Has any one had to replace the Hydraulic Control Unit?

I am looking at the ABS inlet valve or dump valve as the cause of my brake dragging issues. I have replaced every thing else that I can think of.

The issue is that the brakes drag with in 10 miles of driving. Its not consistent and it not always the same wheel. Some times there are no issues and other times it just about locks up.

Since the stealer wants $600 would any one trust a junkyard HCU?


Here is what I have done.
Caliper pins
Calipers
Master cylinder
Hydroboost
Pads and Rotors
Hoses
Fluid

Anything else I have missed?

 

Ditch the ceramic pads I bet you put on there.

 

When you say it may not always be the same wheel, are you referring to that only one rear wheel can be dragging when this occurs? The ABS system is 3 channel. Meaning the front 2 are independently operating and both rear work together. If you have only one rear dragging, then it would not be HCU related.

 

It changes between the front wheels and rear wheels. Today it is the right front and rear.

 

Well did you put ceramic pads on it?

 

Oh boy, I can talk on this one!
Yes, I have replaced an ABS hyd control unit. They rarely fail, mine was bypassing internally after a hard hit on the left front. Soft pedal exactly like a master cyl bypassing. Part from Horizon was over 800, dealer had to install due to bleed procedure requiring special tool. I would not trust a used one. I also agree that it isn't the control unit.
Possible fluid contamination? Or pads.

 

what is wrong with ceramic pads?
i get 3-4 times the life out of ceramics as i do with semi metallic pads.
and the rotors last forever too..
i currently have 80,000 miles on the pads on my 02 diesel, and they are still over 50% use left.

 

well as per Ford's service guide this is what they state:

<table rules="groups" border="1" cellpadding="3" cellspacing="0" width="90%"><tbody><tr valign="top"> <td>

• Brakes drag

</td> <td>

• Parking brake component.

</td> <td>

• REPAIR or INSTALL new components as necessary. REFER to Parking Brake in this section.

</td></tr> <tr valign="top"> <td> </td> <td>

• Brake caliper guide pins.

</td> <td>

• REPAIR or INSTALL new caliper guide pins, seals and boots. REFER to Brake Caliper Guide Pins in this section.

</td></tr> <tr valign="top"> <td> </td> <td>

• Disc brake caliper.

</td> <td>

• REPAIR or INSTALL new brake calipers as necessary. REFER to Section 206-03 for front disc brakes or Section 206-04 for rear disc brakes.

</td></tr> <tr valign="top"> <td> </td> <td>

• Brake booster.

</td> <td>

• CARRY OUT the Brake Booster Component Test in this section.

</td></tr> <tr valign="top"> <td> </td> <td>

• Brake master cylinder.

</td> <td>

• CARRY OUT the Brake Master Cylinder Component Test in this section.

</td></tr></tbody></table>

these are the appropriated tests:

Brake Booster

1. With the transmission in NEUTRAL and the engine stopped, apply the brakes several times to exhaust the vacuum in the vacuum boost system or the pressure in the Hydro-Boost® system.

1. Hold the brake pedal in the applied position.

1. Start the engine.

1. If the power brake system is functioning correctly, the brake pedal can be felt to move downward after the engine starts.

1. With a vacuum type power brake booster, if engine vacuum is available to the power brake booster and no power assist is felt, replace the power brake booster and retest the system.

If power steering pump pressure is available to the Hydro-Boost® power brake booster and no power assist is felt, replace the Hydro-Boost® power brake booster and retest the system.
If power steering pump pressure is not available at the Hydro-Boost® power brake booster, check the power steering pump pressure and flow. For additional information, refer to Section 211-00.
On a Hydro-Max booster system, if power is available at the electric pump and no power assist is felt, replace the Hydro-Max booster assembly and retest the system.
If power is not available at the electric pump, correct the electrical concern and retest the system.
Accumulator, Hydro-Boost® Only

1. Start and run the engine.

1. Stop the engine.

1. Apply the brakes. The accumulator in the Hydro-Boost®power brake booster should retain enough pressure for at least two power assisted brake operations. If no power assist is felt, replace the Hydro-Boost® power brake booster and retest the system.

Check Valve — Vacuum Booster Only
The function of the power brake booster check valve is to allow manifold vacuum to enter the power brake booster and prevent the escape of vacuum in case manifold vacuum is lost during sustained full throttle operation.
To test the function of the power brake booster check valve:

• Start and run the engine for at least 10 seconds.
• Operate the brake pedal to check for power assist.
• Disconnect the vacuum booster hose from the power brake booster. Do not remove the power brake booster check valve from the power brake booster.
• There should be enough vacuum retained in the power brake booster for at least one more power-assisted brake operation.
• Replace the power brake booster check valve if it fails the above test.

Brake Master Cylinder

1. Disconnect the brake lines at the brake master cylinder.

1. Plug the outlet ports of the brake master cylinder.

1. Apply the brakes. If brake pedal height cannot be maintained, the brake master cylinder has an internal leak and must be replaced.

Compensator Port Check
The purpose of the compensator ports in the brake master cylinder is to supply any additional brake fluid required by the system due to brake pad wear and to allow brake fluid returning from the brake lines to the brake master cylinder to enter the brake master cylinder reservoir.
The returning brake fluid will cause a slight turbulence in the brake master cylinder reservoir. Turbulence seen in the brake master cylinder reservoir upon release of the brake pedal is normal and shows that the compensating ports are not plugged.

 

from my understanding they get the rotors hotter and if your towing a lot or hauling theyll warp your rotors real quick, thats what i was told but im sure if im wrong ill be corrected.

 

well as far as Chevy, I have used both. When I used ceramic they don't last nearly as long and always leave a glaze on my rotors. I normally use severe duty wagners which are a semi metallic..., they last the longest by far especially with all the miles and extreme weight I carry (mobile mechanic roughly 20k per yr and always fully loaded with tools, parts, and equipment -only a 1 seater anymore -lol)

 

the only difference i have noticed is that with ceramic pads the braking is much better,
they last 3-4 times linger, and no cleaning the brake dust off the wheels every week.
i have the ceramic pads on everything now.
the 88 superduty 4X4 conversion used to only get 15-20k out of a set of pads. since putting the ceramics on it i was getting 40-50k out of the pads.
and that was usually rolling between 25 and 30 thousand lbs.
since it has been retired to snow plow and backup truck status, i have close to 75,000 miles on the pads and they are still good. and it will face plant you into the windshield if you lock them up and are not wearing the seat belt.

 

I had the same problem the op is having. I warped all 4 rotors twice and replaced my lines calibers and everything else, the problem? The pads were ceramic pads. After ditching the pads no problems in 2 years. These trucks hate ceramic pads. If youre having luck with them... Good for you... Convince this guy he has to spend a lot of money just to have the same problem in the end.... I bet he'll even thank you....



But hey! What do I know

 

If its happening within 10 miles, the brakes have not really had a chance to heat up unless they are dragging from the get go.

How long ago did u replace the master cylinder relative to everything else? Next question is how full is master cylinder? I doubt it is but should it happen to be overfull it will cause your issue.

 

I had to go to the stealer today to get an alignment and had them look at the brakes since I was there. The tech wasn't able to figure out what it could be and just recommended to change calipers again.

I don't think that the caliper are the issue so I picked up a master cylinder from Napa and see what that well do.

 

I would have to agree there, doesn't sound logical that calipers would be the issue here and to replace them again....

I hope the issue does lie with that master, because I am scratching my head on this one. Good luck there buddy!