Front ABS 95 4WD

[thagan]

This is my first posting, I did wrong by putting in 911 sorry! I'm planning on buying 2 front ABS sensors. I replaced the rear one but ABS still activates while braking at slow speeds. Are there any other parts such as O-Rings or bolts etc that are recommended to replace at the same time? Also my understanding is that I need to remove the rotor and then the rotor shield to get to the sensor. Any help is much appreciated... Todd 95 4WD 79K

 

[Mbrooks420]

I think normally the fronts are cleanable. They are magnetic and pick up shavings and grime after a while.

 

[Hartman]

Yes you can remove them and clean them. You don't have to remove anything really. If you look on the back of the knuckle you will see the sensor held on with 1 hex screw. Just take that out and the sensor will come out.

 

[thagan]

I do not have to remove the rotors? I can only see a cable going through the back side. Thanks for your cleaning tip, I will try that first but I was going to buy sensors to have if needed but does anyone know if most dealers will refund unused sensors? They are so expensive! by the way, very sweet Pics! Thanks...Todd

 

[Hartman]

On second thought, you might need to remove the rotors so you can remove the dust shield. If you can't follow the cable back to the sensor on the back of the knuckle, then you will have to remove the rotor and dust shield.

 

[pax]

I had the same problem. There was nothing wrong with the sensors. It was the sensor mounting surface got heavy rust on it, the rust actually lifted the sensors up slightly, so the induction voltages from the pick up coil is lower when the wheels are turning slowly just before a complete stop.
I just removed the sensors and fitted a wire brush on a drill to clean up the mounting surface, it was working like a charm after. No more false triggers. I also had the same problem with my 97 AWD Astro Van, I did the same cleaning on the mounting surface, it also worked ok after.
This problem is a cash cow for the dealers, they are most likely would replace them instead of just cleaning it up and put the old ones back on. Since the scan tool would tell them it is a bad sensor.
By the way, you do need to remove the rotor and shield to accesss the hex bolt. Have plenty of liqid wrench, the sensors are really tight, there is an o ring on the sensor body, don't break it. You need a lot of patients to get that thing out of the hole. Good luck.

 

[thagan]

Before taking off the sensor, I scraped the rust around it but not where it is mounted. When I took off the sensor, I saw grease on the inside ring so I shot brake cleaner on it. Although it shot the grease out of the grooves, I can not get the fluid out because one of the hub bolts is locked. I put it all back together and the problem is still there. Tomorrow I am going to pay the big money and replace the sensors but maybe I should just try scraping the mount surface. Thanks for all of the help….Todd 95 4x4

 

[pax]

Todd,
Don't wast your money on the sensors. I am 99.99 percent sure it is the rust on the mounting surface caused the problem.
That sensor is just a coil with a metal core, I think it had around 450 ohm when I put a meter on it after I took it out. If that coil or the connectors are bad, the CEL would come on.
You can check the induced AC voltage on the connector when you raise both front wheels and spin the tires.

 

[thagan]

I will disconnect the sensor and check for 450 ohm. Do you know what the acceptable ohm range is? To check induced voltage, do I use a jumper on one side and put a voltmeter between other side, then with engine on, spin wheel? If so what is a proper increase in voltage? I will try scraping the rust at mount location. Do you know if the fluid that I shot in to clean ring off could cause problems, I just bought a 15mm 6 pt socket in hope of taking hub-plate off to drain fluid? Thanks so much...Todd

 

[pax]

You need to raise both front wheels off the ground in order to spin the wheel by hand since it's a 4x4. Block the rear wheels so the truck can't roll back on you. Don't start the engine. Put the transmission on neutral. Disconnect both sensor harness connector just behind the front bumpers, you should see two metal pins inside the connector on the side leading to the sensors. You need a helper to steady the digital VOM leads on the two pins while you are rotating the wheel by hand, put the digital VOM on the lowest AC Volt scale, the reading should be at least 0.3 AC volt at hand speed. If it is below that, remove the sensor to clean the mounting surface. Check the other wheel to compare the readings.
The resistance on the coil should be around 450 Ohms, that was the reading I had on mine.
If I understand you correctly, are you spraying cleaner inside the hole into the hub? You shouldn’t do that, that hub is suppose to be full of grease, I don't want anything in there other then grease. You should stick a piece of cloth to inside the hole while you are cleaning the rust and corrosions off the surface with a brush on a drill.
I read somewhere saying that, you can pump grease into the hole to replenish grease to the hub, I didn't do it though.

 

[thagan]

I will connect the meter the same to read volts as I do ohms (between the to pins). I probably can't come close to high speed by hand to reach 0.3 AC, any recommendations? I sprayed cleaner through the sensor hole to clean the ring that the sensor picks up on because based on some other postings but it never made sense to me that the grease should cause a problem because it is non-metallic...I hope I didn't do damage. Thanks for being so helpful!....Todd

 

[pax]

The idea is to get 0.3 volt or above on hand speed. You don't want to turn any faster. If you don't see 0.3 volt, you have to clean it.

 

[thagan]

I gave up and paid the cash cow $210 for two fromt abs sensors. First I checked the ohm of the old sensors and they were about 0.312 and voltage rose when spinning wheel. After cleaning sensor mounting surface off, problem was still present. Then put in two new sensors at about 0.420 ohm and problem is gone. I hope ford doesn't milk too many of you for THEIR DESIGN PROBLEM....Todd

 

[Hartman]

Should have gotten them on FPN at least.