December 05, 2021, 11:23:25 AM
collapse

Author Topic:  I believe I have a bad ABS unit, anyone heard of this?  (Read 320 times)

Offline LMKS012

  • Jr. Member
  • *
  • Thank You
  • -Given: 0
  • -Received: 0
  • Posts: 11
  • Ecobooster
  • Liked:
  • Likes Given: 0
I believe I have a bad ABS unit, anyone heard of this?
« on: November 12, 2021, 09:10:12 PM »
Hey guys, well before I did the full 2013+ brake upgrade, I had a problem were the passenger side back caliper would actuate much more than the drivers side back caliper and would end up wearing out.

This happened once and I figured the wife just drove with the parking brake semi-engaged or somesuch, so I just changed the pads, made sure everything was bled and everything seemed to work fine.

Almost a year later I have the same issue, the passenger side rear pads are gone (eating the rotor this time) and the drivers side rear is got virtually no wear.

So, I take it as a sign of a bad caliper and just decide to take the plunge and put in an updated version, the complete 2013+ brake system.  I installed the brake booster, master cylinder, all new hoses at each corner, all new splash shields, new calipers, new pads, new rotors.  I even upgraded to DOT4LV fluid and found I couldn't totally bleed the system, since after 12 liters of brake fluid I STILL had a spongy pedal.  The brakes actuated within 1/2" of pedal throw, but the pedal doesn't get firm until way down.

I was sick and tired of spending money on brake fluid, so I used a 20ft 4mm internal diameter silicone hose along with a 7mm clamp to connect to each bleeder screw.  I also wrapped the bleeder screws in teflon tape to prevent leaks when bleeding.  I ran through the bleed procedure with a Foxwell NT630 scan tool as well as a laptop setup with Forscan and a vLinker cable.

Now, after doing that for 2 hours (which is 300 pedal presses after doing bleeding for a total of 8-9 hours over 4 other attempts for well over 1200 pedal presses) I said screw it and put it all back together and took the car out and drove it.  After about a half hour I pull back in the driveway (brakes were fine the whole time, regardless of the spongy pedal) and check the heat of each rotor.

The front two were damn near identical and the rear passenger was almost the same as both fronts.  The rear drivers was no-where near the others, like less than half the heat temp.

So, at least I have identified that the rear drivers caliper circuit is the problem.

I jack up that corner, pull the wheel, and run the hose form the caliper to the reservoir again, and proceed to do the service bleed with both the Foxwell and the Forscan methods.

One thing I notice when doing the Foxwell is that if I go in I notice they allow you to actuate solenoids on/off and everything else, but the actualy controls for the left rear (drivers side rear) are MISSING from the scantool.  It had the left front, right front, right rear and that is it, no left rear menu options.  I have an email into Foxwell at this point to find out what is going on with their tool.  I also notice that Forscan can only do the service bleed procedure and does NOT have the ability to actuate each circuit independently, which is a real disappointment.

Now, the only thing I can surmise is that the left rear (drivers side rear) circuit in the ABS unit has a stick valve that is restricting fluid flow to that caliper, as well as not being able to fully bleed that caliper because of said "stuck valve".

That would explain why the original brakes had the other side eat the pads.  It also explains the soft pedal and the inability to get air out of the entire system.

So, I guess I am on a search for a replacement ABS unit.  I have to see if I can reprogram it via Forscan, or if I need to take it to a Ford dealer to use their IDS system.

If Forscan will reprogram it, then I can get an inexpensive take-off salvage unit and see if that works.  If a dealership is going to charge me to program, I might as well buy a brand new ABS unit and have them do the replacement and reprogramming as well as another bleed session.

I just have never heard of an ABS unit failing like this, but I can't see any other sort of explanation for what I have been dealing with.  Frustrating is a MAJOR understatement at this point.

If anyone has any input on this, I would be very grateful to hear it.

