ABS buzzing pedal while stopping - Ford Explorer Forum - Forums for Ford Explorer Enthusiasts
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Old 12-11-2019, 03:19 PM   #1
raschwar
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ABS buzzing pedal while stopping

On my '97 XLT, if I'm stopping slowly I hear what I believe to be the ABS being applied just before I come to a complete stop. I don't feel anything except maybe a very slight pull to the right but can hear the module buzzing. There's no ABS light and it doesn't happen if I apply the brakes hard. No faults in the traction module and the ABS light does flash during a test.

Wheel sensor?

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Old 12-24-2019, 06:52 PM   #2
J_C
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Maybe. Could be a bad sensor, its pigtail wire, the connector, or the wiring harness to that connector. Could instead be a bad hub bearingthrowing metallic goopy grease up on the sensor if it's AWD or 4WD so the sensor is in the hub.

If it's the latter you can try removing the sensor and cleaning it off, and cleaning goop out of the sensor ring inside but it would probably just get fouled again and the sensor might break trying to remove it after all this time.

Then again it could be the rear sensor, a scan tool capable of ford specific live data should show wheel RPM for each of the two front and the one rear, differential mounted sensor. An ELM327 dongle connected to a device running Forscan app will also show wheel speed sensor data.

if it's the front hub and you haven't replace it in recent years (or did but used a generic lower quality hub), it's probably due to have the hub replaced and they come with a new sensor. Once one hub is bad it is probably nearly time to do the other one too. I like the Timken on Rock Auto, best bang for the buck IMO to have Timken bearings in them.
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Old 12-25-2019, 09:21 AM   #3
raschwar
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Thanks J_C, I'm going to disassemble the hub and clean the sensors as soon as my replacement dust shields show up. I'm also replacing the master cylinder and servo as the pedal feels a spongy, even after bleeding, and there's a "whoosh" when I step on it. All original so, about time.

It seems that my diag tool doesn't do live brake info but I the truck pulls a little right when ABS kicks in so I'm hoping left front.

Rich
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Old 12-25-2019, 09:53 AM   #4
J_C
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By cleaning the sensor ring I meant just manually taking a pick and scraping "much" of the greasy goop out of the valleys between the sensor teeth, one by one as you rotate the wheel, for an AWD or 4WD hub where it's in the hub. Tedious, but you don't want to spray a solvent inside the hub since the bearing seals may not be intact to keep that out of the bearings.
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Old 01-01-2020, 08:57 PM   #5
raschwar
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An update on my '97 XLT. The brake servo is replaced. The master cylinder was fitted but I'm going to take it off and bench bleed it. I started working on the left front wheel. When I pulled the caliper it was pretty rusted, including the pistons, one of which seemed to be sticking. I was going to rebuild it but decided to just replace both calipers. The wheel sensor was pretty gunked up but the ring looked good. Since I don't want to do this twice I am also replacing the sensors. Everything should arrive on 1/3. It's a little cold but I'm having fun.
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Old 01-08-2020, 11:13 AM   #6
raschwar
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I got everything installed and the ABS problem is gone but... when the engine is started (creating vacuum in the booster) the pedal goes WAY down. The vehicle does stop and I can even get the ABS to kick in on a loose surface. I bench bled the MC and vacuum bled the lines. The pedal is fairly firm but does move down slowly with engine off.

I've gone through over a quart of fluid bleeding. I don't see any leaks but I do still see some bubbles in the fluid. Am I just not bleeding enough?
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Old 01-17-2020, 09:41 AM   #7
raschwar
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I've bled and re-bled and still the pedal goes to the floor when I start the engine. The brake pedal is rock solid when the engine is off but as soon as the booster gets vacuum, no pedal. Only at the very bottom of the stroke do the brakes work.

I adjusted the push rod length on the booster but it was not that far off and it still doesn't work.

What else? hoses?
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Old 01-17-2020, 03:43 PM   #8
J_C
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I'd guess booster or vac leak.
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