For a while now the brakes on my 98 Lumina have been clicking horribly when you're braking and are below 30MPH. I am well aware that clicking is somewhat normal at times especially if you're losing traction. However this is constant. This happens all the time. It is definitely not normal.

Anyway, this finally was bugging the hell out of me so much today that I popped the hood and unhooked a couple.... "sensors" on top of the master cylinder. I'm not sure if they're sensors or what, that's why I'm here asking. They quite possibly may be the little motors that pulsate the brake fluid around to each tire as needed. But after I unplugged both of these my problem went away. Of course the anti-lock light is illuminated on the dash, but no more clicking like crazy!! So my few questions are:

1. What exactly did I unplug, and is it safe to continue like this for a little while?

2. Any idea what my exact issue is? Will I need to replace the whole master cylinder?

My theory is that what I did unplug is the little valve or motor that controls this, and my problem is likely one of those motors. Like it's constantly activating when it shouldn't be.

I'm including a picture showing what I unplugged. This isn't a picture I took, but it looks pretty similar to mine.

Thanks for any replies.

http://img262.imageshack.us/img262/2539/446e1eu2.th.jpg (http://img262.imageshack.us/my.php?image=446e1eu2.jpg)

Ace,

Those are solenoids, and are used in conjunction with the motor to modulate pressure to the brake hydraulic systems. They typically only operate when the Electronic Brake Control Module commands some activity from them, although they may actuate briefly when the ignition is first turned on and the system initializes.

The EBCM is designed to act only if a wheel sensor reports slippage, or uneven rotational speed between the wheels during braking.

The fastest way to locate the problem(s) is to scan the ABS control system with a compatible scanner and retrieve the stored information. Short of that, about all you can do is test and verify the wheel sensors one at a time, test the brake pedal switch, meter the power and resistances at the ABS power relay, and check the solenoid resistances.

Most problems with ABS systems are related to the wheel speed sensors, switches, or relays external to the control module. That doesn't necessarily mean that a sensor has failed, but that the EBCM is not receiving the correct signals. I've had several which have been connections at the wheel sensors and not problems with the sensors or tone rings themselves.

Reconnect the solenoids, then turn on the ignition. The ABS lamp on the instrument panel should turn on for about three seconds, then turn off. Upon starting the engine, the ABS light will again turn on for about three seconds, then turn off. That is the normal cycle. If the lamp remains on, there is a fault in the system. How is your's acting?

Thanks for the quick reply and letting me know what I unplugged. The very first time I started noticing this I was thinking about the speed sensors at the wheels. I figured one had gone bad and kept thinking there was slippage so it was engauging the abs. At first it wasn't happening a whole lot, but now it's constant. Once you hit the brakes and you're below 30MPH it's just constantly clicking. Though it's odd because you can't actually feel it in the pedal like you would...say when you're slipping on ice. When you brake on ice, you can feel the pedal pulsating which is perfectly normal. So I don't know, it's odd. I'll plug those back in tomorrow and see how it acts.

Also, about the anti-lock light. Right now it's constantly lit because I unplugged those solenoids. When I had them plugged in I never got the abs or low traction light. That's the other thing that was odd. When you're slipping on ice and the abs kicks in, you hear/feel the abs and you get the low trac light on. When you're braking normally and I'm constantly getting this clicking I get no low trac light or an abs light. It seems like if the system was constantly thinking there was slippage, it would have the low trac light come on.

You also mentioned scanning the ABS system for any stored info. My dad has a pretty nice code reader and the only thing I've ever gotten as far as codes go is the cam shaft sensor.

Your problem is getting to be more and more common...this is about the fourth or fifth time I've heard this with the exact same symptoms in the last six months or so...but I don't have an answer...

But being like you said that the lights don't indicate ABS actuation, even though the system is obviously active makes me wonder about the control module...wheel speed sensor faults usually just make the ABS light come on, and the system defaults to normal non-ABS operation, but this is something different that's happening more and more as these get older, apparently.

Please post when you find out what it was, so we'll know next time.