Offline SHOdded

  • Forum Supporters
  • Elite Member
  • *
  • Beltsville, MD
  • Thank You
  • -Given: 13059
  • -Received: 4249
  • Posts: 15963
  • Liked:
  • Likes Given: 69
Re: I believe I have a bad ABS unit, anyone heard of this?
« Reply #1 on: November 17, 2021, 07:33:26 PM »
Quite a story.  Have not heard of an ABS unit failing on the SHO.  Definitely the odd master cylinder here and there, maybe a booster or two ...

We are seeing a rash of failures tho on the Edge platform, primarily for gen 1.5 - 2011-2014, where fluid has not been regularly flushed.  Basically a loss of assist but no whistling or squeaking that is characteristic of booster failure.  The master cylinder has never been at fault.  And of course, NO codes from the ABS system except for lucky ones that get an HCU related valve stuck code.

Looking forward to input from fellow forum members.
2007 Ford Edge SEL, Powerstop F/R Brake Kit, TXT LED 6000K Lo & Hi Beams, W16W LED Reverse Bulbs, 3BSpec 2.5w Map Lights, 5W Cree rear dome lights, 5W Cree cargo light, DTBL LED Taillights

If tuned:  Take note of the strategy code as you return to stock (including 3 bar MAP to 2 bar MAP) -> take car in & get it serviced -> check strategy code when you get car back -> have tuner update your tune if the strategy code has changed -> reload tune -> ENJOY!

Offline LMKS012

  • Jr. Member
  • *
  • Thank You
  • -Given: 0
  • -Received: 0
  • Posts: 11
  • Ecobooster
  • Liked:
  • Likes Given: 0
Re: I believe I have a bad ABS unit, anyone heard of this?
« Reply #2 on: November 21, 2021, 09:46:48 AM »
I might as well post a follow-up...

Well, I finally got in a replacement ABS unit, a take-out that had the exact same part number on it as the one it is replacing.  I removed the 4 screws and took the electronics off the back, took off my ABS unit, disassembled it the same and used my electronics on the replacement valve body.

I then used a syringe and master-cylinder bench-bleed hoses and flushed the old fluid from the replacement ABS valve body. I did that about 2 times to make sure good fluid was in the replacement valve body.

I installed it in the car, left the lines to the calipers loose so that it would "gravity bleed" a little... Once I got fluid coming up the threads I tightened them all down.

I then proceeded to jack the car back in the air, put it on jack stands, pulled the wheels and did a pressure bleed followed by an ABS bleed.  I went through another 5liters of DOT 4 LV brake fluid, but I wanted to be sure the ABS unit was fully flushed all the way to the calipers.  I got large and small air bubbles out of all the calipers during BOTH sets of bleed procedures.

Got it all done and the brake pedal didn't feel much different with the car started.

Took it for a drive and I can say the brakes work extremely well.  They start grabbing within 1/2" to 1" of pedal travel and when they are jammed to where they finally get "stiff" they actuate ABS on dry pavement.  So they work, just have a much "softer" pedal feel compared to what I am experiencing with my 2017 MKT Town Car.  I am wondering if the Town Car doesn't have a different brake booster, since that car is all about "ease of driving" for extended periods vs "driver feedback".  What I mean is the steering on the Town Car is super-light, the brake pedal is super-firm and in general it feels almost like driving a simulator more than any other car I have ever owned and it is quite a bit more stiff suspension-wise.  My MKS in comparison has a very heavy steering feel, soft brake pedal feel and very "floaty" and "soft" suspension-wise.  I mean the Town Car feels like you are driving a much lighter vehicle where the MKS feels solid and heavy.

Anyways, I took it for a drive, came back and used a IR gun to measure rotor temps...

Left Front (Driver) - 144.8F
Right Front (Pass) - 147.1F
Right Rear (Pass) - 214.9F
Left Rear (Driver) - 121.7F

So, the fronts temps are equal and the left rear is about what you would expect a rear caliper to be compared to the fronts, but the right rear is WAY over what I would expect.

