ABS Brake Question

[tdapsr]

2000 Explorer 2WD with ABS. I just replaced the front wheeel bearings, hub rotor assembly (Napa Premium) on the front (both sides) and installed new brake pads (semi metalic). I also completely flushed the brake fluid (front and rear) starting with the right rear, left rear, right front, and left front. Now once in a while usually when my speed is very slow (around 5 miles an hour and i depress the brake petal the ABS kicks in. I re-bled the system and it still does it. Any one know what may be causing this?

 

[96eb96]

2000 Explorer 2WD with ABS. I just replaced the front wheeel bearings, hub rotor assembly (Napa Premium) on the front (both sides) and installed new brake pads (semi metalic). I also completely flushed the brake fluid (front and rear) starting with the right rear, left rear, right front, and left front. Now once in a while usually when my speed is very slow (around 5 miles an hour and i depress the brake petal the ABS kicks in. I re-bled the system and it still does it. Any one know what may be causing this?

Since you changed the hubs, it is more than likely you disturbed the wheel abs sensor in the hubs. The abs light has nothing to do with brake flushing. If the hubs came with new ones one is probably bad or not seated correctly.

 

[tdapsr]

When I said the ABS kicks in i meant the ABS kicked in I wasn't refering the the ABS light coming on. But I did a search on here and came up with the sensor subject too. I removed them and they both had some globs of grease and brake dust on the faces so I cleaned them off. I haven't test driven it yet so we'll see. Thanks

 

[96eb96]

When I said the ABS kicks in i meant the ABS kicked in I wasn't refering the the ABS light coming on. But I did a search on here and came up with the sensor subject too. I removed them and they both had some globs of grease and brake dust on the faces so I cleaned them off. I haven't test driven it yet so we'll see. Thanks

sorry , meant brake bleeding has nothing to do with abs activation. the debris on the sensor was tricking the computer into thinking the wheel stopped moving at low speed, thus the ABS is actuating. Its tricky because the system will never generate a code or light the ABS lamp cause it thinks there is a legit reason to trigger the abs.

please report back if there are further issues.

 

[tdapsr]

Thanks. I suppose I could have worded that better. I test drove it and it was still doing the same. The system modulates when traveling at very slow speed (under 5 mph or so) and does it when the brakes are initially applied. I just finished removing the calipers, and rotors and cleaning everything off. I had left some smudges of grease residue on the reluctor wheels as well. It was however a hell of a lot cleaner than the old reluctor wheels that came off of there and it was functioning properly. My son is test driving it now. Thanks for your help. I appreciate it very much.

 

[tdapsr]

still modulating at low speed

After breaking everything down and making sure all was clean the brakes are stiil modulating at low speed. The senors were not damaged or disturbed during the process. I'm wondering if it's someting with the material the reluctors or made of. Even though they are Napa premium rotors, they were made in freaking China. It doesn't pull to either side, it just seems like it takes the system too long to recognize wheel movement at slow speed.

 

[tcwc]

Same exact problem..

I have a '95 that does exactly as described. Low speed, <5 mph, the brake pedal modulates (ABS kicking in). No ABS lights on the dash.

I read in other posts that replacing the REAR differental ABS sensor cured the problem. Did that, and I still have the problem.

There may be an ever so slight pull to the left when mine has the problem (pull to the left when the brake pedal / ABS kick in @ < 5mph).

I noticed that some guy is selling hubs W/ABS sensors on ebay...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=360041940884

These seem to be below the going rate for JUST hubs, not mentioning including the sensors! Has anyone tried these??????? From a financial standpoint, it would pay to get these hubs even for just the sensors!

Any ideas or comments would be appreciated!!! Thanks. Cheers!

 

[96eb96]

Oh, you have a 2wd so the setup is a bit different. but those hubs in the last post are more than worth it just for the sensors! I was thinking about 4wd where the sensor is integral to the hub, sorry.


Still, As for the pedal pulsation, a shop has a special scanner that can monitor wheel speeds, so they can tell exactly which sensor is reporting lockup.

The other troubleshooting tricks are disconnecting the sensor, and connecting it to a DVM:

- check sensor continuity (ohms) while wiggling parts of the sensor wire. You may find that at some point the sensor shorts or opens

- check sensor A/C voltage output. lift up the wheel a bit, and spin it while monitoring voltage. If the sensor zeros out before the wheel stops you have a clue. You can compare both sensors and see which one looks suspect.

 

[tdapsr]

Yeah, the analism in me will prolly have me doing all of that. But I could just pull the fuse and be done with it. It seems strange that the problem began at exactly the same time as the brake job. I read somewhere in here that the highway traffic safety administration reported more fatalities with ABS than with out ABS. Now, is that because people don't know how to use ABS (stomp and hold) or is that because there are more cars equiped with ABS today than not. Kinda like "more kids choke on hotdogs than any other food". Well kids eat more hotdogs so of course they choke on hotdogs more.... Just an early morning thought.

 

[96eb96]

Yeah, the analism in me will prolly have me doing all of that. But I could just pull the fuse and be done with it. It seems strange that the problem began at exactly the same time as the brake job. I read somewhere in here that the highway traffic safety administration reported more fatalities with ABS than with out ABS. Now, is that because people don't know how to use ABS (stomp and hold) or is that because there are more cars equiped with ABS today than not. Kinda like "more kids choke on hotdogs than any other food". Well kids eat more hotdogs so of course they choke on hotdogs more.... Just an early morning thought.

Another reason for those stats are because people become very confident with ABS, they do not at all make you stop faster, but rather keep you in control and prevent spinning out from wheel lockup. I tried it in the snow without abs(disconnected a sensor to test) and its not fun, even when pumping the brake. Ford didn't even make it an option on the ex, and they do to this day on a lot of their cars. I was in a showroom and I saw a 2008 v6 mustang with no ABS or TC! And as you see I don't live in Florida. The explorer isn't exactly a sportscar, so I would probably feel a bit more at ease with the ABS.

As for the problem happening after doing brakes, I had a problem just like that on a Thunderbird, the mere act of hyper extending the wheel when doing brakes may be just enough to disturb a failing sensor.

Then again, it may be a total coincidence and there could be another issue at bay....but you have something to go on there...

 

[tdapsr]

After speaking to a Ford mechanic he was pretty confident it was a problem with the reluctor wheels on the new rotor hub assembly. Possible damage to the reluctor wheel while installing the new wheel seal. (A common occurrence he said.) Anyway he was right. I either disturbed it (which i doubt) or it wasn't installed correctly. At any rate I checked and repositioned the side I suspected and it turned out to be the problem. they work great now. Thanks all.