Troubleshooting ABS problem

[hal keiner]

I recently replaced the pads and rotors on my 2002 Sport Trac front wheels. I bought PBR brand rotors and some good quality disc pads. However, after the replacement the front brakes started to slip/jerk when braking at a slow speed. After researching this symptom on this forum, it was suggested that I pull the fuse for the ABS and see if the slipping/jerking went away. It did and so this seemed to confirm that that the ABS is at fault. The thing is, I have no idea what part of the ABS may be at fault. I do not have a ABS code reader to do a proper diagnostic troubleshooting of the ABS. I hesitate to buy an ABS code reader as they seem to cost several hundred dollars or more.



I have further read that there are several possible ABS failures that can cause these symptoms . These are listed below:



1) Bad tone ring on the new rotors

2) ABS sensor is dirty

3) ABS sensor has failed

4) Wiring from ABS sensor to control module is broken/failing.



I am not an avid part swapper to troubleshoot. I prefer to use a more systematic approach to narrowing down the problem before replacing a part. So without replacing expensive parts to see what happens and without having an ABS code reader, what type of diagnositics can be suggested to narrow down the problem further? Narrowing it down to an ABS fault is already good progress for me.



Below is a picture of my old rotors with an arrow pointing to what I think is a tone ring. Is that right?



Also, I assume that PBR brand is a good quality and it is unlikely that the tone rings on these new rotors are bad. Is that a good assumption?



Thanks in advance for any advice.



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[Ed Fenwick]

Aloha,

I am sure that someone here has more experience than I,but. I would check all the wires and plugs in the area that you were working. Does the truck show any codes?

Good luck Ed

 

[EddieS'04]

Did you open the caliper bleeders when pushing the pistons back? Dirty fluid can damage the ABS unit. Sensor maybe out of position. compare the old tone ring to the new one.

 

[Kevin Palmer]

A common fault is, the toner ring id DIFFERENT than the original. Unfortunately, you are going to have to pull off one or both of the rotors and compare the toner rings to the OEM you pulled off.



It all has to do with the spacing of the ribs, the exact same number of ribs, that kind of thing.



If they are different, and I suspect they are, then the ABS system is thinking you are skidding virtually all the time as the pulses it is getting are different either front to rear, or left front to right front if only one of the front rotors has an incorrect toner ring.



And yes, your arrow is pointing to the toner ring.

 

[scott degroot]

If you let go of the steering wheel while it is acting up will it pull to one side or the other? If it does it will at least give you an idea of where to start looking. If it pulls to the left then look at the right side adn vice versa. The reason being is that if the abs is falsely activating then it is releasing one of the brakes, when it does this the vehicle will pull to the side that the brake is still applied on..or the side that isn't having an issue. If it doesn't pull at all when the problem occurs that means that both sides are operating equally which more than likely means that the tone rings on the rotors are to blame.

 

[hal keiner]

Thanks for the responses. I've got a lot to think about now.



I figure I should first do the "let go of steering wheel" test, as suggested by I1tech, to see if there is a pull to one side or another. I can do this test without removing the rotors from the truck. Depending on what the above test shows, I'll have to decide which rotor (if not both) to remove and compare with my original OEM rotors.



If the tone ring is at fault, is it obvious to see that the tone ring is different than the OEM rotor? I understand the obvious part about counting the ribs, but the part about looking at the size of the ribs is not clear to me. Would be differences be visually obvious or are we talking about using a micrometer/caliper to measure things to the nearest .001 inch?



Pulling the rotors is a pain so I figure I might as well know exactly to look for if I do that. I don't want to pull them more than once. I might even consider putting the old rotor's back on to see if the problem goes away. I figure it will just cost me the price of buying new inner seals each time I remove the bearings from a rotor.



Regarding the ABS light on the dash, it acts normally. It lights up only at startup for a few seconds and is off when the truck is running.

 

[Kevin Palmer]

Once you remove the outter bearing, put the nut back onto the spindle. Then

Slide the rotor off allowing the inner bearing to hit the nut, thus popping the

seal off using the bearing itself with no danage to the seal in most cases.

 

[hal keiner]

Thanks for the tip on removing the seal without damage.

 

[hal keiner]

I did the "let go of the steering wheel" test and the car definately pulls to the right.This tells me that the left wheel is likely the only problem wheel rather than both wheels. This is good news, as it tells me that my new rotors probably do NOT have bad tone rings and probably do not have to be replaced.



Now that I narrowed the brake problem down to only the left wheel ABS and accept that the rotors are probably OK, I am going to next pull the rotor off and inspect and clean the left wheel ABS sensor. Hopefully that solves it. If that does not solve it, I'll get back to this forum and ask for some more advise, if there is any left.