Today I will pull that wheel, pull the caliper, retract the piston in and see if I feel any sort of binding or other piston issue (might be a stuck parking brake ratcheting mechanism, or a bad piston seal that is jammed) and then pull the pads and double check that they move freely in the slides (they are all new so they should) and if not figure out why they are binding.

If I can get that caliper working properly and the temps after driving are about the same as the drivers side I think I will be happy overall.

As long as the brakes work well I guess I will have to just get used to the softer pedal feel.  I do know there is a different pedal bracket used in 2013+ cars compared to 2012 and under.  Just no idea if they changed the leverage point for the brake rod or if they changed the rest of the geometry to allow less pressure (which would increase pedal feel, but considering the over-built nature of the 2013+ brake system that might now be such a bad thing).

All I know is that I have replaced everything but the hard lines themselves, I get plenty of fluid out of the calipers when bleeding and in general feel that there is not much else I can do.  As stated the brakes work great, so I can only hope it is just getting used to a softer "feel" than what I was expecting.

I mean the only other thing to consider would be a bad brake booster that is "overboosting" when used.  I personally have never heard of that.

Offline Macgyver

  • Super Moderator
  • Elite Member
  • *
  • *
  • Eastern Pa.......
  • Thank You
  • -Given: 100
  • -Received: 391
  • Posts: 1019
  • 2020 Red ST
  • Liked:
  • Likes Given: 30
Re: I believe I have a bad ABS unit, anyone heard of this?
« Reply #3 on: November 21, 2021, 11:14:27 AM »
It is hard to diagnose online. It seems you have a handle of what may be happening.

Keep us posted on what happens with the rear brake repair.

Offline LMKS012

  • Jr. Member
  • *
  • Thank You
  • -Given: 0
  • -Received: 0
  • Posts: 11
  • Ecobooster
  • Liked:
  • Likes Given: 0
Re: I believe I have a bad ABS unit, anyone heard of this?
« Reply #4 on: November 28, 2021, 03:19:37 PM »
Well, I pulled everything apart on the passenger side rear caliper.  The pads slide freely, no binding.  The parking brake engages, applies pressure to the pads.  When the parking brake is disengaged there is no more pressure on the pads, so no drag.

I still pulled the caliper up, rotated the piston in, it goes in freely, as in no binding, catching, nothing that would indicate a binding issue.

I then put it all back together, applied the brakes a few times, same pedal feel, then while holding the brakes applied the parking brake, again it released and no drag.

Went for a drive, it was fine, all the brake rotors were in the correct temperature range, about 148f-150f front, about 123-127f rear.

I then applied the parking brake, went in for the evening...

The next day I drove it around, came back and again the rear passenger side was way hotter than the drivers side rear.

Took it all apart again, this time I turns the caliper in a few extra turns after bottoming out.  I also tried turning it the other way and it would not rotate counter-clockwise.  So that just means that it operates as it should with the emergency brake allowing the piston to move outwards and the self-adjuster able to rotate freely in the direction of piston movement outwards.

I also took the opportunity to disconnect the parking brake cable from the caliper and pull the cable by hand out as far as it would go and verify that the return spring does pull it back into the sheath properly.  It all works as it should.  I even took the opportunity to spray some cable lube on the coated cable while it was pulled out MUCH further that it ever does in use.

Put it all back together and again, verified that the pads grab when under pedal pressure and when the emergency brake is applied and that there is play in the caliper when the emergency brake is disengaged so there is no drag on the rear caliper.  Everything passed with flying colors.

I will drive it a few days without using the emergency brake and see if there is any "change" to how everything operates and if there is any increased rotor temps.  I am expecting there not to be.

I did also pull apart one of the old calipers and the entire e-brake assembly is bathed in brake fluid and I can see why it is hard to bleed air out of them, so I will be removing both rear calipers from their brackets and holding them sideways while pressure bleeding to see if that doesn't "fix" the pedal issue.

 


SimplePortal 2.3.5 © 2008-2012, SimplePortal