Another ABS Mystery

[fliflicker]

I was returning from a trip and my front brakes started to squeel a bit. Well the closer I got to home the worse it got, till I was a little metal to metal. Dumb I know... anyway with 90k of my own miles I figuered time for a nice overhaul and replaced the rotors, pads, berrings, seals the works. Felt nice to have everything cleaned up and new. Upon test-driving, as I came to a stop, my brake pedal started pulsing and making a groaning sound. It also pulled to the left in concert with the pulsing as if only the front left wheel was being affected. I pulled everything apart and began the following saga...
- Cleaned and double checked everything and put back together. No change
- had the rotor turned, put back together. No change
- Took it to a local mechanic who I am on a friendly basis with. He changed the sensor. No change
- He changed the other sensor. No change
- He changed the ABS unit. No change
- He replaced the rotor. No change
- He replaced the calaper. No change
- He called me to say he was putting all my old parts back on and that I should come and take the car away (no charge)
- He suguested I take it to a Dealer (yea right) :/
Its a 1994xlt 2WD
Any suggestions?

 

[Robb]

Pull the ABS fuse and see if it acts the same.

 

[fliflicker]

Works fine when fuse is pulled...

 

[Rhett]

You said, "changed the ABS unit".

Is this the proportioning valve or is this the ABS computer?

 

[DeRocha]

First welcome to the site and lets see if we can solve this mystery.
The ABS hydraulic unit and controller are big $$$. The sensors are not cheap either..
If I'm reading this correctly you indicate the brakes worked fine, up until your service them correct? After servicing the brakes the ABS comes on and pulls left (indicating ABS is pulsing the right wheel). It definitely sounds as if the wheel sensor is indicating a lock up condition to the ABS controller for the right wheel. ABS rotors have exciter rings, do your new rotors have them? Did your bleed the brakes (if so how much and what condition was the fluid in)?

 

[fliflicker]

Glad to find you folks! what a great site!
Looks like I wasnt very clear.. Sorry! The pulsing occured immeadiately after changing the rotors, pads and bearings. Soon after, the ABS light came on. While the ABS light was on, the breaks appeared to work fine. The next day when I went to take it to the mechanic the light was off and the pulsing had returned...
You mentioned a problem with the "right" wheel... Would that be the passenger side? the pulsing seemed to occur on the "Left" or Drivers side... I will check both to make sure the exciter rings are present... To be honest I dont remember if they were there or not. I guess I trusted the parts store EE. Probably my first mistake...
Both I and the mechanic bled the brakes. When I did them every thing seemed normal. (a slight drop in fluid which I filled after each wheel)

 

[DeRocha]

Orientation is given from the drivers perspective (ie the driver's side is left while the passenger side is right)
The ABS lamp comes on when the ignition is turned on for a bulb check, then goes out after the engine starts. If the ABS warning light remains on or comes on while driving, it indicates a fault has occurred in the ABS system.
You indicated the car pulled to the left when the ABS kicked in and you heard/felt pulsing.. Did your brake fluid look brown/bad when you bled it? Are you running larger than std tires?

Not related but for autohubs did you seat the wheel bearing nut after you installed the new rotors? It should have been torqued to 35ft/lbs while you spin the rotor by hand. Back off a 1/4 turn and then torque to 1.4 ft/lbs = 16 in/lbs.

 

[fliflicker]

Abs

Fluid looked good... std tires... I'll have a chance to pull tonight and check all again. I will let you know what I find...

 

[GSEREP1]

Hello,
As I said in my post, I did the exact same thing last week. I changed original rotors on my 97 Explorer 2WD 5.0L V8. As SOON as I backed up and started forward, I got the ABS light. My car also pulled STRONGLY to the drivers' side.

I took everything apart and discovered that the exciter ring on the drivers' side rotor cut a gouge in the sensor. These are aftermarket Pep Boys rotors. I always used FORD rotors in the past. There has to be something common about all these problems once the rotors are changed. I am about ready to remove all the pep boys stuff including rotors pads and wheel bearings and return it to the store.

I don't mind spending the extra cash if it makes the car work right. You mentioned something about bleeding the brakes. I did not flush the system, or open the bleeder screw. I slowly pushed in the dual pistons with a "C" clamp like I always have. This is not the first time these brakes have been done. There has never been a problem in the past. The only variable this time was the use of NON-Ford parts.

Anyone have a suggestion?