Brake Problem
 

Could u please explain the fast apply hold and the slow apply leak down on the M/C. I'm assuming my old ABS unit was good so I think I'm gonna put it back on with the new M/C and try that. Thank God the junk yard said I could return the ABS unit for a refund within 30 days.
THX.
Glenn

I personally have more confidence with a Ford/Motorcraft M/C then the national chain auto parts stores.

The only way to bleed an ABS controller is in the vehicle with the right scanners. But again, it's rare for the ABS controllers to go bad.

At our facility we stopped bench bleeding M/Cs. We would install the M/C with the rear of the vehicle up on a lift so air would head to the back of the M/C where the compensating ports in the M/C are located. With the brake lines in the ports but the line nuts not installed, we would put rags under the M/C then add fluid. As the fluid came out of the ports we would then tighten down the line nuts. With the rear of the vehicle still elevated higher then the front we would lightly tap on the M/C with a hammer to try to dislodge any air bubbles from the bores. We would then partially stroke the pedal and crack each brake line nut until we did not see air bubbling out. After this we would proceed with a normal bleed.

I had just looked at the link above and it was not working so I reset it. I also put the page in my Facebook page noted below. It came from a Ford service manual and the fast apply reference is noted in there.

The master cylinder cups seal with their lips against the M/C bore, and the more pressure they are holding, the tighter they are against the bore. So in theory a fast apply with hard pressure will seal the cups, whereas a light pressure apply like at a stoplight can allow fluid to go past the cups. That mostly works, but if the cut is too torn buy some corrosion, or the cups are rolling their edges, it may hold hold true. But it is a good general rule.

In another forum a few months ago there was a truck owner with rear drum brakes. He kept developing air in the system and could not figure out where it was coming from, even replacing the rear wheel cylinder twice from the same national auto parts house. He finally got Motorcraft wheel cylinders and the problem was solved. The issue was that this vehicle did not have what is called a residual pressure valve in the M/C like older design vehicles had, and the wheel cylinders that were being sold for the truck from the national parts chain were copied from an older design.

Now there is nothing about the parts in this story that is going to help you, but what is happening in the aftermarket is a lot of parts are being made all over the world and the suppliers are not paying attention to the little details. A wheel cylinder is a wheel cylinder and a master cylinder piston pack is a master cylinder piston pack. We are seeing more and more that even experienced mechanics are chasing their tails trying to find what's next on the list when the original problem is still the problem, even when there is a new part in the system.

I really hope all you have is a M/C problem. But while you getting to the ABS controller you should try the paper clip check.

Just Call Me Brake Dummy
 

Hey Thanks a million Jack for your info and trouble. Ford dealer in 3 counties did not have a M/C so I order a Wagner to get it here before Monday got to have it workn by then. I pulled the valves out of my ABS HCU and attempted to see if anything was stuch but could not get to the other valves, I will try that paper clip test, I did pull of those accumulating valve covers and did see alittle fluid in one of them when I was cleaning it. I gonna put it back on the truck with the M/C and carry the junkyard one back for a 100 refund. I will try bleeding the new M/C as you just described and see what happens. I can put the truck on jackstands to kick off the ABS and will try that two. Thank you so much for your help, I pray God blesses you for all yor help with everyones problem. I've done mechanic work for yrs even have all kinds of certificates with GM, but this dog here has me bit. Thx again Jack and I will let you no how it goes.:-wink

I'd order in a Ford M/C.

hey jack,
Took ur advice when I got to Advance the M/C was made in China, refused and went to Ford for one $180, bled it put it on jack up truck ran then bled it drove down dirt rd over 40mph hit the brake no wheel slide went back to shop bled and again then repeated it all again now when I stop the truck the pedal start to fade to floor but stops about half way to the floor now instead of stoppin 11/2" of the floor but it still will creep off if I dont pump it quick and hold pressure on pedal. What do I do now, no ABS light came on at all, even when I ran it on the jack stands.

Since it's not near the floor now it means that it's not bypassing within the M/C, but air within the system will do what you describe. Without an IDS it's just going to be a bear to bleed.

Using an assistant to push the pedal, first go back though and bleed off a little at each line nut you disturbed - if no bubbles move to the next. Tap lightly whatever you are bleeding with a small hammer or 1/2" ratchet trying to shake loose any bubbles.

Bled at all four corners insuring no air. Repeat dirt road 35 mph series of stops to try to get the ABS to activate then re-bleed at the four corners, seeing if air has come out. We might have ended up doing this of 4 to 8 hours on problem vehicles without the scanner.

