Dear Tom and Ray:
In my infinite wisdom, I woke up early one Saturday morning and decided I would do something productive with my weekend. Even though I've never attempted any sort of car repair in my life, I decided to change the front brake rotors on my 2006 Ford Ranger. I bought all the tools necessary for the job, cranked up the radio and got the front passenger brake rotor replaced in just under 16 hours. NNNNNice! I took the car for a test drive, and the brakes did just fine, no issues. Then I moved on to the driver's-side brake rotor, which took just about four hours, given all the experience I'd gained on the other side. But then I had a problem: I went for a test drive, and my ABS system started to activate when I slowed down to under 2 mph or so. I can feel the pumping in the pedal and hear a bit of a humming noise. Well, that was about five months ago, and unfortunately, the problem hasn't worked itself out yet. I did some research, cleaned the speed sensors on both sides and checked to see if the reluctor wheels were the same as the ones on the old rotors I'd removed. They are. Not sure where to go from here. How can I figure out what I screwed up? Thank you.
Ray: Just out of curiosity, we did a survey of 527 normal people, and asked them at what point they would have given up on this job. Even the outliers walked away after five hours, Peter. And you should have, too!
Tom: Clearly, you're a person who needs to be watched carefully. But you probably knew that already.
Ray: There are two things you may have screwed up on your brakes. One is that you may have damaged the reluctor, or "chopper wheel."
Tom: The reluctor is a disc that spins along with the wheel. It has a series of notches on it, and the ABS wheel sensor uses those notches to determine how fast the wheel is turning. If you cracked the reluctor while replacing the rotors, for instance, it could be causing the wheel sensor to read the wheel speed incorrectly.
Ray: But a more likely possibility is that you damaged an ABS sensor (there's one on each wheel). You say you cleaned the sensors, but we've cleaned my brother, and it hasn't made him function any better. Sometimes things just need to be replaced.
Tom: What you need to do is try replacing the ABS sensor on the driver's side. It's an easy job, Peter. Twenty-five hours, max.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk Web site.)