Hi Everyone!

So, I'm new here as my Excursion is somewhat new to me as well. I'm a lifelong car enthusiast, I have classic cars and motorcycles that I enjoy (usually) working on.. haha. Right now, I have been trying to track down a crazy brake issue that I have done a LOT of searching on this forum for answers. So far, I have come up short. Here is a summary of where I'm at. I'm hopeful that this will become a helpful post for this issue in the future.

The problem: Mostly when WARM, the truck will dive LEFT on braking. Enough where I do not want my fiance (or anyone else) to drive this vehicle I think she could lose control of it.

Over the winter, I replaced all of my front suspension, wheel bearings, hubs, everything.. you name it, it's new. I also replaced all 4 calipers and rotors, and pads. In addition, I have new tires and my truck has been aligned by my mechanic who I trust very much and knows these big trucks very well (they have other customers with Excursions) several times in hunting the problem down. In trying to pinpoint the issue, my mechanic has re-bled the brakes many times since they have replaced all 4 brake hoses, and also there is a flex line along the firewall that most folks don't know about that's been replaced. I guess it runs from the master to then split off to the rest of the hard lines.

We have replaced the front calipers again - front pads again - rotors again - all 4 corners. No change. So, the items I installed were deemed A-OK. I used PowerStop rotors and calipers BTW. SO, here we are.. uanble to find the issue. I gave the go-ahead this morning to replace the master cylinder. There have been discussions of bypassing the ABS module as well but I would really rather not do that. I also randomly read about adjusting the brake pedal or something in regard to pressure being applied to the master but I didn't really understand what that was all about, it seemed to be related to all 4 brakes locking up on someone's truck.

Any thoughts you folks have would be greatly appreciated. I am unfortunately far beyond lubing the slides, checking temps of rotors (all been done).. SOMETHING is making the pressure not equal in the system.. but for the life of me.. I cannot figure this out. Help!

Thank you!!

Jim

 

Did you replace the jounce hoses to the calipers?

Try swapping the front tires side to side.

Try swapping the front/rear calipers side to side. Front first, then rear.

Have you done a full fluid flush in the system?

 

For anyone with an Excursion, you best be replacing the factory brake lines/hoses. Just one collapsed hose has the potential to kill you.

 

Hey man - Yeah, all of those have been done. All 4 hoses are replaced with new. Also, the calipers while not swapped side to side, have been swapped completely with other ones.

 

See what the master cylinder does and go from there. I have a feeling that may fix it. There are a few more things to check if that doesn't, but lets hope it does.

 

With two circuits out of the master cylinder, if there is an M/C issue with these trucks, it will be either front or rear brakes or front/rear axle, if you will. The ABS controller breaks this into 3 individual channels: the rear brakes and the front brakes individually. You've already been flipping parts, so one would expect a part issue to have gone away.

Most of the friction materials that come with this class of truck are semi-metallic. Personally, I'm not a fan of "ceramic" fiber-reinforced friction in this class. With semi-mets, they develop higher friction as they get warmer, so for me, I always like to fingerprint brake temps during a pull. You've mentioned you did that, but no documentation of the results so meaningless for me. Sometimes pulls come from the rear brakes, and unless you know the "feel", it can be mistaken for a front brake pull. But, again, that would require the temp data.

The ABS controller on the 2001 Excursion can have a spool valve issue, bleeding into the accumulator. With the earlier ABS controlled, that can be checked. If the pressure to the right front is bleeding off, it will pull left. While it talks of travel, it can also cause a pull issue.

One thing not mentioned, have you flipped tires left side to right side?

 

Very helpful - YES, I'm sorry I forgot to mention, the tires have been flipped side to side. I'll let you all know what happens with the MC. After that I guess it could be the booster, but I doubt it. That's a real long shot.

This chart / diagnostic is helpful. I love this forum thanks guys!

Jim

 

I would check the ABS next if the MC doesn't fix it. Pay attention to what Jack posted above. He knows his stuff,

 

Welcome to the EX forum!

If you replaced the 4 flex hoses at the calipers you missed an important one, the flex hose from the frame to the rear axle. I doubt that it would be the source of your current issue but that hose is just as important as the four corner ones.

 

OK I'll make sure they change that one too.. I hadn't thought of that! Obviously.

 

I called them up and told them to change it out. Funny thing, I remember seeing it when I was working underneath the truck and yet it never occurred to me that it should be changed.

Fantastic suggestion thanks man.

 

The M/C and booster are not going to do anything for a wheel pull.

You can also try pulling the fuses for the ABS to see if there is an issue there. You will lose your speed signal, but your testing.

 

Is the ABS system a common issue with these trucks? I will certainly try pulling the fuse option to test it after they redo the master cylinder. Respectfully, I do think the master cylinder could be part of the problem, but the booster I agree I don’t think there really is any way that that would cause a pull.

QUOTE=TooManyToys.;19863305]The M/C and booster are not going to do anything for a wheel pull.

You can also try pulling the fuses for the ABS to see if there is an issue there. You will lose your speed signal, but your testing.[/QUOTE]

 

I originally had an issue with a sudden pull to the left in my 01 6.8 rwd with firm pedal application and discovered the LR running hot. After servicing the caliper slides it improved but still pulled left some, wasnt too bad so let it go. Like you I had replaced the ball joints, tie rods, center link on the front. One day had to panic stop and it darted hard left again. I believe it crept up on me slowly getting worse over a long time so I didnt realize it was that bad. After reading up on the forum had the wife move the steering back and forth with engine off while I was underneath and the pittman arm wasnt moving despite her saying she was "sawing it back and forth". Long short I replaced the steering gear with a Blue Top and it tracks dead center when braking. Even hard braking. Just a thought.

 

Last year I had an issue with my truck pulling right under braking. After going over my symptoms with my mechanic, he nailed the issue immediately. I had a tiny amount of rust building up under my left front ABS sensor. He removed the bolt holding the sensor into the knuckle and cleaned up the area around the hole where the sensor mounts with a file and abrasive disc. With a small amount of rust building under the sensor, it changes the relationship between the sensor and the tone ring. This confuses the sensor into thinking the wheel is locking up and therefore releasing the pressure in the brake caliper (anti-lock). The little bit of rust probably raised the sensor in the knuckle a couple thousanths of an inch causing the problem. He told me he sees this problem more often in Chevy trucks, but occasionally in Fords. Before I took the truck to him I had tried everything I could think of to cure the brake pull including bleeding the ABS unit multiple times (using FORscan), multiple brake bleeds, replacing parts, etc. Perhaps something worth looking at ??

P.S. He was able to carefully remove my ABS sensor and re-use it. He told me 9 out of 10 will break when trying to get them out.... so perhaps plan on a new sensor.