Hello everyone, long time lurker here, first time poster. Sorry for the long post, hoping someone can help save my Escape from the junkyard.

I have a 2008 FEH with 120k miles. About a week ago I got the dreaded regen brakes disabled and check brake system lights, braking was OK, but not 100% after the errors popped up. Now that I think of it, the brakes were feeling a slight amount weaker a couple days leading up to this. Limped the car home, opened the hood and could hear a high pitched whine (ABS solenoid stuck?) from the HCU area. Disconnected battery, lightly tapped the HCU and brakes returned to normal, no errors etc. HCU sounded normal when the key was turned to run.

I decided to do some preventative maintenance to prolong the life of the HCU and hopefully prevent the issue from coming back. Took the electric ABS motor out, inspected, cleaned, everything worked fine after this. Then I decided to change brake fluid, which is where I believe I made a made mistake. I undid the lower rubber line off master cylinder reservoir, let the fluid out and then topped back off. I then cycled the key to let the HCU build pressure and release (and purge any air?). Everything worked fine for a bit, HCU kicked on, brakes were strong. After a couple back and forth tests in the driveway the "check brake system" warning and red light came up and brake went to the floor. The HCU no longer kicks on and the check brake system light is on permanently, even after pulling the battery cable or resetting the ABS module in Forscan...

I then used Forscan, attempted to do an air bleed check and it fails, I assume due to air lock. So I bled each caliper manually, no air. Did a manual bleed with Forscan, no air but the ABS pump pushes out no fluid once it gets to that step, then the service procedure stops. As a last ditch effort I bled each line at the HCU, got a couple of tiny bubbles out of one port, but no change, HCU pump will not even attempt to turn when the key is turned. When I do a brake actuation test in Forscan the HCU actually sounds pretty normal for the 5 seconds it kicks on.

I'm pretty much out of ideas on what to do next. I still think there is air trapped in the pump, but that doesn't explain the pump not even attempting to cycle after the battery cable is pulled? Anyone experience this? I hate throwing parts at problems, especially since the only economical option is junkyard parts in this case and I'd have to reuse the old ABS module.

Thank you in advance for any advice.

 

I was able to solve this issue - wanted to share my procedure just in case anyone finds this useful. No scan tool or specialized tools are required to bleed the Ford Escape Hybrid brake system, even if it is full of air. This applies to 2005 - 2008 Ford Escape Hybrids with C1477, C1525 codes in the ABS module. If air gets into the system, the ABS pump/HCU stops running, which may be confused for a dead hydraulic control unit. The ABS pump kicks on when you turn the key to on and randomly during driving as the accumulator uses up pressure (the buzzing noise).

In order to bleed air out of the system you must use pressure - either by sucking at the calipers or pressurizing the brake fluid reservoir, or both. You can easily pressurize the master cylinder, follow the hose that is attached to the cap, hook up either an air compressor line (I clamped on a air blow nozzle) or hand pump and pressurize to 30 psi. I then used a cheap Harbor Freight hand pump brake bleeder to suck at the calipers. This worked great, a ton of air came out both front calipers that didn't want to come out with manual bleeding. After this the brake pump started to kick on after turning the key. I then cycled the system by turning the key to on, then off, wait 5 min, you will hear a hiss of fluid being let out of the accumulator into the reservoir. I did this about 15 times to let the pump/accumulator tank purge air. The ABS and check brake system warnings went out by themselves after this.

There is more information on the procedure at this link: Ford Escape Hybrid Brake Bleed Function - Snapon Diagnostics Product Forums

This procedure worked for me. I think there might still be a small amount of air in the accumulator as it takes a few seconds longer for the pump to turn off - but I think this air will slowly work itself out with time. This brake system is very sensitive and holds a lot of brake fluid, have 3-4 quarts on hand. I believe changing the fluid will do a lot to prolong the life of the HCU and keep therefore cars out of the junkyard. The brake fluid lines are right above the exhaust and the pump is right next to it too, so the fluid going to the HCU gets cooks over time and pretty dirty. There are also several rubber hoses around the HCU/master cylinder that can cause issues and make it seem like the HCU has gone bad, along with the flex hoses at each caliper. Hope this helps someone in the future.

 

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Really great. Thanks. My '10 doesn't have this system but this is great.