Hello everyone,

I've got a 2017 f-350 dually flatbed. I let the front brakes get really bad, and went to do them the other day. I've worked on cars for a while but i'm a heavy equipment mechanic by trade and don't know a ton about cars. Here's what i've done so far

1. replaced pads,rotors, calipers and mounts and both brakes hoses. Bleed the system
2. thought it was good and went to work the next day and made it about 2 miles until the brakes were smoking
3. took it all apart again and found one of the seals on one of the cailpers was torn/ damaged - presumably from the heat
4. replaced the new calipers with another set of new calipers. Bled the system
5. What i found is that once you depress the brake and release it, the caliper does not retract and keeps the brake locked up. This is the same on both sides
6. Tried all variations of bleeding to try and get any air out.

my thoughts are,

1. the ABS HCU - i think they call it, got some debris in there and is not allowing the fluid to go back towards the master cylinder, therefore not letting the brakes release. I had noticed a few weeks before this that when you're traveling maybe 30mph and slow down quickly for a stop sign or something, ill feel the abs for a very split second.
2. Is it possible an oring or seal in the master cylinder rolled over or something and isn't allowing the fliud to flow back?
3. Just for the sake of pulling at straws you think i could try and bleed the master cylinder?

Some one please be my knight in shinning armor! Thank you

 

You might look for the upsurge in the master cyl when releasing the brake pedal.
If you loosen one of the brake lines at the master cyl, after a brake application does it relieve any of the pressure?

Depending on the result you get there might help pin down if it is a master cyl problem or ABS problem.
What do you think?
As far as any knight in shinning armor, until we get better info just a guy riding a donkey lol !

Also, if there is any air trapped in the lines it will expand as it gets warmer and could be applying the brakes.

 

So i took off the lines on the master, and the calipers still did not release. I tried to depress the caliper piston while it was still mounted and it didn't seem to budge. While i had the lines off the master, i bled it and to no surprise, that didn't do anything. The only thing left is the HCU for the abs. Do you think i could by pass it as a test. Take one of the lines from a wheel and go directly to the line coming off that master, essentially bypassing the abs for that one wheel. And if after i press the pedal, and it releases, I could rule that the HCU is the problem.

 

If i replace the HCU, does it have to be programed from the dealer or someone with a scanner much more expensive than mine?

 

Before replacing the HCU, crack open the bleeder at the caliper to see if it releases.

 

If i crack the bleeder, i don't get a "squrt" of oil and a sudden relief of pressure. if i open the bleeder and compress the pad with a pry bar or something, oil will come out and will have loosened the pads from the rotor until i press the brake pedal again. This is happening on both sides.

 

If you didn't have this problem until you replaced some hydraulic parts, I would lean toward trapped air in the system.


A capable scan tool is required to open the solenoids in the ABS unit to allow that trapped air to exit..

 

I was afraid of that. Do you think if i used one of those Motive Power Bleeders at like 20 pounds, that would work?

 

The ideal thing would be to have a pressure bleeder and scan tool . That way you could keep constant pressure on the system and operate the solenoids at the same time.That is the better way to get the air out , but sometimes we need to to the best with what we have available.