Thanks guys...

 

[hal keiner]

Well, I cleaned the ABS sensors on both front wheels and my braking problem still did not go away. It is now my conclusion that the new PBR rotors that I recently put on the truck are faulty. Bummer.



I could have suspected the new rotors immediately after replacing them, but since I had also replaced the pads I was not sure if I had messed something else up when doing the brake work. The symptoms were typical of dirty ABS sensors, so I gave that a try. It didn't help. I did some testing of the sensors with an ohmmeter and voltmeter but the results were not conclusive that a sensors was bad. That is when I put the old OEM rotors back on and found that the ABS works fine with them back on. Most likey bad tone rings on the PBR rotors, as suggested by Coastiejoe in a previous response.



I hesitate to buy another set of rotors without polling a few users on this forum as to what a good brand of rotor is, so that I don't have the same problem again. I paid $120 for the pair of PBR rotors online. Is it too much to expect to get good rotors for that kind of price? I am just a normal commute driver and don't want or need high end performance stuff.



Any suggestions???

 

[scott degroot]

Why did you replace the rotors in the first place??

 

[Tom Schindler]

I used Napa Rotors. They were about 100.00 each, but they were made in Canada as opposed to the Chinese crap.



The Napa Ultra premium are now made in China and they now are also crap.



This is not an assumption, I have Canadian ones on my Trac and Chinese ones on the Explorer. Same brake pads. The Explorer rotors have warping issues, the Trac rotors don't. Complained about it at the Napa store. Guys said that they have had many complaints about them and the sales of the ultra premium ones have just about ended.





Tom

 

[hal keiner]

Why did you replace the rotors in the first place??

The pads were worn out and the OEM rotors needed to be turned (machined) due to some grooving and such. Rather than gettng them turned at a machine shop, I thought it quicker and easier to just replace them. This way I could do the job all at once, instead of removing the rotors, bringing them to a machine shop, and then putting them back on the truck. Also, I have only one vehicle and I am not too close to a machine shop, so the logistics of getting the OEM rotors turned was not so good.



While I understand that you usually get what you pay for and that the PBR rotors were not the best rotors available, I did not expect that they would cause ABS problems and thus not be usable at all. Lesson learned...

 

[scott degroot]

Looks like it's time top get the original ones resurfaced. You do realize that you don't need to go to a machine shop to have this done. Just about any place that works on cars should have the ability to resurface rotors..if they don't then they have no business working on vehicles.

 

[hal keiner]

Problem solved...



I brought my old original OEM rotors in to the shop to be turned but they were worn below specs so I could not use them. I returned the new PBR rotors and bought some new Raybestos Premium rotors instead (for about the same price). The ABS system works fine now. I was either unlucky to get one bad rotor in a batch of manufactured PBR rotors or choosing a "better" brand of rotor does make a difference. Go figure.

 

[Kevin Palmer]

The toner rings only has to be off a minimal amount. It all comes down to differences..



When all things are rolling along (no brakes) then the ABS does not care about the toner rings. Tranny does not care as it uses a separate sensor and wire feed to the ECM/PCM (unlike some of the Early versions where the tranny was always compared to the ABS reading to compare speed readings).



Sooo, once you press the brakes, the sensors send the signal to the ABS brain and or ECM/PCM on some models. THE brain looks at all four, in some cases three, signals. If they all read the same with something like a 1% difference all is well. But,,, if tow say it is going 30 MPH and one says it is going 25 MPH, it thinks that tire or axle is skidding. Thus,, it pulse the other two brakes.



So like I said, it is a matter of differences, and when the toner rings are not correct, there will ALWAYS be a difference.



At least you got it fixed...



No fun figuring that stuff out is it?

 

[hal keiner]

Yes, the advice I got on this site helped me to figure it out without incurring any extra costs. I just had to return the PBR rotors for a refund and then buy some other rotors. In the end it seems a simple solution, but it is not when there were many other possible causes to consider.



I think that if I gave up and brought the truck to a repair shop to troubleshoot, it could have cost me significant money. I would have been charged labor costs and perhaps also have been told to replace the ABS sensors. I can't be sure of this, as I didn't do that, but you can't do better than figuring out the problem yourself and not paying anything extra to solve it.



Thanks to the many the provided advice.

 

[Jason Barnes]

I have a similar problem to this, but it only happens when my ST sits outside for a few hours while it's raining. I only have the problem when I first start it up and go to the end of the parking lot, drive way, etc. I lightly press the brakes and they lock up. A temporary remedies that I have noticed for this problem is that if I lightly press the brakes while driving down the road right after I have the problem the next time I go to stop it does fine and doesn't lock up. Then the next time it is outside while it is raining I have the same problem again. Please help!