Brakes VERY soft despite bleeding and new MC

[captain chaos]

So I have a 2000 Expy 4wd, EB, 5.4 with some brake problems.

The pedal is very soft and will sink to the floor. I've replaced the MC, bench bled that, checked all calipers (no leaks there) and bled the brakes EXTENSIVELY. Still no dice, the pedal just WILL NOT firm up and no matter what will not hold (slowly sinks to floor). There are no leaks anywhere, it never loses any fluid but I just can't get any kind of pedal.
The PO has replaced the rear brake lines and possibly the MC. Is it possible they did a crappy job and pumped the ABS module full of air, which is now trapped in there?

 

[1955moose]

That's my guess. Check around the lines at Abs, real common that later ones leak. 03-07 years seem the most troublesome, but very possible yours is. A trick we used to do years back, was very carefully with lines attached, pull back master cylinder from booster, and see if wet at seal. If you bench bled master, and get clean bubble free fluid out all 4 bleeders, your problems elsewhere. Another thing that sometimes happens is the mechanic or owner puts the left caliper on right and right on left. With the bleeder on backwards, facing wrong direction traps air. I have same year same model Suv. I'll check mine later and report back.

Sent from my N9131 using Tapatalk

 

[captain chaos]

There's no signs of leakage anywhere.

Of course that begs the question as to how to get the air out of that accursed ABS module.
OR
is it possible the module is bad and has an internal leak or something.

 

[mrphixit]

When did the problem First show up? Was it fine and then you did work on it or did you do work on it and then the problem arose?

 

[mrphixit]

So I have a 2000 Expy 4wd, EB, 5.4 with some brake problems.

The pedal is very soft and will sink to the floor. I've replaced the MC, bench bled that, checked all calipers (no leaks there) and bled the brakes EXTENSIVELY. Still no dice, the pedal just WILL NOT firm up and no matter what will not hold (slowly sinks to floor). There are no leaks anywhere, it never loses any fluid but I just can't get any kind of pedal.
The PO has replaced the rear brake lines and possibly the MC. Is it possible they did a crappy job and pumped the ABS module full of air, which is now trapped in there?

I have had this problem with my 99 5.4 XLT after I bled the brakes. What I did after much googling was took it out onto a gravel road and slammed the brakes on at 10 mph, then at 20 mph , again at 30 mph, 40 mph , and finally at 50 mph the abs kicked in and started working. Up until then they would lock up and stay locked until I let up on the pedal. At 50 they locked, released, locked and released without having to release the pedal. I believe I remember reading that expensive fix was to take it to the dealer and have the ABS scanned or something for about $150. Cheap fix worked for me. I believe the problem I had was caused by me using a C clamp to push the caliper piston back into the caliper when installing new brake pads. Apparently this is not supposed to be done because it screws up the ABS. I still do it and have to go thru this gravel road process every time but my brakes start working right and the pedal stiffens up with no drift-down to the floor.

 

[TobyU]

I have had this problem with my 99 5.4 XLT after I bled the brakes. What I did after much googling was took it out onto a gravel road and slammed the brakes on at 10 mph, then at 20 mph , again at 30 mph, 40 mph , and finally at 50 mph the abs kicked in and started working. Up until then they would lock up and stay locked until I let up on the pedal. At 50 they locked, released, locked and released without having to release the pedal. I believe I remember reading that expensive fix was to take it to the dealer and have the ABS scanned or something for about $150. Cheap fix worked for me. I believe the problem I had was caused by me using a C clamp to push the caliper piston back into the caliper when installing new brake pads. Apparently this is not supposed to be done because it screws up the ABS. I still do it and have to go thru this gravel road process every time but my brakes start working right and the pedal stiffens up with no drift-down to the floor.

Did you open bleeder screw when you pushed piston in so fluid didn't go back through lines and into abs unit??
I would think this would minimize or eliminate your issue when doing pads.

 

[mrphixit]

Did you open bleeder screw when you pushed piston in so fluid didn't go back through lines and into abs unit??
I would think this would minimize or eliminate your issue when doing pads.

It probably would. The gravel road track works every time so I don’t worry about it too much. I was just replying to the original post to let him know that this trip might work for him too seeing as nothing else seems to have worked. Thanks

 

[captain chaos]

After reading about a number of Expys/f150's with the exact same symptoms being caused by the abs pump itself, I removed the pump from the truck and just ran new hard lines to bypass it completely.
I now have no abs but I really don't care about that anyway. The brakes feel great so I'm happy. I was concerned that the bias would be screwed up and the rear would lock easily but testing has proved that's not the case. Brake bias seems good without the abs pump in the system.

 

[WWhite]

I had a soft pedal after doing a front brake job on my 99 Eddie Bauer. I used the Forscan software to bleed out the ABS module and the pedal is nice and firm.

 

[TobyU]

I had a soft pedal after doing a front brake job on my 99 Eddie Bauer. I used the Forscan software to bleed out the ABS module and the pedal is nice and firm.

I've done brakes many times on ford trucks including 90, 92, 95, 97, 2000, 2001, 2003...this has been pads and rotors, caliper rebuild kits, new caliper, and several brake line replacements.
I have NEVER had to use a scantool or any other method other than bleeding brakes by having someone pump them as I instruct them "down", "up" as I open and close bleeder screws.
You also need to leave the screw closed after a few bleeds and have them pump 4-5 times to build pressure then bleed some more.

It can seem like it takes forever to get the air out but it will work on older ones without any other special equipment or procedures.
Sometimes you esp on a rear line replacement, you may pump almost a whole master cyl full worth of fluid until you get the air out and that line and wheel good and solid.
You HAVE to keep the fluid level in the master cyl and not let it get low or you push air back in from the front and mess it all up again.

It's not rocket science but tedious and a little time consuming.
I have seen a rear line take 25-30 pumps easily to get all the air out.

You can get it all hooked up but leave the line at the end at caliper or wheel cyl unhooked and fill master cyl and let it "gravity" bleed a little for 20-30 mins as you do something else and this will speed up your actual bleeding pumping time.
I will not use the vacuum bleeders or one man blenders etc.

Never had a problem the old way and too many prettier people have issues doing different ways so something is up.