals. If the fluid bypasses the seal from one chamber to the other, the pedal will sink as the fluid bypasses back to the reservoir.


Negative, Ghost Rider. Unless it has an external leak, the ABS pump can't cause the pedal to sink.

Unlike the master cyl (which vents to the reservoir), the ABS module has no passages to the outside. There are two inputs from the master cyl, and three outputs to the calipers. Basically, the 5 pressures are all identical when you step on the pedal (NON-abs assisted stop). Even if there are internal leaks between passages, the pressures will still be equal, and the pedal won't "sink", because no fluid is being displaced.

2019 F250 4x4 brake pedal goes to the floor so just a thought I pulled ABS fuse truck has brakes but i dony know
 
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