Topic: Need help with brake problem

[sprinter]

This problem had my mechanic stumped stone cold so I thought I'd check with the folks here. 

I drive a 2000 Blazer.  Initially, I noticed the ABS kicks in just before the car comes to a stop.  This happens with no regularity, good weather or bad, hot engine or cold.  It usually is more pronounced the first time the brakes are used, say in the morning.  I know it's the ABS because I hear a whirring sound and the brake pedal kick back & forth as they do with ABS triggered. 

My mechanic thought it was a faulty ABS line but they all checked out fine.  The brake lines are ok as well. The brake fluid reservoir is full and there are no leaks.  Brake pads and the rotor look good too.

Lately, the whirring sound from the ABS unit has dissipated.  But just before the car stops, the brakes release lightly and quickly clamp down.  Almost like a 2-stage affair and not the typical ABS multiple brake & release cycle.  It now also happens every time I stop the car.   Other than this, the brake pedal goes way down in order to engage the brake.

Does anyone know what the problem could be? 

Thanks.

[mrthompson]

Sounds like an ABS wheel speed sensor, but it's just an educated guess.  Others will chime in with better answers.

Try pulling the ABS fuse and confirm if the problem goes away.

[blur911]

My old Audi was doing exactly the same thing, activating the ABS just before it came to a stop.   I assume it's a faulty sensor/hub. 
I pulled the fuse and it stopped.  I don't think it's a problem either way.

[Juke1]

Sounds like an ABS wheel speed sensor, but it's just an educated guess.  Others will chime in with better answers.

Try pulling the ABS fuse and confirm if the problem goes away.

I agree, the system sees the wheel as skidding, cleaning may be all that is required.

[johngenx]

Common problem on older Mercedes', and it's always a gone-south ABS speed sensor.  Cleaning would often buy some time, but once they began failing, you were sunk.  The Mercedes units were shockingly expensive (~$700 each) and quite DIY unfriendly to change, so on the old 190E I had, I just lived with no ABS.

[Accord Owner]

This is a common problem on GM cars of the era. It is usually the right front wheel speed sensor failing though occasionally the left one will go first . Eventually it will fail and trigger the ABS light. The good news is the part is reasonably priced for a Blazer.

[sprinter]

Thanks everyone.  I will ask my friend to take a closer look on the sensors.

[sprinter]

Pulled the fuse and voila!  The problem is gone.  Will be getting the sensors replaced.  Thanks everyone.

[mrthompson]

Ah, the power of the internets.   

[ktm525]

Pulled the fuse and voila!  The problem is gone.  Will be getting the sensors replaced.  Thanks everyone.

Why bother? Earlier generations of GM ABS were pathetic. Perhaps by 2000 they may have got better.

[mrthompson]

Perhaps sprinter prefers to have working ABS?  Some people have only driven ABS equipped vehicles and removing the functionality of that feature might not be a wise move.  Even though GM ABS systems of a certain vintage are not reliable, a few hundred dollars here and there is much cheaper than a collision repair.   

[ktm525]

Perhaps sprinter prefers to have working ABS?  Some people have only driven ABS equipped vehicles and removing the functionality of that feature might not be a wise move.  Even though GM ABS systems of a certain vintage are not reliable, a few hundred dollars here and there is much cheaper than a collision repair.   

The early GM ABS systems were downright dangerous. GM had a push in the mid nineties to have ABS on all its vehicles. A system on a friends Sunbird was so slow that the braking distances in sniow/ice/wet/dry improved by removing the fuse. It cycled so slow.

[mrthompson]

Holy shnikes!