Short buzz sound when coming to stop

[sonoman]

I recently replaced the rotors on my 94 Explorer 5-speed manual. I am the original owner

I used rotors from a 1st gen Explorer from a junkyard...the junkyard rotors were never turned and in good shape. I cleaned the rotors, replaced the bearings, replaced the pads, and put it together like all the other brake jobs I have done on this Explorer. With the new rotors and pads the Explorer stops smoothly and appears to work properly during normal braking

Since the change there is a very brief 1-2 second buzz right when the vehicle comes to a complete stop. It is not the same as the pulsing you hear when the ABS activates...it is faster pitch and very short duration, plus it occurs only when the vehicle is moving very slowly and comes to a complete stop. The sound seems to come from low the engine compartment, like near the transmission hump in front of the shifter toward the firewall.

I suspect maybe the ABS. Maybe the rotors were not the same and the speed sensor "notches" (for lack of a better description) are different from the originals. A quick look when I replaced the rotors and they looked the same, but I didn't study them all that closely. All I did was replace the rotors and pads...I replaced the master cylinder a year ago and flushed the system with new brake fluid and it worked fine until I installed the new rotors.

Any thoughts on why the brief buzz when coming to a stop? How do I make it go away?


thanks

 

[FR-425]

Probably just the new pads breaking in. take it out and perform a few "hard stops" to run the pads in.

Smash the pedal full on emergency stop action. See what happens.

 

[sonoman]

It is not the pads. The pads are broken in and stop fine. It is an electronic buzz lasting about 1-2 seconds just as the vehicle comes to a complete stop. The buzz seems to come from around the transmission hump, not the brakes themselves. That's why I suspect something in the ABS. Maybe the ABS pump?

 

[Roadrunner777]

You could pull the fuses to the ABS system and figure out if this is related. If it is... well, the only thing you changed that is a part of the system is the rotors. I did some research, I don't think there are other rotors out there with different notches/fins. The 93 and 94 take the same rotor part number, and anything earlier isn't ABS. 95 and newer take a different rotor, but I'm pretty sure you would have noticed that, assuming you pulled them yourself. If someone else pulled them... I mean, the junkyard around here, they could make that mistake easily.

Does the buzz continue even for a brief moment after the wheels stop? Does the buzz get louder/softer, higher pitch to lower pitch?

You would have said if the ABS light was on... yeah, I'm reaching. Pull the fuses. It's 2 minutes and will narrow your search dramatically.

 

[sonoman]

Yea, I will pull the fuses. My son has the vehicle now

I pulled the rotors myself. I didn't check the VIN for the date but it was a Gen 1...not a 95...and the notches/fins looked like my 94.

The buzz occurs just as the wheels stop and there is no change in pitch. It is kind of like the buzz the washing machine makes when the cycle is over...just a brief buzz for a second or so. It is electronic (or electronically driven) and it happens right as the vehicle comes to a stop

 

[Roadrunner777]

I have a factory wiring book, there is one thing electronic right at the transmission hump... the warning buzzer/chime module. I have no way to connect the two events, but it's just something to note.

You know what else I might do before I got too far into this? If it's really electronic, I just might disconnect the battery for 10 minutes and let the electronics reset. I might do that before trying anything else.. it's easy and if it goes away... voila!

If you can remember, check something for me please... check to see that the ABS light comes on with initial key-on and goes off when you start the engine? I want to know that the light is working and there is no error in the ABS computer.

 

[sonoman]

Thanks for the info on the electronic module on teh transmission hump. Not sure if it is related though...and the brake sound isn't like the door chime but I can poke around.

Great suggestion on the battery. I won't be able to get to the vehicle until next weekend but I will try the battery and the ABS fuse when I get back.

 

[RangerX]

If you pulled rotors from a 91 or 92, they would still fit and bolt up fine and otherwise operate normally, but wouldn't have the abs sprocket on the inside side of the rotor hub.
Maybe the buzz is the computers reaction to sensing the sprocket is not there?

 

[sonoman]

the boneyard rotors have the sensor sprocket (I described them as the notches or fins earlier)

My son said the ABS light on the dash lit up today. Not sure why it would fail coincident with rotor swap, though.

If I pull ABS fuse will the dash light go out? I know if I disable ABS if drops back to no-ABS in fail-safe. I was told ABS parts for these vehicles are not available...maybe just boneyard

 

[Roadrunner777]

Yes, pulling the fuse will take care of it. There may be more than one, but it will be obvious... I think there is a relay too.

I'm not a big fan of this generation ABS. I pulled the fuses after the ABS took over the brakes and almost put me off the road. I know how to drive on snow and ice.

Now, all that said, if you want to hold on to the ABS, you can read codes off the ABS computer. There's a thread on that somewhere. Take a look, I'll see if I can find it in the morning.

 

[sonoman]

how do I ID which fuses or relays to pull for the ABS?

 

[Roadrunner777]

Everything you want to pull is in the fusebox under the hood (power distribution box). When you open the lid, there will be a legend on the underside of the lid.