You mentioned tearing apart an ABS controller. Is that the one that is back in the vehicle now? Is the ABS going through it's normal indications on start-up?

Bad Brake
 

Hey jack,
Yes its mine the one I put back in the truck. It seems to be system cks on startup and then goes out and it didn't Light back up on the test drive down the dirt rd, nor especially on the jack stands. I ran it up to about 50mph on the stands and just applied the brakes like I would have on a normal stop, and no ABS light, but I did get more air especially out of the back corners. I did notice I was gettn about 1/3 of the amount of fluid out of the front bleeders versus the back ones. I bled it both ways today, pump and hold down method, and crack bleeder and push down and hold pedal and I would close the bleeder before it reached the bottom. I got more fluid with the single stroke on all 4 corners versus the pump and hold. It baffled me about the small amount of fluid from the front calipers.
I will do what u said 2morrow, can i buy one of the scanners your talkn about, or is it a ford only tool?:-jammin

I don't think you want the expense of an IDS.

I'm concerned about what the ABS is doing too. Front flow should not be an issue.

Bad Brake
 

jack,
do u mean the amount of flow on the front bleeders is normal, shouldnt I be gettn more fluid from the front than the back. I went down the dirt road several X's yesterday came back and bled more air out. Drive the truck all around today at work was very cauious thou. The pedal still holds about 2" off the floor. I order a Power Bleeder to try what do u no about them, its a forced fluid bleed. Looks like I might have to break down and buy a new ABS unit $1400. When I went down the dirt road yesterday speed over 40mph hit the brakes and no slide from wheels I feel like it performed ok. I tried the same test on a gravel road and got a little slide on it. Whats your word?

Thx,
Glenn

You really, seriously, need to bleed the brakes with the ABS unit being exercised. That means the right diagnostic tool.

I've been-there-done-that with the Kelsey-Hayes ABS unit. There is NO WAY to get all the air out of it without the proper bleeding procedure. I went through the same thing you've been doing on a Chevy Suburban which is the SAME SYSTEM as our Superduties.

Low pedal, kept bleeding, kept bleeding, getting a little bit of air each time.

Finally, my brother-in-law took my advice, got it professionally bled at a Chevy dealer, and it's been GREAT ever since.

Find a mechanic who knows what you're talking about and is willing to deal with you.

Glenn,

I'm worried that something in the ABS got messed up when you took the unit apart. Honestly, I know of no mechanic in the brake industry (manufacturer, testing, etc) that would disassemble a unit without training and the manual. Everything has to be perfect.

The long pedal from this side of the computer appears to be air, and as Kaewat stated and I earlier referred to, having the electronics is the best way to bleed. It can be done the "dirt road" way, but it is not easy. In our facility no one would not use the scanner to do the job if it was available. And if the ABS controller is not firing all the circuits, you will never be able get the air out of that circuit, dirt road or scanner.

Even with air in the front brake chambers, the ABS controller should be firing off those wheels, but you're not getting any reaction. You're throwing a lot of time and money into this and it might be time for getting the unit checked and bled with a scanner. A pressure bleeder will not do anything that a manual bleed would do. In fact, you can generate much higher hydraulic pressures when manually bleeding then with a pressure bleeder. But before taking it to the dealer it may be prudent to make sure the connector pins are OK and fully seated. Although a failure of that type should set off the ABS light full time.

Brake Bad
 

Hey Jack I'll take that under advisement and see if I can get it checked thanks for all your help.:)

Hi all, sorry to hijack and reopen, but I am in the middle of this exact issue. Hope Jack (fmtrvt) chimes in.
Truck was hit left front corner, bumper wrapped around abs, but doesn't look like it hit it. Immediatly after impact, when I came to a stop, pedal went soft. Body work done, master cyl diagnosed as bad, replaced (new aftermarket) bled, no change. Shop didn't charge me for mc. Next day I buy a Motorcraft mc, bled very well, no change. Bench bled mc. I worked on Honda's for 20 years, dealership level, comfortable saying I did this part right. Truck stops, but really crappy pedal feel. Like a bypass.
Just did abs/paperclip test. One port almost pushed clip out. My manual says bad. Ft Collins Ford says they sold one abs hyd unit in 5 years.
I will let them diagnose (and charge me) tomorrow to be sure, but sound like abs?? Then I guess they will have to replace due to the scanner issue.
Sound like I am on right (but expensive) path here?
Thanks.

One more question please.
Will AE perform this procedure?
I don't have one, yet.

Thanks again.

Tom,

Unfortunately for both of us, AE does not do ABS.

It's rare of the ABS controller to need to be replaced, but NOT unheard of.