2013 Lincoln MKX soft brake pedal

Anthony Mechanic Wisconsin Posted   Latest  
Resolved
Braking
2013 Lincoln MKX 3.7L (K) 6-spd (6F50) — 2LMDJ8JK7DBL44670
Brake Pedal Goes To The Floor

Good morning guys, I have a Lincoln here that would I would appreciate some help on. Customer complaint of soft brake pedal. Bled brakes out including command abs bleed, no changed. Clamped all brake hoses off to eliminate possible bad caliper, no change. Concluded bad master cylinder so changed it and power bled the brakes numerous times with no change. Where do I go from here? I've read a little on the possibility of sticking valve in HCU but how would I go about diagnosing that? Thanks!

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Rudy Technician
Utah
Rudy
   

Antney- The HCU is the problem 99% of the time on those vehicles. (Ive replaced at least a dozen or more) Do the ABS bleed again and this time pay attention to which solenoid sinks the pedal lowest and has the lowest return to the top. If they all drop and return equally, you may still have air, though unlikely.

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Helpful
Pat Technical Support Specialist
California
Pat
 

After clamping lines to isolate the calipers and having the same poor pedal feel, the next step would be plug off the master cylinder…crack the plugs to bleed any air out of it while someone is on the pedal, then see if things improve. The HCU is tough to “test”…so all we can really do is prove that the problem is not downstream of the hoses (which you've done)…leaving the problem to be either…

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Kevin Technician
Alberta
Kevin
 

Rudy is right on HCU. Had the same issue on a edge. Make sure the brake booster is perfect as there is TSB for that concern. They have a tendency to fail.

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John Owner/Technician
Ontario
John
 

hello I had the same issue on a Edge there is a service bulletin on the boosters giving out

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Kim Diagnostician
Missouri
Kim
 

Anthony, I agree with Pat and Rudy but before you condemn the HCU, go out and do a few hard ABS stops. I've had Fords that come in that have a low brake pedal after the customer performed an ABS stop. I take them out and after a few hard ABS stops, the pedal returns. I re-bleed them but I never get air. I suspect the HCU is sticking.

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Nelson Diagnostician
North Carolina
Nelson
 

Isolate and eliminate the M/C as being the source of the problem. The Thexton 803P Universal Master Cylinder Plug Kit is a nice kit I use for this type of situation

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Randy Curriculum Developer
North Carolina
Randy
   

Let's build on that thought. After isolating the master (if it's good) reconnect the lines and bleed. Then go to each outlet port of the HCU and disconnect the outlet for each channel, one at a time, and see if the low pedal continues. If plugging one channel creates a good pedal feel the problem in downstream in that circuit. If all of the isolated output circuits still present a low pedal the…

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Pat Owner/Technician
California
Pat
 

If clamping on hoses with linelocks causes damage to the hose, then the hoses should have been replaced 5 years ago.

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Randy Curriculum Developer
North Carolina
Randy
 

Agreed ;)

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Mark Engineer
Colorado
Mark
 

Randy Thanks for the reminder about not clamping off brake hoses. Here is a great article about “imploding brake hoses” when the inner liner is damaged techshopmag​.​com/imploded-brake…

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Tanner Instructor
South Carolina
Tanner
 

Randy brings up a valid point about blocking off lines from the HCU. To make this easier you can go into the abs module and turn on/off the outlet valves as well as the inlet valves for each wheel. If you pump the brakes up while doing this you will feel the pedal get hard when you close each valve and then the pedal will drop slightly when it is opened again. if The HCU is bad, normally…

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Louie Technician
New York
Louie
 

I had the same problem.I replaced both rear calipers and it went away Even though I clamped the brake hoses.

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Bruce Owner/Technician
Massachusetts
Bruce
 

Brake booster has a campaign. Warranty extended to 150k 0r 10 years whichever occurs first.

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Anthony Mechanic
Wisconsin
Anthony
   

I'm a little confused how a bad booster could make the brakes go all the way to the floor? Could somebody explain the concept? Everytime I've encountered a leaking booster it caused hard brakes not soft.

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Alan Owner/Technician
Mississippi
Alan
 

My thoughts exactly

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Bruce Owner/Technician
Massachusetts
Bruce
 

Happened to my 2012. Soft pedal with minimal braking when it fails completely.

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Kevin Technician
Alberta
Kevin
 

You want to eliminate brake booster as part of the brake foundation. In the case of the TSB you can sometime hear a vacuum leak inside, underneath the dash with or without pressing in the pedal. Having a defective brake booster would cause the pedal to sink way lower (almost to the floor) and then it would be rock solid without any braking power (you might get few 100psi maybe 500 if you take a…

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Steve Owner
Indiana
Steve
 

Find a gravel parking lot and force an abs stop. You can feel the abs cycling, if you can accomplish this, and may take more than once, you will get the air out

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Allen Owner/Technician
Texas
Allen
 

I do land rovers, wear the abs out on gravel; 50+mph full on stops; 3-5 stops, typically brings pedal back.

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Anthony Mechanic
Wisconsin
Anthony Resolution
 

I replaced the HCU with part from Ford and it corrected the condition. Thanks for the input and tips!

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