ABS comes on when truck comes to a creeping stop

[swak6287]

Replaced rotor, pads, and spindle, and Xterrain tires. now, when driving normally, stops normal untill it slows down to a creep....and u feel the nobbies on the tire....still having the foot on the brake... and all of a sudden the brake padel sinks to the floor and u feel the tapping on the padel.
i sprayed the sensor with the brake cleaner to clean it and there is little streaks of black thingy on it that i did not other to wipe off. shold i had totally wipe that thing clean (sensor)? or u thin it could be air in the brake system? but the brake is not spongy at all.
anyone has any clue?
so, it brakes normally untill it comes to a creep, then the padel sinks to the floor 1/2 way and it begins to tap till i completely stop.

 

[swak6287]

TTT anybody??

 

[outhouse]

Sounds similar to a problem I had - ABS cycling at low speeds on good surfaces but only when manouvering.

Turned out to be the front ABS sensors.

After both sensors were replaced (the sensors were $216(USD)+Tax didn't pay for fitting as I had been so many times about the same problem!!) got 2 miles up the road and the problem was back.

Back to the shop which claimed that one of the NEW sensors was faulty. Picked the car up and the mechanic came along on a test drive - half a mile down the road the problem was back. Red faces all round!

I took the Ex home. Strange but true the problem happened only that once and never happened again! No further work was done on the car.

I was convinced that my ABS problem only started after I'd had the front discs and pads renewed.

So it's very possible that the ABS set up was just poorly replaced and/or connected up!

 

[swak6287]

ok, i will try to remove the sensor and wipe it clean. see if that helps.

 

[Rhett]

While you're at it, I would check the exciter ring for damage. It is behind the rotor, and the front ABS sensors use it to send signals as the wheels rotate. Looks like a toothed ring on the back of the rotor.

Also check the rear ABS sensor. On my truck it's screwed into the rear differential. If the rear sensor is worn out or dirty it will lite off the ABS light.

 

[swak6287]

actually, no ABS light. rotors are new... the exciter ring is good cause we looked at it before installing. would the ABS acting up has anything to do with the rotor and pads beig new and waering period?

 

[Rhett]

What about the rear sensor?

I have never heard of new pads/rotors causing that. Except in the case that a rotor was warped badly, then yes, it can throw off the front ABS sensors. But it has to be pretty bad. I think if that was your problem you would already know it from pedal vibration. So no, I've never seen new pads/rotors doing this, if it's all installed properly.

Did the ABS sensor get moved around any? On a 1st gen there is a metal "housing" that holds the sensor in place. It's held in place by two screws. If one or both of these screws come loose, or are put back in an improper position (it doesn't have to be off by much) then it can cause the ABS problem by being mis-aligned with the exciter ring. I'm not sure of the 2nd gen setup but if the 2nd gen ABS sensors are held in place this way, I'd just make sure they haven't moved or shifted a bit.

 

[Rhett]

actually, no ABS light. rotors are new... the exciter ring is good cause we looked at it before installing. would the ABS acting up has anything to do with the rotor and pads beig new and waering period?

Oh yeah, I meant to also add that I believe the ABS is supposed to turn off below 5 mph. Since yours is doing odd things *below* 5 mph then that strikes me as odd...I'd search on that topic...maybe there is a switch that controls this, but I am not sure.

 

[Eneurb]

Pay attention to which way the steering wheel pulls when this is happening. If it pulls left, your problem is in the right front and vice versa. Problems to check for are excessive air gap between the sensor and tone ring (should be about 0.015"), loose wheel bearing, damaged sensor and such. I have run into some really weird abs problems in the past with aftermarket rotors having the incorrect number of teeth on the tone rings, but that is one of the last things I would suspect. Problems like that don't set a code, because what the abs module sees is a difference in wheel speed, so it performs what it believes is a warranted abs event. Abs systems do not turn off below 5mph.

 

[outhouse]

Mine pulled to one side which made it less likely that both the sensors were shot- so I'm back to putting it down to setup.

 

[TSTONE]

Almost always a wheel speed sensor - what happens is one will drop lower then the other (ie: left reads 5mph while right reads 10mph), then the abs kicks in. It's a common problem, and potentially very dangerous. There is a bulletin somewhere about how to attempt to clean the sensors, but from what i've read if it works at all it'll only be temperary. Your best bet (after getting it confirmed using a ford ngs unit) will be too either replace the bad sensor or pull the abs fuse to dissable the system.

 

[swak6287]

the ABS fuse also controls the speedo. unless there is another ABS fuse tht i am unaware off. mine is a 99.

 

[Rhett]

Abs systems do not turn off below 5mph.

Are you certain that *ALL* ABS systems stay active at extremely low speeds?

I could swear, and I usually have a good memory, that I read on this site a long time ago that the 1st gen ABS and RABS systems are inactive below a certain speed. Of course, that could have been bad information...
At any rate I'd like to know for certain; I guess this info could be found in one of those ABS service manuals, specific to the model(s) in question.

 

[Eneurb]

I am refering to the 4WABS system on the Explorer. Perhaps RABS doesn't work that way, I'd have to look into it.

 

[351wExplorer]

get rid of the abs and just drive with your head on striaght

 

[swak6287]

that is what i ended up doing. pulled a fuse in the engine compartment. now, no omre ABS. yes, head is straight.

 

[Rhett]

People drove for years without ABS. If you know how to drive a rear-wheel drive vehicle (and a lot of people these days don't) in a skid then you can drive without ABS.

 

[outhouse]

That's all very true and you should be able to disable it in snow as you need to build up a plough ahead of the front wheels to help stop you.

But what will your insurers make of you pulling the fuse on your ABS should you ever slam into somones rear end?

 

[swak6287]

i just plug it back in.. i use to drive a 1978 corolla.... and that care still runs.

 

[gijoecam]

People drove for years without ABS. If you know how to drive a rear-wheel drive vehicle (and a lot of people these days don't) in a skid then you can drive without ABS.

Just because you can, doesn't mean you should.

I love how people think that they can threshold brake all the time better than the ABS system. The only time you can stop faster without ABS is in doow, soft snow, loose gravel, and deep, soft sand where, as you mentioned, the surface piles up in front of the wheel and it digs in. However, in those cases, you will have ZERO steering control, and will not be able to avoid hitting the onject if you can't stop quick enough.

With ABS, you Stomp, Stay, and Steer. Stomp on the pedal. Stay right there, don't move your foot or try and modulate it. Let the computer do it as there's absolutely no way you can stop any faster than you already are. Steer around the object in front of you. ABS doesn't re-write the laws of physics, it just lets you maximize your use of them. You still need a certain stopping distance for any given vehicle, ABS-equipped or not.

-Joe