When turning vehicle and braking at the same time. Feel shutter

JMSUAREZ

MEMBER
2001 FORD EXPEDITION
115,000 MILES

A few days ago I replaced both upper control arms/ball joints, installed new front rotors, brake pads, and bearings. Also had front end alignment and tire rotation and balanced. Before I did these repairs the vehicle was fine other than needing new brakes and ball joints. Now here is my problem now, while going straight everything works great, but if I'm lets say pulling into the driveway, turning and braking at the same time I feel a shutter in the brake pedal. It feels almost exactly like the ABS is working. But I have no ABS light come on, also no rain or snow on the ground. So it's seems like it was something I messed with or could it be just a heck of a counsidence.
Help

4 Replies

CARADIODOC

MECHANIC
33,871 POSTS

I think I'd start by pulling the fuses for the ABS Computer to verify that is what you're feeling. If the shudder stops, look at the two front wheel speed sensors. Anything that reduces the signal can cause activation at low speeds when those signals naturally get weaker. Electrically the sensors are fine so no fault code will be set and the warning light won't come on. The loss of signal mimics a wheel that is locked up while you have the brake pedal applied.

Rust on the end where the magnet is can weaken the signal. Working on the brakes can dislodge some rust and scale, and some crumbs might have stuck to one of the sensors.

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Friday, March 23rd, 2012 AT 2:56 AM

CARADIODOC

MECHANIC
33,871 POSTS

Also look in the area the arrow is pointing to for rust buildup under the sensor's mounting tab. GM uses a similar design on many of their trucks and they have a big problem with rust buildup there that pushes the sensor up. That increases the air gap and weakens the signal. The tone ring is built into the bearing just like on GMs, and theirs is not very substantial. It doesn't take much to have ABS activation at inappropriate times.

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Friday, March 23rd, 2012 AT 3:08 AM

JMSUAREZ

MEMBER
3 POSTS

First I pulled the ABS relay out, of course the ABS light came on. I took the vehicle out and found that it did not shutter at all turning and braking in any direction. So this lead me down the ABS path, Fuse good, Realy good, pulled each sensor out and yes, they were full of rust/build up, went through and cleaned them both well, also cleaned the area you had pointed out in the picture (beneath bolt placement) and made sure when I screws them in they both were flush. Test drove and the shutter was there when I turned to the right and braked at the same time. When through and tested/checked everything again, but this time checed the connectors above the wheel well in the engine compartment and they were nice and clean and tight. So Im at a loss, do you think one of the sensors is just bad?

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Sunday, March 25th, 2012 AT 9:31 PM

CARADIODOC

MECHANIC
33,871 POSTS

I never checked on a Ford but my friend just solved this on his GMC Suburban by cleaning the rust under the sensors. The right front wheel read around.500 volts at 10 mph. The left front one read only.330 volts so that's the one he started with. After he put it back together it was reading over.700 volts and the false activation was gone.

The strength of the signals is lower at lower speeds and if one gets low enough to be not recognized by the computer, it will think that wheel is locked up. My next recommendation would be to find a mechanic with a scanner that can access the ABS Computer and watch what each sensor is reading when the problem occurs.

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Sunday, March 25th, 2012 AT 9:42 PM