J_C
Explorer Addict
- Joined
- July 30, 2009
- Messages
- 6,395
- Reaction score
- 2,383
- City, State
- Florence, KY
- Year, Model & Trim Level
- 1998 XLT 4WD 4.0L SOHC
Having air in the ABS pump would not cause this. The ABS only activates if there is a wheel speed imbalance detected. You could have nothing but air in the ABS module and that would not cause ABS to activate when it shouldn't. Since you don't have the ABS light on, in theory the system can see the abs sensor is there, so the question is when is it not providing a good signal.
At this point I would try braking from faster speeds on good/dry pavement, not trying to lockup the wheels at all. If ABS activates while still going over 15MPH, in other words it always comes on when braking, or at least at any speed, you could have a wiring issue or the connector, either at the sensor end or the abs module end.
If ABS does not activate until going slower, this suggests a weak signal. If we can assume that after trying two sensors, one of the two must be good, this leaves distance and reluctor ring contamination, or less likely, a corroded connector or frayed wire (least likely).
Distance, possibly badly worn bearings, or a rust buildup where the ABS sensor mounts so it is sitting too high. You could plug the hole and remove the rust if the sensor gap is too great. Contamination, I don't recall if you mentioned whether you have RWD or 4WD/AWD, that should be in your sig or profile so people can see this! Okay now I see you mentioned replacing the hubs.
With a hub internal reluctor ring, it could be contaminated with grease that has metal particles in it due to the hub bearing failing or that grease gets slung up on the ABS sensor, so you put a new one in and same contaminated grease gets flung on the new one too. I would not rule out the hub even though it is fairly new, rather would check it. How about using a paintbrush down in the sensor hole to try to get as much grease as possible out of the reluctor ring teeth and wipe off the end of the sensor?
If you have the means to get all drive wheels off the ground, you can measure for the AC low voltage signal coming from the ABS sensors as the wheels turn. If you can't spin them fast enough by hand then let the engine do it. A multimeter can do this but a scope would be better to show the waveform from them.
At this point I would try braking from faster speeds on good/dry pavement, not trying to lockup the wheels at all. If ABS activates while still going over 15MPH, in other words it always comes on when braking, or at least at any speed, you could have a wiring issue or the connector, either at the sensor end or the abs module end.
If ABS does not activate until going slower, this suggests a weak signal. If we can assume that after trying two sensors, one of the two must be good, this leaves distance and reluctor ring contamination, or less likely, a corroded connector or frayed wire (least likely).
Distance, possibly badly worn bearings, or a rust buildup where the ABS sensor mounts so it is sitting too high. You could plug the hole and remove the rust if the sensor gap is too great. Contamination, I don't recall if you mentioned whether you have RWD or 4WD/AWD, that should be in your sig or profile so people can see this! Okay now I see you mentioned replacing the hubs.
With a hub internal reluctor ring, it could be contaminated with grease that has metal particles in it due to the hub bearing failing or that grease gets slung up on the ABS sensor, so you put a new one in and same contaminated grease gets flung on the new one too. I would not rule out the hub even though it is fairly new, rather would check it. How about using a paintbrush down in the sensor hole to try to get as much grease as possible out of the reluctor ring teeth and wipe off the end of the sensor?
If you have the means to get all drive wheels off the ground, you can measure for the AC low voltage signal coming from the ABS sensors as the wheels turn. If you can't spin them fast enough by hand then let the engine do it. A multimeter can do this but a scope would be better to show the waveform from them.